Effects of nitrogen forms on the growth, ascorbateglutathione cycle and lipid peroxidation in developing seeds of vegetable soybean

Abstract

A pot culture experiment of nitrogen forms (NO3
¯
:NH 4
+
) with four ratios (100:0, 75:25, 50:50, and 25:75) in
nutrient solutions was conducted to examine the effects of nitrogen forms on the growth, ascorbate-glutathione
(ASC-GSH) cycle and lipid peroxidation in developing seeds of vegetable soybean. Results showed that the
best plant growth vigor was observed in NO3
¯
(75%), and then in NH4
+
(50%). The contents of ASC and dehydroascorbate (DHA), and DHA/ASC ratio in NO 3
¯
(75%) and NH4
+
(50%) maintained stable values, but obvious
increases were observed in NO 3
¯
(100%) and NH4
+
(75%). The GSH contents exhibited increasing trends, while
the increases in oxidized glutathione (GSSG) contents were only observed in NO3
¯
(100%) and NH4
+
(75%), in
which high GSSH/GSH ratios were observed. In NO3
¯
(100%) and NH4
+
(75%), the enzymes activities in ASCGSH cycle, including ascorbate peroxidase (APX, EC 1.11.1.11), dehydro -ascorbate reductase (DHAR, EC
1.8.5.1) and glutathione reductase (GR, EC 1.6.4.2), expressed increasing trends. Significant increases in lipid
peroxidation and hydrogen peroxide (H2O 2) generation were also observed in NO3
¯
(100%) and NH4
+
(75%) as
against NO 3
¯
(75%) and NH4
+
(50%). It was shown that the degree of oxidative damage was relatively low when
the ratio of nitrogen forms was 75:25, and this could be a good guidance on the nitrogen application in the
cultivation of vegetable soybean.