Seed
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Plants invented survival + prop. units called Spores & Seeds A seed is a small, but complete embryonic plant enclosed in a seed coat, usually with some stored food (exception the smallest orchid seeds). It is the product of the ripened female ovule and the fertilizing male pollen and hence a product of sexual propagation with its genes-mixing effect increasing the genetic diversity of the offspring. Other plants have a propagation unit called spore. A spore is a reproductive unit for dispersal and surviving unfavorable conditions. Spores form part of the life cycles of many bacteria, algae, fungi and lower plants like mosses and ferns. The difference between spores and seeds is that spores have very little stored food resources compared with seeds. Fern sporangia called sori are packages containing many spores or Lower Plants or Vascular plants . Subkingdom Bryophytes -----------------------------------------------------------------------Subdivisions Divisions Fern Allies Pteridophyta = Coniferophytae ------------------------------------------------------------------------- Subkingdom Tracheophytes Coniferophyta and Magnoliophyta Seed Plants Embryophyta Flowering Plants = Magnoliophyta The sex life of mosses Members of the kingdom Fungi propagate by spores. These look like those, single-celled units that germinate into a mycelium network of filaments Also lower plants = bryophytes propagate by spores, single-celled units that germinate into a protonema network of green and rhizoidal filaments The capsule is under tension when dehydrated and ruptures with force. This force ejects thread-like dead structures called elaters. Before the rupture the elaters were coated in spores and attached to the capsule wall. The elaters are like little wings that fly away with the wind to ensure the propagation of the bryophyte species The spores of Ferns The spores of true ferns are organized in sporangia and these sporangia are organized in a cluster called sorus (plural sori), which are attached to the lower side of the fern leaves called fronds. In the Pacific Northwest, fern spores ripen from late May through October and will waft off like fine dust during this period. The fern spores develop into little heart-shaped tissues that are called prothallium. They carry both sperm- and egg-producing units at different locations. Misting the prothallii will help fertilization and from the prothallium we will see the arising of a horizontal rhizome =stem and erect leaves. This is a sporophyte of a higher plant. How the spores are launched into the air … The spores of true ferns are organized in sporangia and these sporangia are organized in a cluster called sorus. Here you see how these sporangia rupture and release the spores. 1. The sporangia mature and dehydrate by evaporation. This puts the cells of the outer ring (annulus cells) under enormous tension. 2. The annulus ring will eventually give and rupture so forcefully that it will throw the spores away from the mother plant. The spores of horsetails Horsetails are higher plants belonging to the fern relatives or Pteridophyta. In the spring they first drive fertile shoots and later vegetative ones. The fertile shoots look a minaret and end with a strobilus that is studded with sporangia. When the sporangia dehydrate a small touch or wind will launch the spores ... The horsetail spores have 4 thread-like extensions that when dry act like wings for flight or alternatively under humidity coil around the spore to lower the lift and increase the sink rate to force landing in wet areas (meadows ok but lakes not so good) How to grow ferns from spores The spores of true ferns are organized in sporangia and these sporangia are organized in a cluster called sorus (plural sori), which are attached to the lower side of the fern leaves called fronds. To gather the spores, pick a frond or portion of a frond and place it between two sheets of white paper. If ripe, the spores should drop within 24 hours 7 will leave a pattern on the paper. The spores are then ready to be sown. I use a clear plastic container with a moist sterilized compost mix. The spores are dusted on the top of the mix and the lid on, then placed under cool white fluorescent lights that are on for 14 hours. spores should not be indirect sunlight. after several weeks a thin, green haze will form on the mix. This will grow into a carpet of prothallia, - small, green, heart-shaped structures and contain the sperm and the egg. When the prothallia are approximately ¼ inch, they should be lightly misted forfertilization I then move small clumps of prothallia/sporelings to a mix of peat, vermiculite, & potting soil in a covered mini-greenhouse. You find this on many sites like http://www.hardyferns.org/fern-info-propagation.php) The wettability of Spores One of the technically most intriguing propagation bodies are spores of Lycopodium (ground pines). When shipped they have to be marked as highly inflammable or even explosive. Lycopodium is a genus of clubmosses (ground pines or creeping cedar), in the family of fern-allies (see Pteridophyta). Specialized leaves (sporophylls) bear reniform spore-cases (sporangia) in the axils, which contain spores of one kind only. The clubshaped capsules give genus its name. The spores of Lycopodium species are harvested and used herbally as Lycopodium powder or “witch flour” 1. Fill a 50 ml beaker with water & cover surface with Lycopodium powder. Stick your finger into the water & then pull it out. What do you observe? 