Plant Nutrition Quiz 4

The mesophyll cells and the xylem respectively.

The palisade mesophyll and guard cells contain chloroplasts that absorbs sunlight. Most of the chloroplasts are concentrated in the palisade cells.

Most number of chloroplasts is found in the palisade mesophyll layer (2) to ensure maximum absorption of sunlight. Less chloroplasts are found in the spongy mesophyll layer (3). 1 and 4 are epidermal cells which do not contain chloroplasts.

The palisade mesophyll is the main site of photosynthesis.

The palisade mesophyll has the largest number of chloroplasts. The palisade cells are arranged at right angles to the upper epidermis so that more cells can be packed together for maximum absorption of sunlight. The spongy epidermis and guard cells contain fewer chloroplasts.

Structure 1 is an upper epidermis.

Structure 2 is the chloroplast found in the palisade mesophyll cell.

Structure 3 is the xylem.

Structure 4 is the chloroplast found in the spongy mesophyll cell.

Structure 5 is phloem.

Structure 6 is the lower epidermis.

Chlorophyll in chloroplast traps light energy and converts it into chemical energy used in the formation of carbohydrates.

There are two regions of mesophyll-palisade and spongy mesophyll.

Diagram 1 shows an epidermal cell found in the epidermis (structure A) of the transverse section of a leaf in Diagram 2. Region B represents the palisade mesophyll; Region C is a spongy mesophyll and Region D represents the xylem tissue of the vascular bundle in the vein.

Chloroplast carries out photosynthesis for the synthesis of carbohydrates. Chlorophyll in chloroplast traps light energy and converts it into chemical energy used in the formation of carbohydrates.

Layer A is upper epidermis. It does not contain any chloroplast and is unable to carry out photosynthesis.

Layer B is palisade mesophyll cells. It contains chloroplasts to carry out photosynthesis.

Layer C is a spongy mesophyll cells. It contains chloroplast to carry out photosynthesis.

Layer D is the lower epidermis with guard cell. The guard cells contain chloroplast to carry out photosynthesis.

Between points X and Y, increasing light intensity no longer increases the rate of photosynthesis. This shows that light intensity is no longer the limiting factor (i.e. directly controlling the rate of photosynthesis). Other factors, carbon dioxide and temperature, are now the limiting factors.