It was observed that the leaves of a plant started getting wilted. Name the tissue which might have blocked. State the role of this tissue in plants.

ii. Explain opening and closing of stomata with the help of labelled diagrams.


iii. Name the physical phenomenon by which exchange of gasses occur between plant body and atmosphere.

1) The leaves of a plant started getting wilted, the tissue that might have blocked is Xylem. Wilting generally means drooping or falling due to lack of water. Xylem is responsible for water transportation, hence, it might have been blocked.


Role of xylem in plants:


i. It is a vascular tissue that helps in transportation.


ii. The xylem is responsible for the transport of water and minerals in the plants.


iii. It transports water from roots to the stem. Hence, its flow is only in one direction (unidirectional).


iv. Xylem also provides mechanical support to the plant.


v. The xylem has four different elements: tracheids, vessels, xylem fibres and xylem parenchyma.


vi. The xylem parenchyma stores food material in the form of starch.


2) Opening and closing of stomata:


• The opening and closing of stomata depend upon the guard cells.


• The guard cells are bean-shaped cells will allow as well as prevents the entry of water.


• When the water enters the guard cells, they swell. The swelling of guard cells results in the opening of the stomatal pore (also known as stomatal aperture).


• When the water flows out of the guard cells, the guard cells shrink, and the pore closes.


• The open and closed stomata are shown in the diagram below:



3) The physical phenomenon by which the exchange of gasses occur between plant body and atmosphere Respiration.


During respiration the plant uses O2 and form energy and CO2, this carbon dioxide at night is released in the atmosphere whereas during day time this carbon dioxide is used in the process of photosynthesis to form food.


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