Xylem sap consists of mainly water and some solutes or mineral nutrients.
Phloem sap mainly consists of the sucrose, a kind of transport sugar which is a diasaccharide, hormones and amino acids are also found in phloem sap of the plants.
If you are provided with two tubes ( $A$ and $B$ ), where one is narrow and the other is relatively wider and if both are immersed in a beaker containing water as shown in the figure.
Why does B show higher water rise than A?
Aquaporins are integral membrane proteins. These form pores or channels in the membrane. The water can flow more rapidly through these pores to inside of the cell, as compared to the process of diffusion.
These are plumbing systems of the cells. These selectively conduct water in and out of the cells, while preventing the passage of ions and other solutes.
ABA (Abscisic Acid) is called a stress hormone.
A. How does this hormone overcome stress conditions?
B. From where does this hormone get released in leaves?
A. Stress hormone ABA (Abscisic Acid) gives signals to stomata to get closed, whenever there is scarcity of availability of water to the plant. This prevents the loss of water through transpiration by leaves. It also increases the tolerance of plants to various kinds of stresses.
B. It (ABA) is released or transported from stem apices to leaves.