Pure water has tremendous free energy at normal room temperature. That is called water potential. When the water temperature drops down, the free energy is reduced so, sugar does not get dissolved easily in, i.e., cold water.

Salt solution being hypertonic, causes exo-osmosis in plants. 1 cup salt in 2 cup of water, fairly well dissolved when sprayed on weed plants, start killing them. This salt concentration is then increased in subsequent sprays, if the weeds are still thriving in the field.

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.

The tube $B$ will show higher level than tube $A$ because of the capillary action.

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.