2. Lyco spores are as rich in essential oils as parsley seeds although nobody seems to care. Blow a knife-tip full of witch flour into a gas flame! Gently! Development Cell division and expansion are particularly simple & fast in plants Most embryos start with a fused cell called zygote- a fertilized ovule. Most higher plants start their life as an embryo contained in a seed or a vegetative prop unit. Most higher plants start their adult life as germinating seedlings Plants reach sexual maturity by flowering & subsequent seed production E. Haeckel’s biogenetic rule” “ Ontogenesis repeats phylogenesis” Î plant seedlings look very much alike in the monocots or dicots! The sex life of higher plants Plant sexuality covers the wide variety of sexual reproduction systems in plants. Christian Konrad Sprengel (1750–1816) was a German theologist, teacher, naturalist& discoverer of plant sexuality. S. was born in Brandenburg an der Havel. After 1787, S. did research on pollination & interaction between flowers & insect visitors: Das entdeckte Geheimnis der Natur im Bau und in der Befruchtung der Blumen (Berlin 1793), he was the founder of this new discipline. Unlike animals, plants are immobile & cannot actively seek out sexual partners Î bird, insects, wind The majority of higher plants (90 %) contain both male (stamens with anthers & pollen) & female (style with ovary & egg cells) organs = hermaphrodites Monoecious – have separate male & fem. reproductive units (flowers, conifer cones, Etc.) on the same plant; from Greek for "one household". Alder , corn , cucs, pumpkin Dioecious - having unisexual reproductive units with male & female individual plants. Different flowers, cones, etc. occuron different individuals; from Greek for "two households". E.g. holly, Gingko, Salix willow, Aruncus = goatsbeard, Urtica dioica, The sex life of plants Ancient peoples were not so innocent or ignorant about plant sex. This plate from the temple of Karnak shows honeybees pollinating flowering rushes .. You see the Ancient Ankh symbol of eternal life, that shows clear similarities to the later appearing Christian Cross next to the ancient Di symbol (arrow shaped bread cone symbolizing offer) and a bee sitting next to what we may take as a flower – the Su symbol for a rush that is flowering. (1) The ancients knew about the role of insects for the fertilization of flowering plants. (2) They also knew about pollen as the necessary agent of fertilization. They pollinated themselves imported plants that were not pollinated by the local insects (3) This knowledge – like so many others – was lost in time. Pollen – flying male gametes that replace outdated sperms Pollen germinates on stigma of only his own species, otherwise there would be chaos in the plant world. How higher plants reproduce! How higher plants reproduce, Pollen & Ovary Lily Pollen This is the male world - a close-up of an anther at the end of a filament A lily has 3 petals and 3 sepals, 3 pistils and 3 filaments Here is a close-up of lily pollen resembling wheat grains Orchid Pollen Orchids developed a complex mechanisms to achieve cross-pollination . Charles Darwin described in his 1862 book Fertilisation of Orchids. The pollen is organized in a single package called pollinium, which is attached to the head of a insect. It now becomes very important for the orchids since it can pollinate thousands of orchids. Because of this, orchid flowers usually remain receptive for very long periods (i.e. as long as unpollinated they make a lasting present). The pollinia stick to your hand as well as a bee! Orchids made their flowers smell and look like female bees to increase their chances of pollination. Mimicry at its best. Î How Pollen germinates Pollen grain has 3 nuclei 1. A bigger one that drives the tube growth 2. 2 smaller sexual nuclei that fertilize either the ovule or the polar cell to give rise to embryo and endosperm respect. Pollen germinates only in a highly osmotic medium (in water it bursts 7 is destroyed). It also germinates only on the stigma of its own species, in non-selfing species only on the stigma of a different plant individual. Pollen does not carry chloroplasts or proplastids Since pollen does not carry them, all chloroplasts come from the mother plant as shown by maternal inheritance as shown by variegated mutants of the four-o-clock plant Mirabilis jalapa branch from egg parent (♀) Phenotype of pollen parent (♂) Progeny White White White Green Green Variegated White Green Variegated White Green Green White White White Green Green Variegated, Variegation is an attractive horticultural feature with white or yellow coloured zones on the leaf.. It is due to some of the plant’s meristematic tissue losing the ability to produce chloroplasts, so that the tissue it produces is no longer green. Artificial fertilization in plants Artificial pollination (i.e. by humans does not strike us as strange as artificial insemination in cows etc. since plant are pollinated by other creatures anyway. Date palms and vanilla plants have been-hand pollinated ever since we know about them. Also Mendel strictly hand pollinated his peas in order to get pure-bred lines & clean crosses. Embryo development: double fertilization Fertilization in higher plants is different from lower plants and animals. The pollen has 3 nuclei rather than one: one to drive pollen tube expansion, one to fertilize the egg cell and form the embryo and one to fertilize the polar nucleus to form the endosperm Seeds – units of sexual propagation Seed (kernel) is a small embryonic plant enclosed in a seed coat together with stored food supply. It derives from the ripened ovule of gymnosperm and angiosperm plants after fertilization. Seeds do not