Plant Adaptions Flashcards
Light dependent reactions
chlorophyll absorbs light energy and sets off an electron transport chain that results in the production of ATP (“molecular currency”) and NADPH
Aerobic and Anaerobic Cellular Respiration
Light independent (Dark) reactions
enzymatic driven reaction that utilizes ATP and NADPH to make sugars, and regenerate enzyme Rubisco that drives the Calvin Benson Cycle
Epidermis
Outer Layer
Chlorophyll
light absorbing pigment
chloroplast
organelles that conduct photosynthesis
stoma
pores in the epidermis that allow gas exchange
mesophyll
where photosynthesis primarily occurs
vascular bundle
transport of water and nutrients
Water Use Efficiency
tradeoff between water kept in leaf versus CO2 that can get into the leaf; ratio of net primary production to transpiration of water by a plant
C3
any plant that produces the 3 carbon compound PHOSPHOGLYCERIC ACID in its first step during photosynthesis:Advantage- light and dark reactions take place in same cell(does not require additional energy to shuttle initial 3C to other cells,Disadvantage- loses more water than C4 and CAM
:C4
any plant that produces the 4 carbon compound MALIC/ASPARTIC ACID in its first step during photosynthesis:spatioal separation of light dependent(mesophyll) and independent reactions(bundle sheath),Advantage- more water use efficient than C3,Disadvantage- more costly, needs additional ATP
CAM Pathways
CO2 incorporated into 4 carbon organic acids(carbon fixation)->organic acids release CO2 to Calvin Cycle. In CAM plants, carbon fixation and the calvin cycle occur in the same cells at different times
Carbon Allocation
strategy of carbon investment into leaves, roots, stems, secondary chemical compounds
Shade Tolerance
plants ability to grow and survie in low light
aerobic and anaerobic cellular respiration
Carbon Balance
balance between uptake of CO2 and loss through repiration.positive-more CO2 than out(plant is ok)
negative- more respiration than photosynthesis (not good for plant). Affected by light temperature and water
Light Compensation Point
level of PAR where carbon balance is not + or -
Light Saturation Point
maximum rate of photosynthesis
Heterotroph
organisms that are unable to manufacture their own food from inorganic materials and thus rely on other organisms, living and dead, as a source of energy and nutrients
autotroph
organisms that produce organic material from inorganic chemicals and some source of energy
photosynthesis
use of light energy by plants to convert carbon dioxide and water into simple sugars
bundle sheath cells
cells surrounding small vascular bundles in the leaves of vascular plants
transpiration
loss of water vapor from a plant to the outside atmosphere
Rubisco
enzyme in photosynthesis that catalyzes the initial transformation of into sugar
net photosynthesis
difference betweeen the rate of carbon uptake in photosynthesis and carbon loss in respiration
temperature effects on photosynthesis
The opening of stomata’s benefits and costs for plants in dry environments.
Advantage- In dry environments, plants keep their stomata closed to limit water loss yet they must open their stomata to exchange gases with the environment. In dry environments, there is a also a physical increase in evaporation. Plants heat up faster and need to open their stomata to cool off.Disadvantage- the drier the air, the more rapidly the water insde the leaf will diffuse through the stomata into the outside surrounding air, it it does not replace the water lost it will wilt and die. C4 and CAM photosynthesis are both adaptations to arid conditions because they result in better water use efficiency. In addition, CAM plants can “idle,” saving precious energy and water during harsh times, and C4 plants can photosynthesize faster under the desert’s high heat and light conditions than C3 plants because they use an extra biochemical pathway and special anatomy to reduce photorespiration.
Describe the features of C3, C4 and CAM photosynthetic strategies.
C3 plants.
Called C3 because the CO2 is first incorporated into a 3-carbon compound.
Stomata are open during the day.
RUBISCO, the enzyme involved in photosynthesis, is also the enzyme involved in the uptake of CO2.
Photosynthesis takes place throughout the leaf.
Adaptive Value: more efficient than C4 and CAM plants under cool and moist conditions and under normal light because requires less machinery (fewer enzymes and no specialized anatomy)..
Most plants are C3.
C4
Called C4 because the CO2 is first incorporated into a 4-carbon compound.
Stomata are open during the day.
Uses PEP Carboxylase for the enzyme involved in the uptake of CO2. This enzyme allows CO2 to be taken into the plant very quickly, and then it “delivers” the CO2 directly to RUBISCO for photsynthesis.
Photosynthesis takes place in inner cells (requires special anatomy called Kranz Anatomy)
Adaptive Value:
Photosynthesizes faster than C3 plants under high light intensity and high temperatures because the CO2 is delivered directly to RUBISCO, not allowing it to grab oxygen and undergo photorespiration.
Has better Water Use Efficiency because PEP Carboxylase brings in CO2 faster and so does not need to keep stomata open as much (less water lost by transpiration) for the same amount of CO2 gain for photosynthesis.
C4 plants include several thousand species in at least 19 plant families. Example: fourwing saltbush pictured here, corn, and many of our summer annual plants.
CAM
CAM stands for Crassulacean Acid Metabolism
Called CAM after the plant family in which it was first found (Crassulaceae) and because the CO2 is stored in the form of an acid before use in photosynthesis.
Stomata open at night (when evaporation rates are usually lower) and are usually closed during the day. The CO2 is converted to an acid and stored during the night. During the day, the acid is broken down and the CO2 is released to RUBISCO for photosynthesis
Adaptive Value:
Better Water Use Efficiency than C3 plants under arid conditions due to opening stomata at night when transpiration rates are lower (no sunlight, lower temperatures, lower wind speeds, etc.).
May CAM-idle. When conditions are extremely arid, CAM plants can just leave their stomata closed night and day. Oxygen given off in photosynthesis is used for respiration and CO2 given off in respiration is used for photosynthesis. This is a little like a perpetual energy machine, but there are costs associated with running the machinery for respiration and photosynthesis so the plant cannot CAM-idle forever. But CAM-idling does allow the plant to survive dry spells, and it allows the plant to recover very quickly when water is available again (unlike plants that drop their leaves and twigs and go dormant during dry spells).
CAM plants include many succulents such as cactuses and agaves and also some orchids and bromeliads
cross section of a C3 plant leaf
PAR for a shade tolerant and a shade intolerant plant
