園藝作物生物學題庫

二、以下文字取材自Holbrook, N.M. 2010: Xylem cavitation breaks the continuity of the water column and prevents the transport of water under tension. Such breaks in the water columns in plants are not unusual. When plants are deprived of water, sound pulses or clicks can be detected. The formation and rapid expansion of air bubbles in the xylem, such that the pressure in the water is suddenly increased by perhaps 1 MPa or more, resulted in high-frequency acoustic shock waves through the rest of the plant. These breaks in xylem water continuity, if not repaired, would be disastrous to the plant. By blocking the main transport pathway of water, such embolisms would increase flow resistance and ultimately cause the dehydration and death of the leaves, and other organs.