Interactive Effect of Boron Toxicity and Rootstock on the Growth, Photosynthetic Rate and Nutrient Concentrations of Almond Tree

Boron 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 interactive effect of B toxicity and rootstock on vegetative growth, photosynthetic rate and nutrient concentrations of almond (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 randomized complete block design with four replicates. The results showed that the higher concentration of B had a significant diminish effects on vegetative and physiological characteristics as well nutrient concentrations of almond. The severity of the adverse effects of boron toxicity varied among rootstocks. Fresh and dry weights of leaf and root, leaf number, leaf area, photosynthetic rate and chlorophyll index was decreased with increasing B levels. Increased B levels led to decreased N, NO3-, P, K in the leaves while, B concentrations were increased. The concentration of B in stem was closely related to the development of B toxicity in rootstocks, imply that the mechanism of tolerance to higher B concentration in Tuono is associated with exclusion mechanism such as restrict B transport from root system to aerial parts. Hence, under excess B conditions Tuono can be used as tolerant rootstock for different almond cultivars