Botany and Plant Science

A.False – Secondary xylem formed during spring season, during the secondary growth of dicotyledonous stem is called Spring wood or early wood. It is light coloured and high density.

B.False - Secondary xylem formed during spring season, during the secondary growth of dicotyledonous stem is called Spring wood or early wood. It is light coloured and high density.

C.False – Secondary xylem formed during autumn season, during secondary growth of dicotyledonous stem is called autumn wood or late wood. It is dark coloured and high density.

D.True - Secondary xylem formed during autumn season, during secondary growth of dicotyledonous stem is called autumn wood or late wood. It is dark coloured and high density.

So, the correct option is ‘Autumn wood- dark colour, high density’.

In dicotyledonous stems, during intra stelar secondary growth, a ring of cambium called vascular cambium is formed.  Vascular cambium produces more amount of secondary xylem towards its innerside, and less amount of secondary phloem towards innerside. In the plants growing temperate regions, the activity of vascular cambium is influenced by existence of maximum seasonal variations. In the spring or early summer, due to the existence of favorable conditions, large amount of secondary xylem is formed. it is called Springwood or early wood. It is lighter in colour with low density. In the autumn season, due to the presence of unfavorable conditions, less amount of wood is formed. it is called autumn wood or late wood. It is darker in colour with higher density.

So, the correct answer is 'Depends on season and region where the plant grows'.

Some of the dividing pericycle cells are committed to the asymmetric, formative divisions that give rise to lateral root primordia and lateral root formation. The endodermis is the central, innermost layer of cortex in some land plants. It is made of compact living cells surrounded by an outer ring of endodermal cells with hydrophobic substances (Casparian Strip) to restrict the apoplastic flow of water to the inside. Sapwood is the soft outer layers of recently formed wood between the heartwood and the bark, containing the functioning vascular tissue and not central, dark colored, non-conducting part of secondary xylem.

 In a typical monocot root, Epiblema is single layered, consists of thin- walled cells. A few tubular root hair arise as unicellular elongation of epiblema cells.

The epidermis is a single-layered group of cells that covers plants leaves, flowers, roots and stems. It forms a boundary between the plant and the external environment. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds, and especially in roots absorbs water and mineral nutrients. 

A cuticle is the waxy layer present on the epidermis of a young stem which generally curtails the water loss by transpiration.

The epidermis cells are the cells which form the outer layer and plays an important role in protection. It helps to prevent the water loss by transpiration. Nerium, is a xerophyte which has layers of epidermal tissue to curtail the rate of transpiration. It is a type of xerophytic adaptation.
Thus, the correct answer is option D.

Laticiferous vessels are the specialized thin walled parenchymatous cells that secrete latex and are found in the cortex. They lack pits and are composed of cellulose and hemicelluloses and serve to secrete latex. Epidermis is the outermost covering of the primary plant body and is mostly represented by a single layer of compactly arranged, barrel-shaped parenchyma cells.
The innermost layer of cortex forms endodermis which has compactly arranged barrel shaped cells. The primary thin walled endodermis shows suberin deposition in form of bands or strips that run around the radial and end walls of the cells and forms casparian strips. Vascular bundle consists of xylem, phloem and cambium (in dicot only) which are derived from procambium and serve in translocation of food and sap.
Thus, the correct answer is option A.

The apical meristem has upper promeristem and lower primary meristem. Primary meristem differentiates into three distinct meristematic regions, the outermost protoderm, middle ground meristem, and innermost procambium. The protoderm gives rise to epidermal tissue system, ground meristem forms cortex/ground tissue system and procambium forms vascular tissue system (xylem, phloem, and cambium). 

• Cork cells are dead and have cell walls composed of a waxy substance "suberin", which is highly impermeable to gases and water. This substance prevents water loss from stem. Therefore, option B is correct.

The ground tissue system synthesizes organic compounds, supports the plant and provides storage for the plant. It is mostly made up of parenchyma cells. Parenchyma cells synthesize and store organic products in a plant. Parenchyma cells in leaves control photosynthesis. Collenchyma cells have a support function in plants, particularly in young plants. Mesophyll tissue is the photosynthetic parenchyma cells that lie between the upper and lower epidermis layers of a leaf. In dicotyledonous leaves, there are two types of mesophyll cells; palisade mesophyll and spongy mesophyll.

The epidermis cells is a single layer of cells that covers the leaves, flowers, roots and stems of plants. It forms a boundary between the plant and the external environment. Cork cambium is a tissue found in many vascular plants as part of the periderm. The cork cambium is a lateral meristem and is responsible for secondary growth that replaces the epidermis in roots and stems. The pericycle is a cylinder of parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele of plants. Cortex, in plants, the tissue of unspecialized cells lying between the epidermis (surface cells) and the vascular, or conducting, tissues of stems and roots. 

A root hair is the minute structures generally, present on the stem and the roots. It is a tubular outgrowth of a trichoblast, a hair-forming cell on the epidermis of a plant root.

The epidermis is a single layer of cells that covers the leaves, flowers, roots and stems of plants. It forms a boundary between the plant and the external environment. Its main function is protection. It has small opening known as stomata.

Bulliform cells  are so called because of its peculiar bubble shape. It mainly occurs on the upper surface of the leaves present in grasses. Water present in these cells helps to maintain its shape but loss of turgor pressure during the stress allows the leaves to roll up. During drought, the loss of moisture through vacuoles induces bulliform cells to cause the leaves of many grass species to close as the two edges of the grass blade fold up toward each other. Once adequate water is available, these cells enlarge and the leaves open again.