Responses of Photosynthetic Performance of Sugar Beet Varieties to Foliar Boron Spraying

Abstract

The purpose of this experiment is to clarify the effect of boron application on leaves of different boron-sensitive beet varieties and to suggest a suitable recommendation for the management of extracorrhizal nutrients in beet production. Treatment included boron-tolerant variety (KWS1197) and boron-sensitive variety (KWS0143) with four levels of foliar boron spraying [0 (B0), 0.2% (B0.2), 0.4% (B0.4) and 0.8% (B0.8) boric acid]. The leaf properties, chlorophyll fluorescence parameters and mineral element content were determined. The results showed that boron spraying significantly increased the dry matter accumulation and leaves area of sugar beet. An appropriate amount of boron (B0.2 and B0.4) could significantly increase the net photosynthetic rate of leaves, SPAD value and PIABS, and best results were achieved with treatment B0.2. Boron spraying increased the PSII activity of leaves by increasing RC/CSm and ETo/ABS. The content of B in leaves increased significantly after boron spraying, while the content of Ca and Mg increased at the beginning and then decreased. At high boron stress (B0.8), SPAD value, PIABS and Mg contents of KWS0143 variety were recorded lower than those of B0, indicating that the photosynthetic process of the seedlings was inhibited. However, the KWS1197 variety had better physiological responses and stronger boron absorption ability. Comprehensive analysis revealed that B0.2 treatment was the optimal concentration for leaf spraying in beet, and excessive (B0.8) application of boron fertilizer would lead to boron toxicity, so as to reduced photosynthetic performance and inhibited the overall growth behavior of the beet.