Chapter36PlantFormandFunction[1] - BLY 122 Chapter 36 Plant...

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1 BLY 122 Amy Hunter from C. S. Major Chapter 36 Plant form and Function I. The Diversity of Plant Form A. Plants need light, carbon dioxide, water, nitrogen, phosphorus, magnesium, and potassium to photosynthesize make macromolecules, and maintain their structure. (Fig 36.1) B. Plants use two basic systems to acquire these resources. 1. The root system (a vertical taproot with lateral roots that branch horizontally) is belowground and acquires water and dissolved nutrients from soil. ( Fig. 36.2 ) 2. The shoot system is aboveground and acquires the carbon dioxide and light from the atmosphere. ( Fig. 36.3 ) a. The shoot system consists of stems with nodes where leaves are attached. b. Internodes are stem segments between leaves. c. Lateral buds grow at nodes and can develop into branches or leaves. d. Apical buds grow at the tip of the main stem. 3. The vascular tissue connects the root and shoot systems by transporting water and nutrients from the roots to the shoots and by transporting glucose and other nutrients from leaves to the rest of the plant. II. The Diversity of Root Systems: North American Prairie Plants A. Experiment: Trenches were cut exposing the roots of various plant species in Kansas prairie, and J. E. Weaver examined the extent and nature of the root systems. B. Observations 1. Roots of different species grew to different depths. ( Fig. 36.4 ) 2. Morphology of different root systems was variable; some taproots, some fibrous, some large storage roots. C. Interpretation: Root system diversity enables many species to live together in the same environment without directly competing for the same resources. ( Fig. 36.4 ) 1. Grasses have dense, fibrous root systems. 2. Prairie roses have extremely long taproots. 3. Other plants have thick roots that store starch. D. All roots function to provide support and nutrient and water absorption. E. Adventitious roots are lateral roots that develop out of shoots. (Example, mangrove swamps) F. Roots show a great deal of phenotypic plasticity i.e., they are plastic or changeable depending on environmental conditions III. Diversity in Shoot Systems A. The shoot system consists of one or more stems which are vertical aboveground structures Nodes: sites of leaf attachment Internodes: segments between nodes Leaf: a leaf is an appendage that projects from a stem laterally Axillary Buds: site of node attachment to stem—may develop into a branch if conditions are appropriate. B. Diversity in shoots analyzed on three levels: Morphological Diversity among species Phenotypic Plasticity within individuals Modified Shoots with specialized functions Example of morphological diversity: Silverswords are a monophyletic group of plants that are variable in growth form, size, shape, and habitat. 1.
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Chapter36PlantFormandFunction[1] - BLY 122 Chapter 36 Plant...

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