Botany and Plant Science

Phloem is a vascular tissue in land plants primarily responsible for the distribution of sugars and nutrients manufactured in the leaves of the plants by the process of photosynthesis.

a) Passage cells often occur in the endodermis.

b) Stomata are cells in the epidermis of leaves. It is also called accessory or subsidiary cells.

c) Sieve tubes are related to companion cells and both are portions of plant phloem.

d) Lenticels are spongy openings in the periderm. It helps in gaseous exchange.

e) Mesophyll of a leaf comprises palisade cells that work in the absorption of light for photosynthesis.

Thus the answer is matching "A−4, B−5, C−1, D−2, E−3".

The correct option is C.

The sieve tubes are the conducting vessels in the phloem tissue. These are the long tube like cells which have perforated transverse plates. These are the cells which are responsible for the conduction of food. The sucrose is the main sugar which is the form of carbohydrate stored in the plants. The sugar is transported through the phloem vessels from the source end (leaves) to sink end (roots). 

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.