effects of b toxicity on vegetative growth, physiological characteristics and boron distribution in two scion-rootstock combinations of almond (prunus dulcis mill.) tree

boron (b) toxicity is an important disorder that can limit plant growth in arid and semi-arid environments. it has been proven that use of tolerant rootstocks impede b uptake or transport to the aerial portions of plants. this may alleviate b toxicity in the scion, consequently improves the tolerance to excess b in the root zone. an experiment was conducted to find the effects of b toxicity on vegetative growth, physiological characteristics and b distribution of almond tree (prunus dulcis mill.) cv. “ferragnes” grown in the controlled environment. three levels of b (0.25, 10, 20 mg/l) from h3bo3 and two almond rootstocks (gf677, tuono) were factorially combined in a completely randomized design with four replications. the results showed that b toxicity had significant effects on vegetative growth, physiological characteristics and b distribution in almond tree. with increasing b levels in nutrient solution, vegetative characteristics including leaf production percentage and main shoot elongation was decreased significantly. however, fr/tuono was affected less than fr/gf677. also, physiological characteristics such as electrolyte leakage percentage, proline content and leaf necrosis percentage were increased significantly in two scion-rootstock combinations. on the basis of these results, gf677 because of an inability to restrict uptake and/ or transport of excess b from root system to aerial parts of scion, have a higher sensitivity to b toxicity. instead, tuono via mechanism of preferential distribution of b in roots inhibited the accumulation of high concentration of b either in young leaves or meristematic tissues partially and protected these susceptible organs against injury caused by b toxicity. in conclusion, it seem that under excess b conditions tuono rootstock have higher tolerance than gf677.