James Karl G. Honrado
9 – Marangal
1. The role of photosynthesis and amino acid metabolism in the
energy status during seed development
Seeds are the major organs responsible for the evolutionary upkeep of angiosperm
plants. Seeds accumulate significant amounts of storage compounds used as nutrients
and energy reserves during the initial stages of seed germination. The accumulation of
storage compounds requires significant amounts of energy, the generation of which can
be limited due to reduced penetration of oxygen and light particularly into the inner parts
of seeds. In this review, we discuss the adjustment of seed metabolism to limited
energy production resulting from the suboptimal penetration of oxygen into the seed
tissues. We also discuss the role of photosynthesis during seed development and its
contribution to the energy status of developing seeds. Finally, we describe the
contribution of amino acid metabolism to the seed energy status, focusing on the Aspfamily pathway that leads to the synthesis and catabolism of Lys, Thr, Met, and Ile.
Published online: June 27, 2014
Citation: Galili G, Avin-Wittenberg T, Angelovici R and Fernie AR (2014) The role of
photosynthesis and amino acid metabolism in the energy status during seed
development. Front. Plant Sci. 5:447. doi: 10.3389/fpls.2014.00447
2. - The evolution of photosynthesis refers to the origin and subsequent evolution
of photosynthesis, the process by which light energy from the sun is used to
synthesize sugars from carbon dioxide, releasing oxygen as a waste product.
The first photosynthetic organisms probably evolved early in the evolutionary history of
life and most likely used reducing agents such as hydrogen or hydrogen sulfide as
sources of electrons, rather than water.[1] There are three major metabolic pathways by
which photosynthesis is carried out: C3 photosynthesis, C4 photosynthesis, and CAM
photosynthesis. C3photosynthesis is the oldest and most common form.
Chemical Reactions:
-6CO2 + 6H2O (+ light energy) → C6H12O6 + 6O2.
This is the source of the O2 we breathe, and thus, a significant factor in the concerns
about deforestation.
-The light reaction happens in the thylakoid membrane and converts light energy to
chemical energy. This chemical reaction must, therefore, take place in the light.
Chlorophyll and several other pigments such as beta-carotene are organized in clusters
in the thylakoid membrane and are involved in the light reaction. Each of these
differently-colored pigments can absorb a slightly different color of light and pass its
energy to the central chlorphyll molecule to do photosynthesis. The central part of the
chemical structure of a chlorophyll molecule is a porphyrin ring, which consists of several
fused rings of carbon and nitrogen with a magnesium ion in the center.
-The dark reaction takes place in the stroma within the chloroplast, and converts CO2 to
sugar. This reaction doesn’t directly need light in order to occur, but it does need the
products of the light reaction (ATP and another chemical called NADPH). The dark
reaction involves a cycle called the Calvin cycle in which CO2 and energy from ATP are
used to form sugar. Actually, notice that the first product of photosynthesis is a threecarbon compound called glyceraldehyde 3-phosphate. Almost immediately, two of these
join to form a glucose molecule.
3. Research Question: Are there other advantages of light in photosynthesis process
and can it affect the metabolic pathway of plants?
4. All plants possess adaptations to cope with stresses imposed by the environment in
which they exist. Allometric relationships in plant growth form, the adaptive significance
of resprouting, germination strategies and benefits of dispersal in space and time,
thresholds for survival to varying light, temperature and energy environments,
responses of individual species and community wide phenomena to changing CO2
levels and increasingly dry conditions associated with changing global climate.
5. Bacterial Photosynthesis
-Bacterial photosynthesis is a light-dependent, anaerobic mode of metabolism. Carbon
dioxide is reduced to glucose, which is used for both biosynthesis and energy
production. Depending on the hydrogen source used to reduce CO2, both
photolithotrophic and photoorganotrophic reactions exist in bacteria.
Sources:
http://journal.frontiersin.org/Journal/10.3389/fpls.2014.00447/abstract
http://en.wikipedia.org/wiki/Evolution_of_photosynthesis
http://www.jcu.edu.au/mtb/research/projects/JCUDEV_018382.html
http://www.ncbi.nlm.nih.gov/books/NBK7919/