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  • Author or Editor: Rawia El-Motaium x
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Boron toxicity is a wide spread problem especially in arid and semiarid areas of the world. Boron toxicity can result in yield loss of many crop plants, especially stone fruits which are sensitive to high boron concentration. This study was designed to follow the effect of Ca+2 supplementation on partitioning of B at the plant organ level (leaves, stem, roots) and the subcellular level (the cell wall) using the stable isotope 10B.

Results demonstrate that calcium supplementation reduced B accumulation in plum and peach leaves by 31% at the low level (0.25 mM) and by 12% at the high B level (0.50 mM). Results indicate an effect of Ca on the uptake and distribution of 10B between plant organs.

Symptoms of B toxicity in peach (Lovell) include stem die back, necrotic brown spots on the stem and gum formation on the nodes, whereas in plum (Mariana), stem die back and gum formation, as droplets, on the lower leave's surface were the main symptoms.

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The influence of B and salinity [3 Na2SO4 : 1 CaCl2, (molar ratio)] on B toxicity and the accumulation of B, sodium, and SO4 in six Prunus rootstocks was evaluated. High salinity reduced B uptake, stem B concentrations, and the severity of toxicity symptoms in five of the six rootstocks. Forward and backward stepwise regression analyses suggested that stem death (the major symptom observed) was related solely to the accumulation of B in the stem tissue in all rootstocks. The accumulation of B and the expression of toxicity symptoms increased with time and affected rootstock survival. No symptoms of B toxicity were observed in leaf tissue. The Prunus rootstocks studied differed greatly in stem B accumulation and sensitivity to B. The plum rootstock `Myrobalan' and the peach-almond hybrid `Bright's Hybrid' were the most tolerant of high B and salinity, whereas the peach rootstock `Nemared' was very sensitive to high B and salinity. In all rootstocks, adding B to the growth medium greatly depressed stem SO4 concentrations. In every rootstock except `Nemared' peach, adding salt significantly depressed tissue B concentrations. A strong negative correlation between tissue SO4 and B was observed. Grafting experiments, in which almond was grafted onto `Nemared' peach or `Bright's Hybrid', demonstrated the ability of rootstocks to influence B accumulation and scion survival.

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