appear like anything we are familiar with in the world of higher animals. The next best thing is perhaps the egg which is common among most invertebrates and vertebrates like reptiles and birds. Seeds are the most powerful means of propagation of higher plants (embryophytes), much more so than the spores of lower plants. They are a means to attract and create food dependences of seed-distributing animals like the humans (see Michael Pollan: Botany of Desire). Seeds can be small: Begonia 1 oz – 106 seeds or big: 1 coconut = 15 lbs. All seeds have requirements to be met before they germinate. Most basic ones are humidity and agreeable temperatures. Hardy annual seeds like Calif Poppies, larkspur etc. germinate in the fall with seedlings that are able to survive the winter Bizarre Plants: the largest & weirdly shaped seed Maldives or Seychelle Islands : source of unusual seed coco-de-mer seeds first mistaken as eggs of griffins (Georg Eberhard Rumpf 1682 named it Cocus maldivicus): most important aphrodisiac & antidote like the benzoar (ideal goblet material). Rudolf II German Emperor (1650) payed 4000 florins = 5000 gold thalers (dollars) for a seed 1742 French landed from Mauritius, 1768 that the islands interior was explored & confirmed as the source of coco-de-mer, the Seychelles’ nut Lodoicea palms (daughter of Troy’s Priam difficult to germinate; first Kew RoyalGarden plants were pre-germinated in Seychelles & then grown in 1854 , hurrah ==> a yellow horizontal shoot projects parallel to soil surface for 3 m before horizontal shoot develops & root grows. Horizontal shoot rots away & seedling cannot be traced back to seed. Jelly-like endosperm of nuts is a delicacy for the rich. “Surely, Sir, it is Priam’s daughter” Seed Size Seeds derive from the zygote & are encapsuled in fruits (derived from ovary). They are infinite marvels in size, shape, mode of distribution etc. Coco-de-Mere Seychelles nut Catalpa pods Aesculus glabra American chestnut winged Catalpa seed Cattleya fruit & seeds a tropical orchid Paulownia capsule & seeds Monocot seeds have endosperm Zea mays Triticum sativum wheat Beta vulgaris beet Dicot seeds have cotyledons Embryos of plants look different from those of animals. But like the later any similarity to the adult parents is only a matter of flattery. Animal embryos at maturity Bean Phaseolus vulgaris coconut embryo at maturity Embryo Size Variability in size and shape find little interest with gardeners etc. who hardly ever take a look below the fruit/ seed level Beta vulgaris beet Ricinus communis pine Pinus Embryo Size - Dicots Gingko biloba Pea Pisum sativum Phaseolus vulgaris Avocado Persea amer. Red Pepper Capsicum Onion Alium Most stunning Embryos the world has ever seen Seeds come in dispersal units: embryo , food supply, coat, plus parachutes: lettuce (Lactuca) dandelion (Taraxacum), thistle (Cirsium) wings: maple Acer, alder Alnus, tumbleweeds floats: coconut bribes: beans, bloodroot etc carry elaiosomes or oil bodies for ant-dispersal glues: mistletoes, squirting cucumber The message in a seed is hope? Elaiosomes Elaiosomes (Greek élaion "oil“) are external structures attached to the seeds of some plant species. They are rich in lipids like linoleic acid , which serves as volatile signal (either “dead ant” or “offspring” to attract ants to bring the seeds to the ants nest. Here they are protected from predation and can germinate in a dark and wet place …………. The message in a bloodroot seed with elaiosomes is: “Dear ant! Carry me into your nest where it is moist and dark and safe for seeds to do what they do best: germinate into a plant” Mimetic Weeds Human culture contains crop plants: wheat, millet, rice , corn , flax, hemp, soy, rape, cotton. All these are ruderal plants, i.e. they like N, + they have tendency to luxuriate, i.e. they adopt a larger size. Humans increase tendency by selecting the larger plants (conscious selection). Humans also select against useless weeds by eliminating them. Weeds, however, outsmarted humans and their selection by several methods; one being mimicry: change in seed shape + to premature seed dispersal WEED Plant imitated CROP Plant Comelina gabrata flax Linum usitatissimum to C. sativa linicola Rye Secale montana Î cereale wheat Triticum aest. Oats Avena fatua wheat Triticum aestivum Wolfgang Wickler (1974) Mimicry in Plants and Animals. McGraw-Hill, N.Y. Humans often failed to adopt smart designs ! Which flying seed did “Homo sapiens” choose to simulate? serial production of motor plane “Taube” 1912 a STOL training plane nearly impossible to stall. The flying Zanonia fruit served as a template for the first non-stalling airplane trainer (STOL) Zanonia macrocarpa (Syn. Macrozanonia macrocarpa (Blume) Cogn., Alsomitra macrocarpa M.Roem.) alias Javan cucmber is a vine in the cuccurbitaceae. The fruit - a maplelike samara - has thin dry wings with 13 cm wing span and can fly distances of up to 50 m. The plant was first described under the name Zanonia macrocarpa in 1825 by Carl Ludwig Blume This principle was used to build a monoplane in 1903 in cooperation of botanists with the Austrian airplane pioneer Ignaz Etrich (a designing strategy today called biomimetics) and in 1912 the motorized glider “Taube” which had a stall speed of less than 10 mph (idiots could fly this one). Unfortunately this design was not fit for tight turns – the developing strategy of fighter planes Í The “Taube” of the famous Lieutenant Plüschow was the only plane of the Imperial Navy in Tsingtao, in 1914 a German colony in China. Before Tsingtao was overwhelmed by superior numbers of Japanese & British ships & troops he flew his badly