Water diffuses into a plant through its root hairs and then travels into the parenchymal cells of the cortex along the symplast and the apoplast. Then the water moves to the endodermis where it freely passes into the vascular cylinder and into the xylem. Once the water is in the xylem it moves upward toward the leaves. Then the water diffuses from the roots where the water potential is the highest to the air spaces in the leaves where the water potential is the lowest. From the veins in the leaf the water diffuses into air spaces within the sponge mesophyll and then into the palisade and spongy mesophyll cells as needed for photosynthesis. In the light reactions of photosynthesis the water molecules are broken during photosynthesis. The oxygen from the water molecules are given off as a waste product.
Plant life began in the seas and then they started to move to the land as competition for resources increased. Problems faced by land plants were support of the plant body, absorbing and conserving water, and reproducing outside of a water environment. The most common type of plant tissue is ground tissue which functions to support the plant. Roots help with anchoring the plant into the soil and also absorb nutrients. Root hairs greatly increase the the surface area’s absorption. The opening and closing of the stomata limits the loss of water by transpiration and are controlled by guard cells. A waxy cuticle made of cutin covers leaves which minimize the loss of water further. Some plants have evolved in dry envioronments that has allowed for their minimal loss of water such as C-4 plants that differ from C-3 planst in leaf anatomy. C-4 plants have bundle sheath cells that lie deep within the leaf wraped around the veins sequestering the CO2 away from the somatas. Reproduction is made possible with some plants that have their gametes and zygotes formed within a protective jacket of cells called gametangia that prevents drying out. Sporopollenin found in...
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