BIO 201 Lecture Notes - Lecture 21: Double Fertilization, Flowering Plant, Phloem
18 Apr 2017
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Bio 201 lecture 21: plant transport (water & food) Most angiosperms rely on animals (insects, birds, and bats) to transfer pollen. Seeds (baby plant with food endosperm) within the fruit is dispersed by animals as well. But some plants have other mechanisms for seed dispersal. Goal: understand the processes by which water and solutes are transported through the xylem and phloem. 2 models of transport in plants: (1) transpiration-cohesion-tension (tct) model: Explains how water is transported through plant xylem. (2) pressure flow model: Explains how food is translocated in the phloem. Observation: it takes energy to change water from liquid to vapor. In a study in phoenix, arizona, the surface temperature of asphalt measured 140 f on a hot summer day, while a nearby patch of shaded grass measured 104 f (mueller and day 2005). Leaf and stem epidermis has a waxy cuticle to minimize water loss, but it also prevents gas exchange.