damaged plane for 250 miles into China & continued on foot The betel nut is the seed of the Areca catechu Palm The areca nut is the seed of the Areca catechu palm, which grows in the tropical Pacific, Asia, and parts of east Africa. It is commonly referred to as betel nut, because it is often chewed wrapped in betel leaves (paan) Research on Cancer found that this widespread habit of chewing areca nut is carcinogenic. "About 88 percent of those who suffer from oral cancer in Taiwan are betel nut chewers. Various carcinogenic compounds are present in the nut, most importantly arecoline – a substance also released from microwaved butter and fats., The areca nut has a fibrous inner core that is chewed and produces a red color that is visible on the teeth. Women were especially lured to chew betel nuts because the juice would stain their lips a pretty red hue. The betel nuts stain the gums red – they contain an interesting red Areca dye that remains to be identified. Seeds are tools of identification – sunflower family Many seeds of the Asteraceae often have bristles making them resembling a shaving brush. Why? The flowers sit on a disc surrounded by the bracts. After pollination, the seeds grow and mature until they are ripe and ready to be dispersed. In some species, the bracts surrounding the flower simply open and allow the seeds to be dispersed by the wind. In this case, the seed is often attached to its own 'parachute', as in the Dandelion. In other species, the bracts close over the disc while the seeds mature, and to be dispersed, they simply separate from the disc. Seeds of this family are oval and may be flat or rounded. They can be straw-coloured, warm brown or nearly black. Seeds are tools of identification – Geraniaceae family Actually, it is the seeds that gave this family its name. Geranos is the Greek word for a crane, and most of the seeds in the family have a long pointed 'beak' at the seed capsule. There are usually five seeds and they are twisted together with the fibers of the 'bill' in the centre. When the seeds are ripe, the five chambers separate from one another explosively, held on to the 'bill' at their tips, and the seeds are flung from the seed capsule. Seeds are tools of identification – Rosaceae family The fruits of the Rosaceae can be follicles, capsules, nuts, achenes, drupes, and accessory fruits, like an apple, or the hip of a rose. The seeds are equally variable and many of them contain Amygdalin which can be converted to cyanide during digestion Acanthospermum seeds – a bizarre seed in the Rosaceae Î A brain-like surface structure is found in Raspberry (Rubus idaeus) seeds Î And in Potentilla and Cinquefoil seeds Coconut Palm Palm seeds come in a huge variety of sizes and are mostly round. One of the largest is the coconut. Here we see how the meat (being a cotyledon-like organ) absorbs the liquid endosperm. The embryo is a minute ball in the endosperm situate directly in the living pore. A special type of… fruits are the nuts A nut is a fruit composed of a hard shell in addition to embryo and food, which is indehiscent = the dehydrating fruit does not open to release the seed. Nut fruits occur in many and various families. Many nut embryos valuable vegetable oils (walnut, hazelnut, coconut). The walnut Juglans ssp. Î What you eat are the two cotlyedons of a typical dicot embryo. Shame on you. Other Weird Seeds Trapa natans or Bull’Horn or water caltrops are a species in the family of the water chestnuts. The seeds are 6 cm in diameter and look like a Bull’s head. The species are floating annual aquatic plants, growing in slow-moving water up to 5 meters deep, native to warm temperate parts of Eurasia & Africa. You could buy water chestnuts in markets all over Europe until 1880. The nuts were offered roasted, just like sweet chestnuts (Castanea sativa Mill.). In all Europe water chestnuts were used for human food. Today it is a rare plant. Do not eat them raw because they contain a harmful parasite. Just steam or boil them in water, add some salt and crack the shell to reveal a creamy flesh. The water caltrop's submerged stem reaches 12 to 15 ft (3.6 to 4.5 m) in length, anchored into the mud by the roots. It has finely divided feather-like submerged leaves borne along the length of the stem, and undivided floating leaves borne in a rosette at the water's surface (aquatic heterophylly). The fruit is a nut with four 0.5 in (1 cm), barbed spines. Seeds can remain viable for up to 12 years, although most will germinate within the first two years The betel nut is the seed of the Areca catechu Palm The areca nut is the seed of the Areca catechu palm, which grows in the tropical Pacific, Asia, and parts of east Africa. It is commonly referred to as betel nut, because it is often chewed wrapped in betel leaves (paan) Research on Cancer found that this widespread habit of chewing areca nut is carcinogenic. "About 88 percent of those who suffer from oral cancer in Taiwan are betel nut chewers. Various carcinogenic compounds are present in the nut, most importantly arecoline – a substance also released from microwaved butter and fats., The areca nut has a fibrous inner core that is chewed and produces a red color that is visible on the teeth. Women were especially lured to chew betel nuts because the juice would stain their lips a pretty red hue. The betel nuts stain the gums red – they contain an interesting red Areca dye that remains to be identified. Liquid endosperm – eating like the plant embryo Coconut milk is well-known to any kid from the Caribbean. Together with rum it is the universal ingredient of drinks there. When botanists started