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Ceratonia siliqua

Fig. 2.2.11. Dependence of cavitation in xylem vessels of different size on the water potential in the xylem as the soil dried over several days. At a water potential of approximately -3.3 MPa all large vessels of Ceratonia siliqua (>60 pm), but only 10% of the small vessels (< 10 pm), are cavitated

Fig. 2.2.11. Dependence of cavitation in xylem vessels of different size on the water potential in the xylem as the soil dried over several days. At a water potential of approximately -3.3 MPa all large vessels of Ceratonia siliqua (>60 pm), but only 10% of the small vessels (< 10 pm), are cavitated

Another pointer to the limiting role of the xylem structure for water transport is given by the measurement of water flow in the xylem of pines of different ages in the continental climate of central Siberia (Fig. 2.2.12; Zimmermann et al. 2000). In pines, the xylem flow increases linearly with the sapwood area. The greatest sapwood area is achieved at the age of 60 years. At this age the growth of trees is relatively high and the formation of heartwood has not yet started. For very old pines the sapwood area decreases and thus the flow of water. Sapwood area results from growth of annual tree rings and hardwood formation.

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