Plants Study Guide Part B Taken from the Plant Structures and Processes informational packet sent home. 1. In mosses and ferns, the plant produces gametes. The female gametes are eggs, and the male gametes are sperm. A layer of water usually from rain or dew must be present for the sperm to be able to swim to the eggs. The result of a sperm uniting with an egg is fertilization. The fertilized egg is called a zygote that develops into a plant which produces spores. When the spores are mature, the spore capsule bursts open and the spores are released and dispersed by the wind. Each individual spore is able to germinate, or sprout, and grow into a plant. 2. With conifers (like pine trees), the tree produces two kinds of cones. The male cones produce spores that develop into pollen grains that get blown by the wind. The female or seed cones produce spores that develop into egg cells in the ovule. The ripening ovule in the female cone secretes a sticky liquid that traps pollen. When pollen grains carried by the wind get stuck in this liquid, pollination occurs (the transfer of male cells to the female cells). The pollen matures into sperm cells. When a sperm cell is carried to the egg cell, the two join and fertilization occurs. The fertilized zygote develops into the plant embryo that becomes the seed. The seeds grow on the scales of the female cone. Scales are types of thick leaves that protect the forming seeds. When the seeds are dispersed by wind or by animals, germination occurs in the right conditions such as proper temperature and amount of water. If conditions are not favorable, the seed may remain dormant until water swells and splits the coat, triggering germination. Seeds develop into seedling roots and begin to grow in the ground. 3. In flowering plants, the flower is the reproductive organ of the plant where seeds are produced. A typical flower is composed of four sets of leaves: sepals, petals, stamens, and carpels. The sepals form the outermost parts of the flower. They are usually green and often thicker than other leaves to protect the young flower while it begins to develop. Within the sepal are the petals which are often brightly colored and scented to attract animal pollinators. 4. Wind or water may serve to pollinate some plants. Many plants rely on insects and other animals to help with pollination. Many types of insects (including bees, ants, butterflies, and moths), birds such as hummingbirds, and even some bats are pollinators. They find food in the flower’s nectar—a sugary substance the plant produces. The animals brush against the anthers containing the male pollen and carry it to the female flower parts. The male reproductive structure called the stamen consists of a thin stalk called the filament with a tip called an anther. The anther produces pollen grains. The female reproductive structure is the pistil. The top of the pistil is called the stigma. The stigma’s surface is sticky in order to capture male pollen grains which develop into sperm cells. The enlarged base of the pistil is the ovary, containing one or more ovules which are individual egg cells that, when fertilized with the sperm cell, develop into seeds. The outermost layer of the ovule becomes the seed coat, and as the ovary around the ovule matures, the ovary is called a fruit. 5. As the ovary or fruit ripens and the seeds form, the other floral parts fall off. The ripened fruit with its seeds may be blown by the wind or water or simply drop to the ground. If an animal eats the fruit, the seeds will pass through the animal’s system and be deposited hours later to grow a new plant. When the temperature and moisture levels are suitable, water softens the seed coat and enters the seed, allowing the embryo to begin to grow. When the embryo splits the seed coat opens, one part grows down in the ground to become the root. Another part grows up to form the shoot, which develops into the stem and leaves. This whole process is called germination. Seed leaves, called cotyledons are the first leaves to emerge from the seed coat. 6. Flowering plants are classified into two groups: monocots and dicots. Monocots have one cotyledon or seed leaf. The total number of flower parts is often a multiple of three. Monocots usually have long narrow leaves with veins running parallel to each other. Grass, grains like wheat, corn, rice, lilies and tulips are examples of monocots. Dicots have two cotyledons, seed leaves. The total number of flower parts on a dicot is often a multiple of four. Dicots tend to have broader leaves with veins that look like nets. Beans, most fruits and vegetables, and many garden flowers are examples of dicots.