Leaf osmotic potential and osmotic adjustment in apricot under different water regimen during the years of establishment

Young apricot trees were subjected to different water regimes. Daily drip-irrigated plants were given 33%, 66%, 100% ET respectively; every 15th day sprinkled plants received a water depth equivalent to the cumulated ET of the period; no water was applied to the dry treatment. Leaf total (w) and osmotic (s) water potentials were measured every other week from April trough October, for three years following grafting. The third year the soluble sugar content of the leaves was also monitored. w varied according to the climatic course. It was slightly affected by irrigation, mainly in the last part of the season. s followed w throughout the season, thus giving evidence of a good osmotic adjustment. Soluble sugars content increased during the season while s lowered. In the first year, plants began to adjust their s, which continued to decrease in the subsequent years showing little variation with irrigation. More evident was the effect of water regime on turgor pressure ( p) indicating that this parameter provides more accurate information on the actual crop water status. It is desirable to increase water supply in August since drip-irrigated plants showed evidence of loss of turgor. Since a marked drop in p occurred late in the season in the sprinkler-irrigated treatment, as soon as irrigation was witheld, it seems appropriate to delay the end of irrigation.