Figure 10.4: Stomata are pores in leaves that allow gasses to pass through, but they can be
closed to conserve water. ( 1 )
tissue is not necessary since the entire body is in contact with the water. But on land, water
may only be present deep in the ground. Vascular tissue delivers water and nutrients from
the ground up and food down into the rest of the plant. The two vascular tissues are xylem
and phloem. Xylemis responsible for the transport of water and mineral nutrients from
the roots throughout the plant. It is also used to replace water lost during transpiration and
photosynthesis.Phloemmainly carries the sugars made during photosynthesis to the parts
of the plant where it is needed.
Plant Reproduction and Life Cycle
Alteration of generations describes the lifecycle of a plant (Figure10.5). In alternation of
generations, the plant alternates between asporophytethat has two sets of chromosomes
(diploid)andagametophytethathasonesetofchromosomes(haploid). Briefly,alternation
of generations can be summarized in the following four steps: follow along inFigure10.5
as you read through the steps.
- The gametophyte produces the gametes, sperm and egg, by mitosis. Remember,
gametes are haploid. - Then the sperm fertilizes the egg, producing a diploid zygote that develops into the
sporophyte. - The sporophyte produces haploid spores by meiosis.
- The haploid spores undergo mitosis, developing into the gametophyte.