BSC 196 Lecture Notes - Lecture 23: Active Transport, Transpiration, Protoplast
Document Summary
Xylem transports water and minerals from roots to shoots. Phloem transports photosynthetic products from sources to sinks. Stems are conduits for water and nutrients and supporting structures for leaves. Shoot length and branching pattern affect light capture. Phyllotaxy: arrangement of leaves on a stem; species-specific trait important for light capture. Most angiosperms: alternate phyllotaxy ; leaves form a spiral. The depth of the canopy, the leafy portion of all the plants in a community, affects the productivity of each plant. Self-pruning, the shedding of lower shaded leaves, occurs when they respire more than photosynthesize. In low-light conditions, horizontal leaves capture more sunlight. In sunny conditions, vertical leaves are less damaged by sun and allow light to reach lower leaves. Roots and the hyphae of soil fungi form mutualistic associations called mycorrhizae. Mycorrhizal fungi increase the surface area for absorbing water and minerals, especially phosphate. The apoplast consists of everything external to the plasma membrane.
