BIOL 2300 Lecture Notes - Lecture 6: Mulch, Stoma, Allan Savory
22 Jun 2018
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LECTURE 6 PLANTS AND ENVIRONMENTAL CHANGE
Plant Adaptations to Environmental Variability
• Plants have evolved a variety of adaptations to successfully grow, reproduce
and survive across the entire range of environmental conditions on Earth.
Plants: Introduction
Photosynthesis
• Process where energy from the sun is used to transform CO2 into
carbohydrates (simple sugars) and O2
• Photosynthesis takes place in specialized cells (mesophyll cells) in the leaf
• Chlorophyll (light absorbing pigment) traps light energy → synthesizes ATP
→ this energy drives CO2 → O2 + sugars
• This chemical reaction is dependent on enzyme called rubisco.
2
Respiration
• In the mitochondria of cells (plant & animal) – carbohydrates are broken down
to generate energy (ATP), releasing CO2
• Plants both use and produce CO2 and the difference in the rates of these two
processes is:
o Net Photosynthesis = Photosynthesis – Respiration
= carbon uptake – carbon loss
Diffusion
• Movement of a substance from areas of higher to lower concentration
• CO2 diffuses into the leaf through openings in the surface of the leaf, called
stomata
• As CO2 diffuses into the leaf, water diffuses out of the leaf.
o Transpiration
o CO2 enters: atmosphere > leaf
o Water leaves: atmosphere < leaf
• Water lost must be replaced with water taken by roots from the soil.
Plants must acquire essential resources: light, CO2, water,
nutrients
• Leaf tissue – photosynthesis (uptake of CO2)
• Stem tissue – structural support (gain access to light)
• Root tissue – water and nutrient uptake from the soil
Individual Responses of Plants
• Plants adapt to different environmental conditions to keep:
o Photosynthesis > Respiration (+ carbon balance → grow)
o Photosynthesis > Transpiration (+ water balance → survive)
Document Summary
Plant adaptations to environmental variability: plants have evolved a variety of adaptations to successfully grow, reproduce and survive across the entire range of environmental conditions on earth. Plants must acquire essential resources: light, co2, water, nutrients: leaf tissue photosynthesis (uptake of co2, stem tissue structural support (gain access to light, root tissue water and nutrient uptake from the soil. Individual responses of plants: plants adapt to different environmental conditions to keep, photosynthesis > respiration (+ carbon balance (cid:314) grow, photosynthesis > transpiration (+ water balance (cid:314) survive) Individuals can balance leaf vs root tissue: increase the photosynthetic surface (maximizes co2 uptake and photosynthetic rates (cid:314) growth, no increase in other tissues (i. e. shoot, root) because this increases the rate of respiration (co2 loss) Plants light conditions: plants are either adapted to low light (shade-tolerant) or high light (shade- intolerant, species adaptation.
