[Influence of exogenous gamma-aminobutyric acid (GABA) on GABA metabolism and amino acid contents in roots of melon seedling under hypoxia stress].

This paper investigated the influence of gamma-aminobutyric acid (GABA) on GABA metabolism and amino acid content under hypoxia stress by accurately controlling the level of dissolved oxygen in hydroponics, using the roots of melon 'Xiyu 1' seedlings as the test material. The results showed that compared with the control, the growth of roots was inhibited seriously under hypoxia stress. Meanwhile, the hypoxia-treated roots had significantly higher activities of glutamate decarboxylase (GAD), glutamate dehydrogenase (GDH), glutamate synthase (GOGAT), glutamine synthetase (GS), alanine aminotransferase (ALT), aspartate aminotransferase (AST) as well as the contents of GABA, pyruvic acid, alanine (Ala) and aspartic acid (Asp).

[Effects of exogenous gamma-aminobutyric acid on polyamine metabolism of melon seedlings under hypoxia stress].

Taking melon cultivar 'Xiyu No. 1 ' as test material, a hydroponic experiment was conducted to investigate the effects of exogenous gamma-aminobutyric acid (GABA) on the seedlings polyamine metabolism under hypoxia stress. Compared with the control in normoxic treatment, the seedlings under hypoxia stress had significantly higher glutamic acid decarboxylase (GAD) activity and GABA content, and their polyamine synthesis enzymes activities all enhanced significantly, which led to a marked increase of polyamines contents.

[Effects of gamma-aminobutyric acid on the photosynthesis and chlorophyll fluorescence parameters of muskmelon seedlings under hypoxia stress].

By the method of hydroponic culture, this paper studied the effects of exogenous gamma-aminobutyric acid (GABA) on the photosynthetic pigment contents, photosynthesis, and chlorophyll fluorescence parameters of muskmelon seedlings under hypoxia stress. Hypoxia stress induced a significant decrease of photosynthetic pigment contents, resulting in the decrease of photosynthesis. Applying GABA could significantly increase the photosynthetic pigment contents, net photosynthetic rate (P(n)), stomatal conductance (G(s)), intercellular CO2 concentration (C(i)), carboxylation efficiency (CE), maximal photochemical efficiency of PS II (F(v)/F(m)), photochemical quenching (q(P)), apparent photosynthetic electron transfer rate (ETR), and quantum yield of PS II electron transport (phi(PS II)), and decrease the stomatal limitation value (L(s)), minimal fluorescence (F(o)), and non-photochemical quenching (NPQ) under both hypoxic and normal conditions.