Lecture 14: Gas Exchange in Plants Flashcards
(27 cards)
Why do organisms need to exchange materials between their cells and the environments? what is the role of diffusion in this process?
Organisms must conduct gas exchange with their environments in order to perform the necessary metabolic functions for life (photosynthesis and cellular respiration).
Diffusion allows for gas exchange between cells and their environments.
What is the relationship between the size of an organism, its surface area and the ability of its cells to exchange materials with its environment?
The smaller the size of the organism, the larger the SA will be in relation to its body size, so more cells will be exposed to the environment and more diffusion can occur.
Define gas exchange
the process of plants taking up the gases they need for metabolic processes (CO2, H2O and O2)
and the process of releasing waste gases by exchange
Define cellular respiration
A metabolic process that requires the intake of O2 to create ATP and waste products: CO2 and H2O.
What is the relationship between gas exchange and cellular respiration in organisms?
it is complementary, the waste products of one are the reactants of the other.
How are photosynthesis and cellular respiration complementary metabolic processes?
- CO2 and H2O are reactions for photosynthesis
- Photosynthesis produces organic molecules (sugar), and O2 as a waste product.
- O2 is used as a reactant for CR
- CR produces ATP, and CO2 and H2O as waste products
- CO2 and H2O are used as reactants for photosynthesis
Describe root hairs and how they function in gas exchange
root hairs are thin, hair-like, branching projections that grow off of plant roots to increase the plant’s surface area (and therefore gas exchange abilities). In good soils, there are air pockets with which root hairs and roots can exchange gases (O2) for cellular respiration.
Describe Lenticels and how they function in gas exchange
lenticels are located on the bark of woody-stemmed plants (ex. tree trunk surface) and allow for the gas exchange in living cells of phloem tissues.
similar to stomata but are always open and only in woody plants.
Describe stomata and how they function in gas exchange
stomata are located on the surface of the plant stems/leaves to regulate the passage of gases into and out of the leaves and green stems of plants.
Stomata open and close for gas exchange in order for the molecules to bypass the waxy cuticle that prevents molecules from moving in and out of the surface.
stomata are controlled by the guard cells of the dermal tissue system.
Describe the structure and function of a stoma and how it is able to open and close
- Stomata are pores in the stem/leaf surface that are flanked by 2 specialized cells (guard cells).
- guard cells change shape when water moves into or out of them and cause a stoma to open or close
What triggers a stoma to open?
water entering the guard cells will make them turgid and open the stoma
What triggers a stoma to close?
water leaving the guard cells will make them flaccid and close the stoma
T or F: if a stoma is open, the guard cells are turgid. Why/why not?
True. the cells are highly specialized and when water enters the guard cells they become turgid/pressurized and bow out to open.
T or F: if a stoma is closed, the guard cells are flaccid. Why/why not?
TRUE. When water exits the guard cells, they will become flaccid and not have the support to stay open and droop closed.
How does the structure of a leaf facilitate gas exchange? What are the 3 structures involved in gas exchange?
Plant leaves maximize surface area to facilitate gas exchange by having many air spaces to allow for contact between air and cells.
air spaces allow gas exchange to occur in parts of leaves that are not in direct contact with the atmosphere.
- palisade mesophyll tissues
- spongy mesophyll tissues
- stomata
T or F: gases are transported long distances in plants? why/why not?
FALSE. All living cells must conduct gas exchange.
environmental conditions that will trigger a stoma to close?
- drought/dry soil
- high temperature (evapotranspiration is higher)
- lack of light
environmental conditions that will trigger a stoma to open?
- moisture
- low temperatures
- light –> photosynthesis requires gas exchange (must be open)
- [CO2] too low or [O2] too high inside leaf
What are the two mesophyll tissues in plant leaves that function in gas exchange? describe them
- palisade mesophyll tissue:
- composed of PARENCHYMA cells
- chloroplasts concentrated tightly at the leaf surface for photosynthesis (and gas exchange) - spongy mesophyll tissue:
- composed of PARENCHYMA cells
- looser packed with more air pores
- sponginess allows the air to move around the leaf to allow for more gas exchange across cell surfaces as these tissues are deeper in the leaf structure and are not exposed to the environment – air pores allow for gas exchange within the leaf.
What are the two mesophyll tissues in plant leaves that function in gas exchange? describe them
- palisade mesophyll tissue:
- composed of PARENCHYMA cells
- chloroplasts concentrated tightly at the leaf surface for photosynthesis (and gas exchange) - spongy mesophyll tissue:
- composed of PARENCHYMA cells
- looser packed with more air pores
- sponginess allows the air to move around the leaf to allow for more gas exchange across cell surfaces as these tissues are deeper in the leaf structure and are not exposed to the environment – air pores allow for gas exchange within the leaf.
How do veins/vascular bundles function in plant leaves?
- made up of xylem and phloem tissues
- carry materials across distances of the plants
How do veins/vascular bundles function in plant leaves?
- made up of xylem and phloem tissues
- carry materials across distances of the plants
- every part of the leaf has veins in contact with it bc those are the vascular tissues that bring necessities for all cell life.
How does gas exchange occur in the living cells of the woody stems, branches, and roots of trees?
Gas exchange occurs everywhere
but, in woody plants, xylem cells are in the middle of the tree trunk and are dead at maturity so don’t require gas exchange
phloem cells are alive but are only on the surface so they can perform gas exchange.
How does gas exchange occur in the living cells of the woody stems, branches, and roots of trees?
Gas exchange occurs everywhere
but, in woody plants, xylem cells are in the middle of the tree trunk and are dead at maturity so don’t require gas exchange
phloem cells are alive but are only on the surface so they can perform gas exchange.
