EFFECT OF ROOT TEMPERATURES ON GROWTH OF TWO AVOCADO ROOTSTOCK CULTIVARS

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°C. Air temperatures in the rooms were profiled between 28°C day maximum (15h00) and 18°C night minimum (06h00).

Root dry mass at the root temperature of 13°C was lower than at 18, 23 and 28°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°C with a significant reduction at 13°C. At the root temperatures of 13 and 23°C cv Velvick produced greater shoot growth than cv Duke 7. Leaf xylem water potential (_L) became more negative and stomatal conductance (g_s) fell during the day regardless of root temperature.
However, at all root temperatures the _L of cv Duke 7 was more negative than cv Velvick at 14h00, and at 13°C the g_s 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.

International Symposium on the Culture of Subtropical and Tropical Fruits and Crops

A.W. Whiley, B.N. Wolstenholme, J.B. Saranah, P.A. Anderson

https://doi.org/10.17660/ActaHortic.1990.275.15