Movement of xylem sap from roots to leaves movement of xylem sap from roots to leaves usually depends on tension, or negative pressure potential depends on the pumping of water through aquaporins occurs through the apoplast of sieve-tube elements depends on active transport

Movement of xylem sap from roots to leaves usually depends on tension, or negative pressure potential.

Explanation:

Movement of xylem sap from roots to leaves usually depends on tension, or negative pressure potential. Plants do not have a circulatory system like that of some animals. If a water molecule did "circulate" it would require the activity of transporters (like the circulatory system in animals) i.e help of the xylem and phloem. Xylem sap is a mixture/solution of water and minerals that comes from the roots and moves up the plant through the xylem. It is transported long distances by bulk flow to the veins. What causes it to move upward is the cohension-tension theory along with transpiration. In other words, transpiration provides the pull, cohesion of water molecules transmits this pull along the entire length of the xylem from roots to shoots. The basis of the transpirational pull lies in the fact that the pressure is created by proton pumping of stomatal guard cell. The pressure potencial can be described as the physical pressure on a solution; can be positive or negative relative to atmospheric pressure. In the case of the movement of xylem sap from roots to leaves it is negative.

hygrometers and hair thermometers (often found as part of hygrometers/psychrometers) can be used to measure humidity. barometers are used to measure atmospheric pressure, while anemometers are used to measure wind speed. so the 2nd and 4th choices should be the correct answers.

chronological thinking is an indispensable tool to structure a historical narrative and to give meaning to a sequence of events. the final section presents the results of a survey to test the chronological thinking of lower secondary school students carried out by the educational research institute.