to try to grow embryos outside the seed on agar cultures they also first relied upon liquid coconut endosperm as the secret ingredient for success. However, the taste of coconut endosperm is not particular attractive when compared to drinks made from the endosperm or cotyledons of other seeds; say walnut hazelnut or almond. How to make almond, walnut or any seed milk! 1.5 cups whole blanched almonds or other whole raw almonds or walnuts or hazelnuts, better when soaked for 12 h •Add 1.5 cups of water and blend, add to a total of 4 cups water • Strain through chasse cloth (optional) and add 1 tsp vanilla extract plus 1.5 tbsp maple syrup or honey and a dash cinnamon (for diabetics) Secret Plants of China: Rice Paper 1842 Treaty of Nanking opened China’s interior to Western explorers Robert Fortune 1812-1880 job to find plant of “rice paper”, orange CumQuat, tea pl, “Peaches of Peking” dressed as Chinese. the boughs are boiled and freed from bark. cylindrical core of pith is rolled on a hard flat surface against a knife, by which it is cut into thin sheets of a fine ivory-like texture. Dyed, this paper is used for artificial flowers, while the white sheets are employed for watercolor drawings. It is not suited for writing. Tetrapanax papyriferus (Tung-tsau or Ricepaper Plant) is an evergreen shrub in the Araliaceae from the swampy forests of Taiwan, often planted for a tropical effect against walls. The thick stem pith was used to make Chinese rice paper. In Europe, around the 1900s, a paperlike substance was originally known as rice paper, due to the mistaken notion that it is made from rice. Rice paper usually refers to paper made from parts of the rice plant, like rice straw or rice flour Secret Plants of China: Cumquat Robert Fortune 1812-1880 job to find plant of “rice paper”, orange CumQuat, tea pl, “Peaches of Peking” dressed as Chinese. Kumquats are small fruit-bearing trees in the family Rutaceae, either forming the genus Fortunella, or placed within Citrus sensu lato. The edible fruit closely resembles an orange (Citrus sinensis), but it is much smaller and ovular, like an olive. The kumquat tree produces 30 to 50 fruit each year and can be hydrophytic, with the fruit often found floating on water near shore during the ripe season. he cumquat may be served fresh if quite ripe, peeled or unpeeled. It may used for garnishing fish or meat platters. It can be preserved or made into marmalade. Secret Plants of China: the Tea Thief Robert Fortune 1812-1880 job to find tea pl, By 1840 the West had become enchanted with a new brew, tea. But, China held the monopoly on its trade and manufacture, which it had fiercely guarded for more than 5,000 years. Camellia sinensis is an evergreen shrub whose leaves are used to produce Chinese tea. genus Camellia in the family Theaceae. White tea, green tea, oolong, pu-erh tea and black tea are all harvested from this species, but are processed differently. Kukicha (twig tea) uses twigs and stems rather than leaves. Tea plants are propagated from seed or by cutting; it takes approx 4 to 15 years before a new plant can be harvested Two principal varieties are used: the China plant (C. sinensis sinensis), used for most Chinese, Formosan and Japanese teas (but not Pu-erh); and the clonal Assam plant (C. sinensis assamica), used in most Indian and other teas (but not Darjeeling). Annuals Annuals are short-lived plants which has germinate, grow, flower and seed in one season. They produce many but small seeds for survival of winter etc. Among annual plants are the cereal grains of the world, the peas, beans, soybeans, the sunflower Helianthus annuus, buckwheat, flax, jute, tobacco, Chenopodium quinoa, Lupinus, i.e. they produce sizeable seeds. but also many flowers like Althaea, Amaranthus, Borage, Calendula, Centaurea cyanus, Cosmos, Dahlia, Datura, Eschscholzia, Lathyrus, Papaver somniferum The importance of seeds for the survival of annuals 1. It is vital for annuals to flower and produce seeds. Otherwise the genes of this trait are wiped out forever. 2. One strategy to increase the chances of survival is to produce seeds that germinate not in the next year but after varying number of years, e.g. after 1, 3, 5, or 30 years. Such plants are hard to get rid of. Annuals ………. are plants you that you plant with seed every spring Biennials Biennials normally do not bloom until the second year but just form a rosette of leaves feeding a suberrarean organ like bulb, rhizome, storage root Many garden plants like beet, celery, cabbage, carrot, turnip, spinach, lettuce, but also many flowers like Borago officinais, Chelidonium majis, Digitalis purpurea, Isatis tinctoria (woad), Lunaria annua, Myosotis sylvatica (forgetme-not), Verbascum thapsus Perennials Perennials are plants that live longer than biennials, i.e. > 2 years. They are either woody (trees shrubs vines) or herbaceous perennials. The herbacious perennials survive winter as subterranean organs like roots or stems (rhizomes, colons, bulbs, etc.). Many perennials produce large seeds and with it larger seedlings that quickly develop leaves for photosynthesis. Annuals produce many more seeds but smaller seeds per plant. Many garden plants like asparagus, banana, rhubarb, lupines but also many ferns, liverworts and grasses but also many flowers like Epilobium (fireweed), rue Ruta graveolens, peonies, delphinium, primula, dahlia, orchids, begonia etc. Garden or flower perennials Perennials Seed germination in monocots & dicots Mechanism of seed germination in corn How is the dormancy period of seeds overcome? 1000 answers : the embryo is in a semivital fakir stage with no detectable respiration. 