Ch 9: Plant Nutrition and Gas Exchange

Flashcards covering plant nutrition and gas exchange.

Autotroph

An organism that can produce its own food using light, water, carbon dioxide, or other chemicals.

Photosynthesis

The process by which plants use sunlight, water, and carbon dioxide to create their own food and release oxygen.

Nitrogen (in plants)

Essential for the synthesis of amino acids, proteins, nucleic acids, and chlorophyll. Deficiency leads to poor growth and yellow leaves (chlorosis).

Phosphorus (in plants)

Essential for the synthesis of cell membranes, ATP, and nucleic acids. Deficiency leads to poor growth and purple leaves.

Potassium (in plants)

Required in some enzymatic reactions, promotes photosynthesis and transport. Deficiency leads to poor growth and blackened leaf edges.

Magnesium (in plants)

Required in some enzymatic reactions and essential for the synthesis of chlorophyll. Deficiency leads to poor growth and yellow leaves (chlorosis).

Gas exchange in terrestrial plant leaves

Gases from the environment diffuse into the air space through the stoma, dissolve in the water film on the surfaces of mesophyll cells, and diffuse into the cells. Gases produced by the cells follow the reverse path to exit.

Gas Exchange in Plants

In terrestrial plants, gas exchange occurs through stomata on leaves and herbaceous stems, lenticels on woody stems, and the surface of roots. Submerged leaves exchange gas over the leaf surface. Floating leaves exchange gas through stomata in the upper epidermis.

Adaptations of Leaves for Gas Exchange

Includes broad, flat leaves for large surface area, thin leaves for short diffusion distance, loosely packed spongy mesophyll cells with numerous air spaces for free diffusion, a water film on mesophyll cells for gas dissolution, and stomata with guard cells for regulating gas exchange.

Light Intensity and Gas Exchange - No Light

Only respiration occurs, leading to a net uptake of oxygen and a net release of carbon dioxide.

Light Intensity and Gas Exchange - Low Light Intensity

The rate of photosynthesis is lower than the rate of respiration, leading to a net uptake of oxygen and a net release of carbon dioxide.

Light Intensity and Gas Exchange - At Compensation Point

The rate of photosynthesis equals the rate of respiration, resulting in no net gas exchange.

Light Intensity and Gas Exchange - High Light Intensity

The rate of photosynthesis is higher than the rate of respiration, leading to a net uptake of carbon dioxide and a net release of oxygen.