Unit 5 vegetation_lecture 2

Unit 5 vegetation_lecture 2 - Unit 5: Vegetation Lecture 2...

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1 Unit 5: Vegetation Lecture 2 Plant Adaptations Adaptations to Flooding • Tolerance vs. Avoidance – Tolerance adaptations which minimize sensitivity to or alleviate plant from adverse effects of flooding (ten to be short-term solutions) – Avoidance adaptations which elevate adverse effects of flooding (tend to be long-term strategies to deal with adverse effects of flooding) • Physiological vs. Morphological – Physiological adaptations relate to chemical or metabolic changes in the plant. – Morphological adaptations related to physical or structural changes in the plant Metabolic Adaptation regulation of alcohol dehydrogenase • Non-induction – Non-induction or inhibition of ADH reduces conversion of acetaldehyde to ethanol. –P ro s • Causes acetaldehyde and pyruvate to buildup slowing fermentation. • Lower rate of fermentation reduces toxic effects of ethanol as and conserves carbohydrate reserves prolonging sources of stored energy. – Con’s • Lower immediate energy availability • Increase in acetaldehyde
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2 • Induction of ADH – Increased rate of glycolysis to make up for lower energy conversion efficiency under anaerobic fermentation –P ro s • Get as much energy in short term as possible • Reduces concentration of acetaldehyde in tissue – Con’s • Ethanol, builds up, but is highly soluble in water • Rapidly consumes energy reserves from plant and metabolic byproducts are lost to environment and can’t be recovered. Metabolic Adaptation regulation of alcohol dehydrogenase Metabolic Adaptations Alternative end products of Fermentation Accumulation of malic and other fatty acids has been observed in wetland plants. Speculation that wetland adapted plants lack or suppress malic enzyme allowing malate to form. This is a low toxicity compound that can accumulate and is not converted to acetaldehyde and ethanol. Upon reoxidation, malate can be used as carbon source to recover remaining energy stores. Morphological Adaptations • Lenticels • Adventitious Roots • Pneumatophores • Prop Roots • Rhizome and Starch Storage • Stem Elongation • Hypertrophied Stem • Aerenchyma
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3 Lenticels Lenticels Pores that form between the atmosphere and the cambium layer of stems and trunks Triggered by ethylene production Only occur on woody species Increase gas transfer to the cambium Have greatest concentration near the air water interface Have been shown to influence O 2 concentration in Red Mangrove prop roots by 90% if blocked. O 2 O 2 O 2 O 2 O 2 O 2 Lenticels Phloem Cortex Xylem Outer Bark Lenticels Lenticels [Tupelo seedlings] CO 2 CH 4 Adventitious Roots • Triggered by increase in ethylene • Form in zone of minimal oxygen stress – Stagnant water at surface – Flowing water throughout water column • Varying between species • Can develop within days of inundation
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Unit 5 vegetation_lecture 2 - Unit 5: Vegetation Lecture 2...

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