Botany and Plant Science

The parenchyma cells in the phloem tissue are known as phloem parenchyma. There are different types of phloem parenchyma cells, companion cells, albuminous and other parenchyma cells. The transfer cells are a type of companion cells. These are the cells which have folded cell wall surface. This helps to increase the transfer of the sugar in the lateral sides. They also help in scavenging the solutes which require ATP to move across the membranes. 

Palisade parenchyma cells are plant cells found within the mesophyll in leaves, right below the upper epidermis and cuticle. They are vertically elongated, a different shape from spongy mesophyll cells beneath them in the leaf. Their chloroplasts absorb a major portion of the light energy used by the leaf. 

Palisade cells are plant cells found within the mesophyll in leaves, right below the upper epidermis and cuticle. They are vertically elongated, a different shape from spongy mesophyll cells beneath them in the leaf. Their chloroplasts absorb a major portion of the light energy used by the leaf. Palisade cells occur in dicotyledonous plants and also in the net-veined monocots. The spongy mesophyll are usually ball-shaped with large intercellular spaces but usually contains fewer chloroplasts than the palisade cells. They are also present in dicot leaf. 

Dorsiventral leaf i.e. Mesophyll is the ground tissue and it occurs between the two epidermal layers. It is heavily composed of chlorenchyma cells. The mesophyll is differentiated into two regions an upper palisade parenchyma and lower spongy parenchyma. Palisade parenchyma is again composed of two or three layers of elongated and compactly arranged chlorenchyma cells.

Also, the isobilateral leaf has undifferentiated mesophyll.

Therefore, the correct answer is option B.

Leaves, in which both surfaces are differentiated are called dorsiventral leaves. In these leaves, palisade parenchyma is present towards the upper epidermis and spongy parenchyma is present towards the lower epidermis. Because of this reason, in dorsiventral leaves, the upper side is dark green in colour and lower side is light green in colour.

So, the correct answer is ‘Upper surface is dark green as compared to the lower surface’.

In xerophytic leaves, mesophyll is differentiated into palisade and spongy parenchyma. In these leaves, palisade parenchyma is present on both sides. i.e towards upper epidermis and lower epidermis. In the palisade parenchyma cells are cylindrical in shape contains more number of chloroplasts. In spongy parenchyma, cells are oval in shape, loosely arranged, with less number of chloroplasts. 

The region present between the upper and lower epidermis of leaves is called mesophyll. It is differentiated into upper palisade and lower spongy parenchyma in dicot leaves or dorsiventral leaves, whereas in monocot leaves or isobilateral leaves, it is undifferentiated and it shows spongy parenchyma.

So, the correct option is ‘All dorsiventral leaves’.

Dorsiventral leaves orient themselves at an angle to the main axis and perpendicular to the direction of sunlight. Most dicots have dorsi-ventral leaves that are net-veined, including most trees, bushes, garden plants and wildflowers. Mesophyll is the ground tissue between the upper and lower epidermis. In dorsiventral leaf, it is differentiated into palisade parenchyma and spongy parenchyma. Palisade parenchyma lies towards the upper epidermis and consists of one, two or three layers of elongated cells, densely packed with no intercellular spaces and contains chloroplast

In the vascular bundles of dicot leaves, xylem and phloem are present on same radius and also present side by side. So they are called collateral and conjoint. Cambium is absent between xylem and phloem. So, It is called closed vascular bundle.

A dorsiventral organ is one that has two surfaces differing from each other in appearance and structure, as an ordinary leaf. This term has also been used as a synonym for dorsoventral organs, those that extend from a dorsal to a ventral surface. Dorsi-ventral leaves which usually orient at an angle to the main axis and held perpendicular to the direction of sunlight. An isobilateral leaf is usually vertically oriented to expose both surfaces to the sun. The leaves hang vertically to expose one face directly to the drying sun, then the other face. They have equal numbers of stomata in matching quantities and surface qualities of cuticle on both faces of the leaf. Epistomatic leaf has stomata on the upper surface only. Hypostomatic leaf having stomata on the underneath, i.e., foliar abaxial surface.

The adaxial (upper) surface of a bifacial leaf is typically exposed to more sunlight, so it has a thicker cuticle to prevent water loss, a darker color due to densely packed palisade parenchyma, and fewer stomata compared to the abaxial surface.

In a dorsiventral leaf the phloem is present towards the lower surface of the leaf. Xylem lies towards upper epidermis and is composed of annular and spirally thickened vessels, tracheids, fibres and xylem parenchyma. The vascular bundles are conjoint, closed and collateral. Mid vein bundle is large, while others are small. 

In dorsi ventral leaf, mesophyll is the ground tissue that occurs between the two epidermal layers. It is exclusively composed of chlorenchyma cells. The mesophyll is characteristically differentiated into two regions namely, an upper palisade parenchyma and a lower spongy parenchyma. Palisade parenchyma is composed of two or three layers of elongated, compactly arranged chlorenchyma cells. Intercellular spaces are absent. The cells contain a very large number of chloroplasts. Spongy parenchyma is composed of a few layers of loosely arranged spherical or oval chlorenchyma cells with prominent intercellular spaces. These cells contain very few chloroplasts. In isobilateral leaf, mesophyll is ground tissue that occurs between the two epidermal layers. It is composed of many layers of loosely arranged, spherical or oval chlorenchyma cells. Intercellular spaces are prominent. Mesophyll is not differentiated in spongy and palisade tissue. 
Therefore, the correct answer is option B.