1. step: Water enters the seed and is taken up Î enzymes are activated & respiration starts. Corn is domesticated; no internal dormancy 2. Hormone GA (gibberellic acid is released from embryo & goes to aleurone cells 3. Aleurone cells produce & release @-amylase into endosperm where it digests starch into sugar 4.Sugars are taken up by embryo and fuel growth processes 5.Primary meristems are activated , cytokinesis and growth starts with root tip exiting the seed coat Seeds – requirements for germination Germination is the process in which a seed or spore emerges from dormancy This involves the sprouting of seedlings from a seed (angiosperms, gymnosperms) & sporelings (protonema, heart-shaped prothalli) from spores (bryophytes & Ferns) Seed germination requires: (1) Water. Dormant seeds have water contant of approx. 10 %. Hydration activates the enzymes & increases the internal pressure of the seed to burst out of his coat. (2) Oxygen is required for aerobic respiration, the source of energy for the seedlings. I f a seed is buried in waterlogged soil or has an oxygenimpermeable coat , it will not germinate. (3) Temperature. Seeds will not germinate above or below their temp. range. Most seeds germinate slightly above room temp (16-24 C). Some seeds require cold temp. (vernalization) to break their internal dormancy. (4) Light: dill, lettuce & poppy seeds require light, cucurbits darkness What triggers the germination of coconuts? Coconuts float in ocean water at warm temps. Why do they not germinate? My question is how does a coconut seed (Cocos nucifera) "know" it is not floating around in a salty environment, and take in fresh water? What stops the seed from germinating while it is floating for weeks or months in the ocean?. Does the hard endosperm have a salt sensor? A "movement sensor" to indicate it has stopped floating, a "gravity sensor" to show it is no longer pointy end up? I would like to hear from anyone who has successfully germinated a coconut seed, how long it took and what happened. I put forward the following hypothesis: (1) coconuts are filled with the embryo and liquid endosperm. The liquid leaves an air bubble which keeps the nut floating in a particular position, the eyes up, preventing the uptake of water. Or, nuts are unable to take up water from the ocean (osmosis). How to test the hypothesis? You incubate one coconut in either warm fresh or warm salt water and test for germination. The experiment should be done in the sun and with warm summer temperatures around. How to germinate coconuts? Our retail stores carry only coconuts where the fibrous hull has been removed. Can they still be germinated? According to this video they can. http://www.youtube.com/watch?v=BieelvE_ZPIPI Choose dehulled coconuts with lots of liquid indicating freshness Incubate them for 2-3 d in warm water Drain the water but create a humid and warm environment (we will improve on the cheap Ziploc bag) Check for changes induced by hydration! Can you already tell in this stage which eye is the active one that will produce a shoot? Watch the coconuts every week for the rest of the labs looking out for this particular sign of germination Î Coconuts are monocots and as such will germinate like with the shoot inside a protective sheath called coleoptile After 2 months (depending on temp ) we would expect to see shoot-born roots Î and finally the shoot greening (see top picture). It is an adventure! Ahh, the internet – aside from plenty BS sometimes allows you insides into a problem ….But which is it? http://www.youtube.com/watch?v=BieelvE_ZPI A germinated coconut drifts in Palau's inner lagoon. The coconut will hopefully wind up on a sandy beach where it can mature. coconut (Cocos nucifera) floats in shallow water in French Polynesia. Plant dormancy – Seeds & Buds Plant embryos are always put into dormancy at the end of the embryogenesis to prevents germination on the mother plant Î vivipary Def.: Viable seeds that do not germinate are said to be dormant. When a mature, viable (embryo cells alive) seed fails to germinate under favorable conditions (water, temps), it is dormant. 2 types of dormancy Î 1. seed coat dormancy or external dormancy is caused by the presence of a hard seed covering or seed coat that prevents water and oxygen from reaching and activating the embryo. 2. embryo dormancy or internal dormancy, is caused by inhibition of the embryo which prevents it to germinate under increased hydration In the dehydrated (< 10 % water) state of dormancy, the embryo can survive extremely hot or cold temperatures (300 C for a short time), radioactive radiation is not causing genetic mutations. Î Therefore annuals survive adverse environments like winter or drought as seeds How to overcome seed dormancy! Wild plants have exceeding long periods of dormancy, domesticated plants do not. Dormant seeds were abolished during the selection process of harvesting and sowing the next year. There are several ways to overcome the dormancy of seeds. Scarification is artificial damaging of seed coat to allow access of water. Use of file (mechanic sc.) or 10 min soak in con. Sulfuric acid (chem. S) Stratification: cold treatment simulating the winter frost. Seeds are mixed together with moist sand or peat moss and stored for a few weeks in the refrigerator (4 C or 40 F). This treatment starts a process that breaks down abscisic acid and inhibitors of embryonic development. Seed Banking refers to the fact that some plant species (weeds, Scots broom) have many generations of seeds in the soil. A variable length of the dormancy create seed banks, which allow them to germinate even if the