Excessive soil and water boron (B) occur widely in California, often in conjunction with high soil salinity. Descriptions of the symptoms of B toxicity and quantification of its impact on Prunus species are not available. In these experiments we describe the impact of high B and saline conditions on uptake, distribution and growth depression in almond, peach, plum and peach/almond hybrid rootstocks
A series of experiments are described that indicate an important additive effect of B on sensitivity of Prunus species to salinity. Boron concentrations in excess of lppm in the irrigation solution, significantly impair plant growth under moderate (non-limiting) salinity conditions and lead to plant death at higher salinity levels. Symptoms of B toxicity in Prunus include stem necrosis and vascular occlusion. Unlike most other species, B does not appear to accumulate in the leaf margins and leaf symptoms are generally not observed. Differences in sensitivity of a range of Prunus species to B toxicity are described.
Initial results suggest that differences in rootstock sensitivity to B and salinity are the result of differential uptkake and partitioning of B, Na and Cl within the plant.