| The objectives of this study were to investigate the influence of γ-aminobutyric acid(GABA)application and light on the yield,quality and 2-acetyl-1-pyrroline(2AP)formation and its physiological basis.Three experiments were conducted at the Teaching and Experimental Farm of College of Agriculture,South China Agricultural University,during2016 to 2018.Experiment 1,the fragrant rice varieties Meixiangzhan 2 and Yuxiangyouzhan were used as the planting materials in the pot experiment,while in the field experiment,the fragrant rice varieties Meixiangzhan 2,Yuxiangyouzhan,Basmati,Xiangyaxiangzhan and Yungengyou 14 were used as the planting materials.Four GABA spraying stages were set up:S1 was tillering stage,S2 was panicle differentiation stage,S3 was heading stage,S4 was all the three stages above,and the control(CK)was no GABA spraying.Experiment 2,the fragrant rice varieties Xiangyaxiangzhan and Yuxiangyouzhan were used as the planting materials in the pot experiments.Supplementary light was applied to the fragrant rices at the booting stage and the filling and ripening stage,respectively,including three light treatments:L1 was supplementary red light,L2 was supplementary blue light,and L3 was supplementary red,blue and white light(RBW);and the control(CK)was conventional light.Experiment 3,the fragrant rice varieties Basmati,Yuxiangyouzhan and Yungengyou 14 were used as the planting materials both in the pot experiment and field experiment.Conventional light treatment without GABA spraying was used as control(CK),two treatments were set up: T1 was not sprayed with GABA under the low light condition,T2 was sprayed with GABA under low light condition.The yield,quality and 2-acetyl-1-pyrroline(2AP)formation and its physiological basis was investigated.The results are mainly as followed:(1)Exogenous GABA promoted the accumulation of 2AP in grains of fragrant rice,and the accumulation of aroma was related to the content of 1-pyrrolide-5-carboxylic acid,proline,GABA and diamine oxidase activity in grains.The content of 2AP in grains at maturity increased by 13.64% to 43.01% under S3 treatment and by 15.09% to 59.42% under S4 treatment.On the premise of balancing the yield and quality of fragrant rice,and the cost of growing rice,spraying GABA at the heading stage(S3)was most beneficial to increase the content of 2AP in grains at maturity and improve the yield and quality of fragrant rice.(2)Supplementary red light,blue light or RBW light at booting stage and the filling and ripening stage decreased 2AP and protein contents in grains but increased grain yield of fragrant rice.Among them,the decrease of 2AP content was the greatest with supplementary blue light(L2)at booting stage(21.86-22.82%),and with supplementary red light(L1)at the filling and ripening stage,reaching 14.06% to 29.56%;and the change of 2AP content was related to the content of 1-pyrrolid-5-carboxylic acid and the content of GABA in grains.The yield was significantly increased by 34.50% under supplementary RBW light treatment(L3)at the booting stage;while at the filling and ripening stage,the yield of supplementary red light treatment(L1)was significantly increased by 14.86-19.45%,and the yield of supplementary RBW light treatment(L3)was increased by 18.61-21.37%.(3)Compared with CK,the 2AP content in grains at maturity under low light was increased,but the yield was decreased;when comparing to T1 treatment,T2 treatment increased the yield of fragrant rice by 32.82-34.80%,proving that the application of GABA could balance the yield and aroma of fragrant rice under low light condition.The content of2 AP increased by exogenous GABA application under low light condition was related to the content of proline and GABA,the activity of ornithine transaminase and diamine oxidase,and the content of sodium(Na)and manganese(Mn)ions in grains.In addition,the increase of yield of fragrant rice under GABA spraying treatment may be related to yield components(such as grain number per panicle and seed setting rate). |
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