Decrease of boron cross-linking ratio and morphological change in tomato plants under boron deficiency

Abstract

ABSTRACT In tomato (Solanum lycopersicum L.), morphological changes caused by boron (B) deficiency were investigated. The B cross-linking ratio in cell walls and accumulation of reactive oxygen species (ROS) were determined in organs where physiological disorders and necrosis occurred. Under B deficiency in tomato, leaf colour turned yellow, plant height and stem diameter were shorter, and the shoot apex or flower bud necrosis was observed. The morphologically abnormal fruits, such as uneven, uneven black, and corky fruits appeared. The B cross-linking ratio was significantly decreased in the leaves and those abnormal fruits, which caused growth inhibition under B deficiency. By anatomical observation, the surrounding thickened cell walls of collenchyma cells decreased, and the arrangement of cells in the cortical layer and cambium was disordered in the stem. Cell necrosis was observed around the vascular bundle and in the flower bud. B cross-linking ratio significantly reduced in the parts with morphological abnormalities, which may decrease the mechanical strength of the cell wall. ROS accumulated, and necrosis occurred in the flower bud due to B deficiency. It was considered that B deficiency inhibits B cross-linking in the cell wall and induces ROS accumulation, causing cell collapse and necrosis.