L1- Plant Response to light (Photosynthesis)

Crop Physiology CRSCI 3300

Cuticle

A waxy, waterproof layer on the top of the leaf that prevents water loss.

Epidermis

The protective outer layer of cells on the top (upper epidermis) and bottom (lower epidermis) of the leaf.

Palisade Mesophyll

A layer of elongated cells located under the upper epidermis. These cells are rich in chloroplasts and are the main site of photosynthesis.

Spongy Mesophyll

A layer of irregularly shaped cells with large air spaces, located below the palisade layer. These air spaces facilitate gas exchange.

Stomata

Tiny pores, mostly found in the lower epidermis, that allow for the exchange of gases (CO2, O2 , water vapor)

Veins

Vascular bundles within the leaf that contain xylem (for water transport) and phloem (for sugar transport).

Light-Dependent Reactions

This stage occurs within the thylakoids and grana. The thylakoid membranes contain pigments like chlorophyll that absorb sunlight. This light energy is used to split water molecules (H2​O), releasing oxygen (O2​) as a byproduct and creating energy-storing molecules (ATP and NADPH).

Light-Independent Reactions (Calvin Cycle)

This stage takes place in the stroma, the fluid-filled space surrounding the thylakoids. The ATP and NADPH produced in the first stage are used to convert carbon dioxide (CO2​) from the air into glucose (sugar).