Figure 4.
Role of xylem calcium in the light-induced increase in vulnerability to cavitation. Full sunlight-grown (white symbols) and shade-grown (black symbols) stems were sampled on four beech trees (four different symbols). They were perfused with NaPO4 solutions at pH 4 or pH 10, and the P50 values were scored. The section shows P50 values at pH 4 versus the shift in P50 values calculated as P50 pH4 − P50 pH10. Data are means (±se) of three to four samples. According to a repeated ANOVA analysis, the P50 pH4 means was significantly different between trees and between sunlight- and shade-grown stems, with P < 0.01. However, the means of P50 shift were not significantly different between trees (P = 0.226) and between full sunlight- and shade-grown stems (P = 0.899).