SparkNotes: Essential Processes of Plants: Introduction and Summary - Homework Help

SparkNotes: Essential Processes of Plants

Introduction and Summary
Plants carry out a number of processes that are essential to their survival. Internal water and sugar transport are largely carried out within the vascular system. The upward flow of water through the xylem is "pulled" by transpiration, while the flow of organic nutrients (sugars) through the phloem is "pushed" by turgor pressure from sources to sinks. These processes ensure that the entire plant receives water and food even though these materials are brought in or produced only in certain parts of the plant-- the roots and leaves, respectively.

Plant hormones determine the timing and occurrence of many of the processes of the plant, from germination to tissue growth to reproduction. These hormones are divided into five classes, each with its own function within the plant. The classes are composed of auxins, cytokinins, gibberellins, inhibitors, and ethylene. Auxins play a role in phototropism, the growth of a plant toward a light source. This growth, described by the acid growth hypothesis, results from the rapid elongation of cells on the dark side of the plant.

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