Effects of Zn treatment on physiological characteristics, photosynthesis, ultrastructure of root tip cell and grain Zn accumulation in different varieties of rape

Abstract

Aims Our objectives were to reveal differences in physiological characteristics, photosynthesis, ultrastructure of root tip cell and grain Zinc (Zn) accumulation in different varieties of rape under different Zn treatments. Methods Pot experiments were carried out. Zn treatments were 0, 1.0, 5.0, 10.0 and 20.0 mg·kg –1 , and five va-rieties of rape were ‘Luopingjincaizi’ (Brassica juncea), ‘Erniuwei’ (B. juncea), ‘Liyangkucai’ (B. juncea), ‘Nan-tonghuangyoucai’ (B. chinensis) and ‘H33’ (B. napus). All experiments were performed in triplicate, and pots were arranged in a completely randomized design inside a greenhouse. Important findings The dry weights of roots, leaf, straw, grain and plant, physiological characteristics and con-centration and accumulation of Zn significantly differed among the different varieties and Zn treatments. The ac-tivities of antioxidant enzymes, net photosynthetic rate (P n ), stomatal conductance (G s ), transpiration rate (T r ), and dry weights of plant, straw, leaf and grain increased at Zn ≤ 5.0 mg·kg –1 . The highest yields of grain for the five varieties were all observed in the 5.0 mg·kg –1 Zn treatment and were 37.7%, 23.4%, 29.5%, 82.6% and 18.0% greater than the control, respectively. Ultrastructural damage was found in the root-tip cells for ‘Luopingjincaizi’, ‘Erniuwei’, ‘Nantonghuangyoucai’ and ‘Liyangkucai’ in the presence of 20.0 mg·kg –1 Zn and included mitochon-dria inflation, cell-wall thickening, nucleus atrophy and decreased contents of nucleus, while unaltered structure of the root-tip cells was observed in ‘H33’. Grain Zn accumulation for the five varieties increased at Zn ≤ 5.0 mg·kg –1 , and decreased at Zn 5.0 mg·kg –1 . Highest concentration and accumulation of Zn in grains were ob-served in ‘Erniuwei’ at 5.0 and 10.0 mg·kg –1 Zn (172.34 mg·kg –1 , 2.932 mg·pot –1 and 164.10 mg·kg –1 , 2.575mg·pot –1 ) treatment, respectively.