M. Urrestarazu et al., A DAILY RHYTHMIC MODEL FOR PH AND VOLUME FROM XYLEM SAP OF TOMATO PLANTS, Communications in soil science and plant analysis, 27(5-8), 1996, pp. 1859-1874
Ten-day-old tomato plants (Lycopersicon esculentum Mill. cv. Rambo) we
re transplanted in a NFT special system. The experiment was repeated t
hree consecutive times. Each experiment consists of three replicates.
The experiments were carried out first with 30-day-old plants and subs
equently with plants which were 45-days-old. The sap flux rates (V) va
ry considerably during the day at both harvest dates and there was has
highly significant correlation (p>0.999) with the chronophysiological
rhythm (Halberg, 1969) which has the highest rates in the day and the
lowest rates at night. The pH rhythm, which shows an opposite behavio
r of the sap flux rate, is related to organic anion equivalents (C-A).
A markedly difference in the behavior of C-A values occurred at both
harvest dates. The model presented in this paper may provide a framewo
rk for the explanation of short and long term V and pH fluctuation of
xylem sap. The changes in the pH of the xylem sap are probably normall
y buffered, but may have the possibility to influence processes locali
zed within the shoot.