A. Gur
Hebrew University of Jerusalem
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Featured researches published by A. Gur.
The Journal of horticultural science | 1976
A. Gur; Yosef Mizrahi; R. M. Samish
SummaryOne-year-old apple plants of several rootstock clones, and grafted plants belonging to several scion cultivare, were grown in sand cultures for eight to ten weeks under conditions of constant root temperatures.The optimal root temperature for development of the root system was 25°C for most rootstock clones, but 30°C for M 7, and the clones differed widely in the degree of damage caused to their roots by supraoptimal root temperature. The scion cultivar in grafted plants also contributed to the relative susceptibility of the whole plant. The order of relative susceptibility of clones was not maintained when root tip expiants, instead of whole plants, were cultivated at various temperatures. The temperature optimum for elongation of root tip expiants was considerably higher than that for root growth in intact plants.The chlorophyll content of leaves was reduced by supraoptimal root temperature, but the degree of chlorophyll reduction in the different clones was about the same when compared with that...
The Journal of horticultural science | 1979
A. Gur; J. Hepner; Y. Shulman
SummarySeveral ungrafted one-year-old apple rootstock clones and grafted scion cultivars were grown at constant root temperatures, between 20°C and 35°C, either in sand cultures for 8-11 weeks or a clay soil for 11 to 14 months. Root temperatures exceeding 25°C with several rootstock clones and 30°C with others decreased the K and Zn content of all parts of the plants. This decrease was accompanied by increases in the Na, Ca and Mg contents of the roots, and at 35°C in the Na and Mg of the leaves also. The content of K+Ca+Mg+Na reached a maximum in the roots at 36°C and in the tops at 29°C. A root temperature of 35°C lowered the total N content of the leaves. Supplying K salts by fertilization or foliar spray to plants at a root temperature of 29°C increased the K content of the roots and leaves, but no such effect was found at 36°C. The spray treatment was particularly effective in raising the root K content at 29°C. All treatments with K caused a shift in the distribution of the Ca in the plant, reducin...
Scientia Horticulturae | 1986
A. Gur; Arie Altman; R. Stern; B. Wolowitz
Abstract With leafy peach ( Prunus persica (L.) Batch) cuttings under mist, the highest rooting percentage, the largest number of roots per rooted cutting and the highest survival rates of the rooted cuttings were obtained by treating the bases of the cuttings for 24 h with a solution of 50 mg l −1 indolyl butyric acid (IBA) + 500 mg l −1 2,3-dichloro-1,4 naphthoquinone (dichlone). However, in the absence of dichlone, an IBA concentration of only 25 mg l −1 was optimal for rooting. Weekly sprays with a mixture of benzyladenine (BA) and naphthaleneacetic acid (NAA) increased the percentage of rooted cuttings in the poorly rooting cultivar ‘15–39’. Treatments to decrease the severe leaf-drop which occurred during the hardening-off period, i.e. weekly sprays with BA + NAA or with an anti-transpirant (TAG), if started at the beginning of the hardening-off period, considerably improved the survival of the rooted cuttings and their cytokinin content. Even more efficient in this respect were weekly sprays with a mixture of benzyladenine and myo-inositol, apparently due to an enhancement in the BA transport to the root system. This explanation is supported by the very marked accumulation of cytokinins in the roots of cuttings which had been sprayed with a mixture of myo-inositol and benzyladenine compared to plants which had been sprayed with benzyladenine alone. On the other hand, application of BA to leaves resulted in the inhibition of the transport of apically applied MI to the bases of the cuttings. Better leaf retention was related to increased levels of sugars in the cuttings. In the newly formed root system of the cuttings, a high cytokinin content was related to a high sugar content.
The Journal of horticultural science | 1976
A. Gur; J. Hepner; Yosef Mizrahi
SummaryOne-year-old apple plants were grown with controlled root temperature, either in sand cultures or in a sandy loam or clay soil. Experiments lasted 10 weeks in sand culture, and 11 months in the two soil types, starting in late summer, but without applying the controlled temperature treatments in winter and spring.A temperature of 29°C reduced root and shoot growth, when applied for a relatively long period, compared with 22°C or 25°C. At 35°C shoot growth was affected even when the experiment lasted only 10 weeks. The root : shoot ratio also decreased with rising temperature. The reduced shoot growth was due to a decrease in the number of nodes. Total leaf weight of the plants was reduced by supraoptimal root temperature in short-term experiments, but in long-term ones this was largely compensated by the formation of many spur-type branchlets bearing a large number of small leaves. The proportion of dry matter in the roots decreased at supraoptimal root temperatures.The deleterious effect of suprao...
