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Abstract

Growth and biomass partitioning of almond trees [Prunus dulcis (Miller) D.A.Webb] were investigated in a semi-controlled pot experiment under arid conditions in the Negev Desert (Israel). Single trees of two varieties grafted on a local rootstock were grown for 1 to 4 years in pots of 3 in diameter and 1, 2 and 3 m depth, which resulted in 7, 14 and 21 m(3) soil volume. The pots were watered to field capacity once per year at the beginning of each growing season. Thus the plants received different amounts of water in relation to their biomass and leaf area as a function of their age and pot volume. This procedure resulted in different rates of soil drying and different stages of water deficit throughout the season, which allowed an investigation of the interactive effect of both seasonally varying water status and atmospheric conditions for a woody species in large soil volumes. We primarily tested whether a progressive reduction in the amount of water applied to the trees in relation to their leaf area would increase (1) biomass partitioning in favour of roots, especially fine roots, (2) the ratio of fine root length to leaf area. Neither biomass partitioning into leaves nor fine roots was significantly influenced by the amount of water supplied. There was no effect of water supply on the relationship between fine root length and finch root biomass (specific root length) either. Consequently, the relationship between length of fine roots and leaf area was not dependent on the amount of available water. The constant relationship between most of the biomass partitioning parameters examined in spite of the great range in water availability and over several years of growth is discussed as the result of the seasonal variation in the interaction of water supply and demand on tree growth and biomass distribution. [References: 31]