Effect of root temperatures on growth of two avocado rootstock cultivars
1990
Whiley, A.W. | Wolstenholme, B.N. | Saranah, J.B. | Anderson, P.A.
Non-grafted, cloned avocado plants [Persea americana Mill.] of the Mexican [cv Duke 7] and Guatemalan [cv Velvick] ecological races were grown for twelve weeks in sunlit growth rooms with root temperatures controlled at 13, 18, 23 and 28 degrees C. Air temperatures in the rooms were profiled between 28 degrees C day maximum (15h00) and 18 degrees C night minimum (06h00). Root dry mass at the root temperature of 13 degrees C was lower than at 18, 23 and 28 degrees C. There was no significant difference in root dry mass between the two cultivars at any of the root temperatures. Shoot dry mass was greatest at 18, 23 and 28 degrees C with a significant reduction at 13 degrees C. At the root temperatures of 13 and 23 degrees C cv Velvick produced greater shoot growth than cv Duke 7. Leaf xylem water potential became more negative and stomatal conductance fell during the day regardless of root temperature. However, at all root temperatures the leaf xylem water potential of cv Duke 7 was more negative than cv Velvick at 14h00, and at 13 degrees C the stomatal conductance of cv Duke 7 fell more rapidly during the morning than cv Velvick. The results are discussed in relation to the relative performance of the rootstock cultivars.
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