previous years did not set seeds or even if the plant was destroyed years before. Seeds – requirements for germination: water, temp, air All seeds have requirements to be met before they germinate. Most basic ones are humidity & agreeable temperatures. If you plant seeds , they require a porous and well-drained soil. If you “puddle the soil”, i.e. stirring it when wet – you remove air spaces + oxygen needed for germination Hardy annual seeds like California Poppies, larkspur Delphinium etc. are sown in late summer, germinate in the fall with seedlings able to survive winter Biennial seeds such as hollyhook Althaea,Bellis perennis, Campanula, Digitalis, Myosotis (forget-me-not), Verbascum mullein, Viola Pansy sown from June to August Seeds of hardy perennials are sown late April to early May. They will flower and make seeds at the end of September. Columbine Aquilegia, Bleeding hearts Coreopsis, Gas-plant Dictamnus, Christmas-rose Helleborus, Flax Linum, Lobelia but not hybrids like Phlox, Peones etc. Inhibitors of seed germination Malus pumila. Seeds of apples will not germinate when surrounded by placental tissue of the fruit. Other berries also have inhibitory agents in the fruit Fir or Abies species have inhibitory dipenten in the seed vesicles Sunflower Helianthus tuberosus seeds have substance called heliangine Bean seeds Phaseolus vulgaris contains Phaseic acid. 1963 cotton seed was extracted the inhibitory substance found was sesquiterpenoid called abscisin II. 1969 leaves of decidious trees were extracted and the abscision-causing substance was a sesquiterpene called dormin. It was identical with abscisin II and from now on called abscisic acid Ref: Evenari M (1949) Germination inhibitors. Bot reviews 15: 153-194 Inhibitors of seed germination Stimulation phase: post maturation of embryo occurs in the seeds of Tilia cordata, Acer, Fagus sylvatica, Rosa canina); sometimes also with embryo growth (Fraxinus, Gingko). Chemical inhibitors in endosperm and skin around skin around the seeds (apple). Abies has dipenten in the vesicles, berries have inhibitory agents in the fruit Most common inhibitors are coumarins and Abscisic acid. Inhibitors of seed germination: Allelopathic Exudates Many plants, especially invading newcomers from the old world are plants that use germinationinhibiting root exudates to stop the germination and growth of other neighbors Î allelopathy Such plants include walnut, chickweed, knapweed, garlic mustard, sagebrush Artemisia tridentata, and many more plants. Ivy Hedera helix ground cover enforces a “noman’s-land” zone upon neighboring wild flowers Straw from oats Avena sativa when left on the field has proven to inhibit the germination of many other plants including aggressive weeds. Seeds - germination Many wild plants evolved natural mechanisms to keep seeds from sprouting: dormancy Wild seed does not germinate easily (seed banks lasting > 50 a), domesticated seed do. Easy, simultaneous germination of all seeds is a hazard for a wild plant species’ survival Temperature Germination of alpine Trillium nivalis (Europe), after 1. winter : root after 2. winter: shoot Harry Borthwick’s Water Leaking of chemicals famous experiment (1952) shows that some seeds need light and others need dark to germinate Stimulators of seed germination Hydration phase: older seeds lose power to absorb H2O; normal embryo humidity 5 to 90 % stage with no detectable respiration. :increases the embryo is in a from semivital fakir Stimulation phase: post maturation of embryo occurs in the seeds of Tilia cordata, Acer, Fagus sylvatica, Rosa canina); sometimes also with embryo growth (Fraxinus, Gingko). Plants that can taste! Seeds of Orobanche, Striga and Alectra are dormant and require a period of afterripening in warm, dry storage, followed by conditioning in a warm, moist environment. Then they will respond to germination stimulants in the soil. Chemcial signal ; non-volatile Î taste Stimulant of Seed Germination Ismene, or Peruvian daffodil or Spider lillies is a monocot genus of lilies with tender perennial bulbs bearing resemblance to Hymenocallis Most seeds need external clues to germinate: for most seeds it is humidity or soil moisture together with with temperatures above 10 C. However there is one exception: the seeds of Ismene or Spider lily that germinate just when they are ready (internal clues). They germinate wherever they might be: in an ashtray a matchbox or in soil. requirements for germination for special seeds Raising orchids from seeds is a gamble few gardeners win. 1903 French botanist Noel Bernard demonstrated that mycorhizal fungi help to provide sugar for the seed germination. 1924 Lewis Knudson (Cornell, US) germinated sterilized orchid seeds on a nutrient gel of agar + sucrose showing that fungus is not obligatory. Orchid protocorms from seeds stem propagation from bulbs or segmenting flower spike s In-vitro germination If the embryo is mature enough (certain size) it can germinate into a complete seedling when freed from the suppression of an impenetrable or authoritarian seed coat. The culture of mature embryos outside the seed coat is used on a large scale in horticulture: it shortens e long dormancy periods of peach, plum, rose, iris seeds. In orchids it is often the only known way to germinate the s How long can seeds live? Lotus seeds or lotus nuts are in the genus Nelumbo, particularly the species Nelumbo nucifera. The seeds are of great importance to East Asian cuisine and are used extensively in traditional Chinese medicine. Brown peel lotus seeds are usually cracked in half in order to remove the germ since the seeds are hard enough to make