1 Vegetative Plant Development Chapter 36

2 Angiosperm Embryo Development

3 Establishing Three Tissue Systems Protoderm will become dermal tissue – protects plant from desiccation Ground meristem will form ground tissue – function in food and water storage Procambium will form vascular tissue – perform water and nutrient transport

4 Establishing Three Tissue Systems Root and shoot formation – established during globular stage of development  formation of each controlled independently Morphogenesis – globular stage gives rise to heart-shaped embryo with cotyledons produced by embryonic cells

5 Establishing Three Tissue Systems Food storage – starch, lipids, and proteins produced throughout embryogenesis  sporophyte transfers nutrients via suspensor in angiosperms

6 How Seeds Form Protective seed coat forms from outer layers of ovule cells – embryo either surrounded by nutritive tissues, or amassed food in cotyledons – seed resistant to drought and other unfavorable conditions  vehicle for dispersal

7 How Seeds Form Adaptive importance of seeds – maintain dormancy until better conditions arise – afford maximum protection to young plant at most vulnerable developmental stage – contain adequate food supply until photosynthetic food supply available – adapted for dispersal

8 How Seeds Form Specific germination triggers – exposure to heat or fire – leaching inhibitory chemicals from seed coats – passage through animal intestines

9 How Fruits Form Fruits are mature ovaries.

10 How Fruits Form Dispersal of fruits – vertebrate digestive tracts  bright colors – animal coats  hooked spines – wind  wings – water  buoyant

11 Mechanisms of Germination Germination begins when a seed absorbs water and resumes metabolism. – may fail to germinate without additional environmental signals  stratified - held at low temperatures

12 Mechanisms of Germination Utilization of reserves – Germination and early seedling growth require the utilization of metabolic reserves stored in starch grains of amyloplasts.  cereal cotyledons modified into scutellum – mediated by gibberellic acid and abscisic acid

13 Summary Establishing the Root-Shoot Axis Establishing Three Tissue Systems How Seeds Form How Fruits Form Mechanisms of Germination

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