Under stressful conditions, abscisic acid can cause guard cells to give up potassium ions and close stomata. Carbohydrates are stored as starch in most plants. Sucrose is the main form in which sugars are transported through most plants. Describe the role of sieve tube members and companion cells in translocation. According to the pressure flow theory, pressure builds up at the source end of a sieve tube system and pushes solutes toward a sink, where they are removed.
Companion cells supply the energy that loads sucrose at the source.
Sexual reproduction requires formation of gametes, followed by fertilization. The production of individuals in clones describes asexual reproduction. Give the relationship of a flower to a sporophyte. Distinguish between sporophytes and gametophytes. Sporophytes have several means of reproducing themselves asexually.