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Abstract
A reflectant containing Zn and Ca among others, sprayed on the leaves of globe artichoke, increased the reflectance of the leaf. Treated leaves were always cooler than control leaves. The abaxial leaf surfaces of treated leaves were always warmer than the adaxial surfaces. The adaxial surface of treated small leaves had a higher diffusion resistance than the abaxial ones or either surface of control leaves. Higher diffusion resistance probably is the reason for better survival of treated plants in semi arid environments. Treated plants used water more efficiently than control plants.
Abstract
Staminate clone Israel 502 and ‘Kerman’ and ‘Lassen’ pistachio (Pistacia vera L.) on two rootstocks showed remarkable drought resistance under runoff farming in the Negev desert highlands. During favorable seasons, root distribution was fairly uniform down to 240 cm. Moisture depletion fluctuated between 58 and 477 mm during 1971-1974 because of great differences in flood water availability and scant annual rainfall (54–163 mm). Soil moisture was depleted in all strata well below the wilting point throughout the growing season in 1973 and from mid-July in 1974. Shoot growth terminated within 4–5 weeks. Although trunk growth continued at an even rate until August 1–15, the relative increment was 4.2–7% higher with the staminate clone. Extreme drought from the autumn of 1972 through 1973 (58 mm water depletion) did not prevent bud differentiation and high yields per tree (12.0 kg for ‘Kerman’, 9.5 kg for ‘Lassen’) in 1974.
Abstract
Soil moisture use, shoot growth, fruit size, and yield of apricot (Prunus armeniaca) trees (cv. Hatif de Colomer) were measured under flood water-spreading conditions in the desert. Root distribution was estimated from interpretation of soil moisture data. A highly significant correlation was found between pooled values of past and current seasons' water depletion values and current season's yield. Relative maximum water depletion (on a daily use basis) occurred during fruit maturation. Maximum trunk growth occurred in spring. In some seasons a second, small peak occurred in the autumn.
Shoot growth usually terminated by the beginning of June, and maximum trunk rate growth was usually (except in 1967) attained shortly thereafter.
Trees survived the extremely dry 1968 season (no flood, and only 80 mm of rain), with partial recovery in shoot growth and yield and full recovery in trunk growth during the subsequent year.
Moisture depletion under the trees, per 1000 m2, during the active period of the trees (March to end of September) was only 26 mm in 1968, about 100 mm in 1966, 106 mm in 1967 and 146 mm in 1969. Yields per tree (26 trees per 1000 m2) ranged from 1.4 kg (in 1970) to 27.4 kg (in 1967).
The central cylinder around the tree (2 meters in diam) accounted for the highest relative use of water in comparison with other annuli extending around the tree.