the germs' removal by needle difficult. Ungerminating Lotus seeds have been found in swamps and could be germinated after 20 000 years of burial. Lupinus, lupines legume family (Fabaceae). In 1954, about 20 seeds were found in prehistoric rodent burrowsin frozen ground near Miller Creek, Yukon. They were 10 000 old. Excitement ensued in 1967, when some of the seeds were successfully germinated. In 1967, they tried to germinate the best-preserved ones... and it worked! A repeat of the carbon dating has confirmed the age of the rodent skull but correct the age of the seeds to 65 years. http://nature.ca/discover/treasures/plnts/tr1/lup_e.cfm How long can seeds live? Date Palm 1963-1965, excavations at Herod the Great's palace on Masada, Israel, revealed a cache of date palm seeds preserved in an ancient jar. They had experienced a very dry and sheltered environment for centuries. Radiocarbon dating at the University of Zurich confirmed the seeds dated from between 155 BC to AD 64. The seeds were held in storage for 40 years at Bar-Ilan University, Jerusalem, until in 2005, In 2005, a preserved 2,000-year-old seed sprouted. It was the oldest known human-assisted germination of a seed. The palm, named Methuselah was about 1.5 m (5 ft) tall as of June 2008. The plant was idientified as the ancient Judean date palm - a cultivar of the date palm (Phoenix dactylifera). http://articles.sfgate.com/2005-06-12/news/17375937_1_judean-date-seedling-ancient-cures Frozen for 32,000 Years, an Arctic Plant Is Revived from seed Living plants have been generated from the fruit of a little arctic flower, the narrow-leafed campion or catchfly Silene stenophylla. that died 32,000 years ago, a team of Russian scientists reports. The fruit was stored by an arctic ground squirrel in its burrow on the tundra of northeastern Siberia and lay permanently frozen until excavated by scientists a few years ago. This would be the oldest plant by far that has ever been grown from seed. The present record is held by a date palm grown from a seed some 2,000 years old that was recovered from the ancient fortress of Masada in Israel. . Dead for 32,000 Years, an Arctic Plant Is Revived by Nicolas Wade in New York Times on February 20, 2012 Svetlana Yashina and David Gilichinsky of the Russian Academy of Sciences research center at Pushchino, appeared in The Proceedings of the National Academy of Sciences of the United States Challenging the future of seeds Seeds germinate when water content exceeds 12 %. Seed starts respiration & exhaust their resources, i.e. they lose the power to germinate (Pharaoh seeds in the pyramids do no longer germinate). Exception is lotus & other seeds with tight seed coat. Ordinary domesticated seeds can be stored for 1-3 years before humidity ruins them. Frits Went tries here to extend life span of seeds with vacuum and chemical drying agents ÎÎ Î Î Life span extended to 20-30 years How long can seeds live? Seed Banking … with the declining $ value this might be a great idea! ... 1. A seed bank is a type of gene bank. A seed bank is a repository of seeds preserved in hermetically-sealed containers at subfreezing temperatures. Seeds that can withstand storage in a seed bank must be desiccation tolerant; therefore species from habitats with seasonal droughts can often be banked while many tropical species can not. 2. Seed Banking refers to populations of seeds in the soil that keep vital for long periods, primarily wild plants. Also many weeds create seed banks, which allow them to germinate at any year and sometimes even long after the mother plant has been eradicated. Seed Banking : Weeds 2. Seed Banking is especially prominent for the success of annuals. Such successful annuals are known as weeds. Most soils contain millions of weed seeds. Researchers in England sifted through the top few inches of soil. In one acre they counted more than ½ million seeds of prostrate knotweed, 700,000 shepherds's purse seeds, 1 1/3 million chickweed seeds, and 6 3/4 million annual bluegrass seeds. For example, a single lambsquarters plant can produce 39,000 seeds in one season. A garden plot in which the lambsquarters would have several million seeds deposited in the seedbank in one year. Redroot pigweed can produce 120,000 seeds in a summer, plantain 36,000, crabgrass 8,000, and mullein 220,000. Seed Banking : e.g. perennial Scotch Broom 2. Seed Banking refers to populations of seeds in the soil that keep vital for long periods Scotch broom , Cytisus scoparius is a deciduous, perennial shrub that grows up to 3m tall & begins to reproduce when approximately three years old and usually lives from 10-15 years. After flowering, it forms black seed pods, carrying an average of 5-9 seeds that disperse after the pods audibly 'pop' open! Scotch broom is known as a 'prolific seed producer' with up to 18,000 seeds per plant which spread by wind, small animals, water and humans. These seeds are protected with a seed coat that can delay germinating for over 30 years. Challenging the future of seeds NORWAY (26 FEBRUARY 2008) - The Svalbard Global Seed Vault opened today on a remote island in the Arctic Circle, receiving inaugural shipments of 100 million seeds ranging from unique varieties of major African and Asian food staples such as maize, rice, wheat, cowpea, and sorghum to European and South American varieties of eggplant, lettuce, barley, and potato. The vault represents the most comprehensive collection of food crop seeds anywhere in the world. Challenging the future of seeds Why is it needed? Who will have access after a catastrophe? Who is in charge? Seeds are a major treasure of our civilization!
