Plant Transport and Physiology

Exchange of gas (CO₂) and water is regulated by the opening and closing of stomata.

Transpiration can be defined as the process of loss of water from the surface of exposed aerial parts of water. It helps to translocate water and minerals and also provides cooling effect to plants during summers. 

The widening of stomatal pores is due to the presence of water content in excess in a plant.

Transpiration is partly physical and partly physiological process. 

Maximum transpiration takes place from the lower surface of the leaves. If this portion is greased, the loss of water taking place from the plant will be very less.

In submerged plants, stomata are present but they are not functional. Hence, they do not play any role in transpiration. 

The rate of transpiration decreases with increase in humidity. Higher the humidity in the atmosphere, the lower will be the rate of transpiration. 

Maximum stomata are present on the lower part of a leave so as to minimize the loss of water during transpiration. 

In transpiration, diffusion of water molecules takes place out of the plant cells. 

In garlic, alliin and the enzyme alliinase are normally separated, but they form allicin if the vacuole is broken.

Yes, it is the correct answer. The xylem is the vascular tissue through which water is transported in plants.

Phloem is the vascular tissue responsible for transporting food (sugars and nutrients) produced in leaves to other parts of the plant. This process is called translocation. Xylem transports water and minerals from roots upward, while cambium is a meristematic tissue for secondary growth. The question specifically asks about food transport.

Photosynthesis is the biological process where plants use sunlight, water, and carbon dioxide to synthesize their food (glucose). Transpiration is water loss through leaves, evaporation is liquid to gas conversion, and precipitation refers to rain or snow.

Correct answer. Xylem is one of the two types of transport tissues in vascular plants. Almost all plant cells produce primary cell walls. The major component of most primary walls in xylem is a disorganised network of cellulose fibrils, which allows the wall to stretch and expand as the cell grows. The secondary wall is deposited on the inner side of the primary wall during and after the cell has elongated or enlarged. The cellulose fibrils in the secondary wall are arranged in a regular fashion with alternating layers at fixed angles to the main axis of the cell. This reinforces the plant cell while preserving the elastic nature of the primary wall. Most of the cell types in xylem can be distinguished based on the shape and features of the secondary cell wall. The walls of tracheids are made up of lignin. Xylem parenchyma cells store water, mineral nutrients and carbohydrates, and respond to wounding. Sclerenchyma cells of xylem provide mechanical support, defense and water transport.

Correct answer. In older stems, the woody trunk is differentiated into two regions. The outer light coloured region is called sap wood or alburnum, and central dark coloured region is called heartwood or duramen. The cells of sapwood are living and functional. They take part in conduction of water and storage of food. The heartwood consists of dead cells. During the growth process, the rings of sapwood gradually process and convert into heartwood. The living cells of sapwood lose their protoplast and water content. The lumen of the xylem vessels gets blocked in growth of the parenchyma cells. Hence, both A and R are true.