DENDROLOGY

TREE PHYSIOLOGY

RESPIRATION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Water travels ____ the plant, through the ____
A
up, phloem
B
down, phloem
C
up, xylem
D
down, xylem
Explanation: 

Detailed explanation-1: -Xylem transports water, minerals, and nutrients from the soil to all the plant parts. There are two types of “transport” tissues in plants-xylem and phloem. Water and solutes are transported by the xylem from the roots to the leaves, and food is transported from the leaves to the rest of the plant by the phloem.

Detailed explanation-2: -The tension created by transpiration “pulls” water in the plant xylem, drawing the water upward in much the same way that you draw water upward when you suck on a straw. Cohesion (water sticking to each other) causes more water molecules to fill the gap in the xylem as the top-most water is pulled toward the stomata.

Detailed explanation-3: -Once water is in the xylem, it travels upwards-against the force of gravity-towards the rest of the plant. Water is able to move against gravity due to two forces: tension and cohesion. Tension is a ‘sucking force’ which is created when water evaporates from leaves (transpiration), pulling more water into the leaf.

Detailed explanation-4: -The vascular tissues of these plants are called xylem and phloem. The xylem of vascular plants consists of dead cells placed end to end that form tunnels through which water and minerals move upward from the roots (where they are taken in) to the rest of the plant.

Detailed explanation-5: -Continuous transpiration occurring in all of the leaves of a plant creates a negative pressure in the water column (xylem). This exerts an upward pull on the water column, called transpiration pull. And thus, the water present in the xylem column transports up to the tip of the stem, leaves, etc.

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