Scientia Horticulturae | 1991
Y. Cohen; A. Gur; Z. Barkai; A. Blumenfeld
Abstract Persimmon trees ( Diospyros kaki L.) grafted on Diospyros virginiana L. rootstock seedlings frequently grow very poorly and show several decline symptoms. Rootstock and scion girths of declining trees were smaller than those of healthy trees. Trees grafted on D. kaki rootstocks did not decline. In declining trees, the wood colour close to the graft union changed from yellow to brown, and gum accumulated in the phloem rays and xylem vessels, partly blocking them. The water transport in this area was impeded and the water potential of shoots of declining trees was less than that of healthy trees. Scions from both healthy and declining trees were grafted on the same healthy D. virginiana rootstocks. The healthy scions were influenced by their unhealthy neighbours and grew poorly. Plant material obtained from these originally healthy scions also grew poorly when grafted on healthy D. virginiana rootstocks, indicating that the healthy scions were somehow infected by their unhealthy neighbours. Removing scions of young declining trees and replacing them with healthy scions also resulted in reduced growth, compared with healthy rootstocks grafted with healthy scions. These results suggest the presence of a transmittable biotic factor, both in D. virginiana rootstocks and D. kaki scions, causing decline only in D. kaki scion tissues.
Scientia Horticulturae | 1991
A. Gur; Y. Cohen; J. Katan; Z. Barkai
Abstract Preplant soil fumigation with several chemicals increased the circumference and the yields of apple trees, following apples, and of peach trees on peach seedling rootstock following peaches on peach or almond rootstocks. With both apples and peaches a mixture of 70% methyl bromide (MB) and 30% chloropicrin (CP) or the two chemicals applied separately to the same plot was more effective than applying only one of them. With peaches on peach rootstock following peaches on the same rootstock, heating the soil by solar energy (solarization) with and without the fumigation with a small amount of MB was found to be much less effective than the double fumigation, first with CP and then with MB. Replanted peach trees were affected by the peach replant disease to the same degree if planted between, rather than on, the site of the uprooted trees.
The Journal of horticultural science | 1976
A. Gur; B. Bravdo; J. Hepner
SummaryOne-year-old M 2 apple trees were grown at three constant root temperatures (22°, 29°, and 36°C) in containers filled with either clay soil or a sandy loam.Rates of photosynthesis and transpiration measured four months after the start of the experiment decreased with rising soil temperature; the former more sharply in the sandy loam than in the clay soil. The potassium and chlorophyll content of the leaves decreased significantly with increasing soil temperature only from 29° to 36°C. Leaf water potential decreased, while the resistance of the leaf to the loss of water vapour, and the shoot : root dry weight ratio increased with rising temperature. The water content of the roots increased with rising temperature and that of the leaves decreased. The water content of both roots and leaves was as a rule lower in clay soil than in sandy loam.All these effects at 36°C soil temperature were significantly reduced by the application of potassium sulphate to the soil at the start of the experiment. The red...
Scientia Horticulturae | 1974
A. Gur; Yair Oren; Naftali Zieslin
Abstract Several factors contributing to the successful rooting of stem cuttings of four peach clones and one almond × peach hybrid under intermittent mist were tested. With the almond × peach cross, leaf-bud cuttings were also tested. Severe cutting back of adult peach mother trees in winter favoured rooting of the cuttings, but less severe cutting back induced maximum roots per cutting. For short periods vermiculite was found to be a suitable medium. Sand alone or mixed with vermiculite or gravel gave poor results. Gravel alone or mixed with vermiculite was intermediate. For growing the rooted cuttings for a longer period, a mixture of perlite and peat was very suitable. A period of illumination of 3 h starting at midnight with incandescent light improved rooting of peach cuttings in August and October, but not in June. With cuttings obtained from old fruit-bearing peach trees highest rooting rates were obtained in July, but best root development occurred when rooting was carried out in October. In July rooting rate of basal cuttings was much higher than that of terminal ones. Success with leaf-bud cuttings (including a small branch piece) obtained from young mother trees of the almond × peach hybrid was only achieved at the end of May or in June. Dipping the base of peach cuttings in water before rooting was of advantage with one cultivar rooted in September, but of no advantage with another cultivar rooted in June. When the base of stem cuttings was dipped for a prolonged period in IBA solutions of various concentrations, highest rooting rates were obtained with 25–50 ppm IBA for peaches and with 200 ppm for the almond × peach hybrid. The addition of Phygon XL to this solution was of some advantage for peach cuttings. The concentration inducing maximum root development was higher than that required for maximum rooting and callusing. The optimal IBA concentration for rooting of almond × peach leaf-bud cuttings was 100 ppm. Penetration of the IBA into the leaf-bud cuttings reached a maximum 45 min a after floating them on a 100 ppm solution. Transplanting cuttings which had been rooted under mist was somewhat difficult; however, high rates of survival were obtained with cuttings planted in September which had developed a good root system.
Archive | 2000
A. Gur
Among the detrimental effects of warm climates on temperate fruit crops, supraoptimal root temperatures may be of considerable importance, the optimal temperatures varying according to the species involved. Even if we disregard the temperature in the upper 5 cm of the soil, which may reach extremely high levels in subtropical countries, soil temperatures exceeding 30°C are to be found in areas growing deciduous fruit trees as in parts of the U.S.A, Japan, Israel, Australia, Turkey and Greece (Ashbel et al., 1965). Mulching and frequent drip irrigation reduces temperatures in the root zone, but still the damage caused by supraoptimal root temperature has to be considered.
Physiologia Plantarum | 1972
A. Gur; Ben-Ami Bravdo; Yosef Mizrahi