摘要：

为探究高温胁迫下不同浓度外源GABA对番茄幼苗干物质积累、根系发育、抗氧化酶活性及光合特性的影响。选用番茄品种粉特利为试材,设置叶面喷施清水(CK)、1 mmol/L GABA(T1)、5 mmol/L GABA(T2)、10 mmol/L GABA(T3)、20 mmol/L GABA(T4)5个处理。每2 d进行1次喷施,连续喷施2次。然后,将幼苗置于40 ℃/35 ℃(昼/夜),14 h(光)/10 h(暗),光强250 μmol/(m²·s)条件下,高温胁迫处理7 d。结果表明,与CK相比,叶面喷施10 mmol/L及以下浓度的GABA(T1、T2和T3)显著促进番茄幼苗的生长,其中株高、茎粗、地上部干物质量和壮苗指数分别提高4.96%~6.92%,7.65%~19.26%,29.41%~52.94%和20.00%~26.67%。其中,T2较CK处理,显著提高了根系的总根长、总表面积、总体积和根尖数,增幅分别为23.04%,13.95%,11.76%和18.30%。此外,与CK相比,T2处理会通过增加叶片的(超氧化物歧化酶)SOD、(过氧化物酶)POD和(过氧化氢酶)CAT酶活性(增幅分别为22.58%,51.73%和148.80%),同时降低叶片的相对电导率和丙二醛含量(降幅分别为12.84%和21.89%),从而保证叶片细胞膜结构和功能的完整,进而提高叶片的光合速率、气孔导度和蒸腾速率(增幅分别为 81.38%,36.19%,41.26%)。然而,高浓度的GABA(T4)与CK处理的幼苗干物质积累、光合特性及叶片相对电导率差异不显著,甚至会抑制根系的生长发育。综上,叶面喷施适宜浓度的GABA既可通过提高叶片渗透调节能力和抗氧化酶活性,保护叶片细胞膜的完整性,进而缓解高温胁迫对光合作用的抑制,亦会通过促进番茄幼苗干物质积累和根系发育,从而提高番茄幼苗的耐热性。本试验条件下,以5 mmol/L的GABA效果最优。

关键词: 番茄幼苗, γ-氨基丁酸, 高温胁迫, 抗氧化酶活性, 光合特性

Abstract:

In order to explore the effects of different concentration of exogenous GABA on tomato seedlings dry matter accumulation,root development,antioxidant enzyme activities and photosynthetic characteristics under high temperature stress,the tomato variety Fenteli was selected as the test material,and five treatments,including spraying distilled water (CK),1 mmol/L GABA(T1),5 mmol/L GABA(T2),10 mmol/L GABA(T3)and 20 mmol/L GABA (T4),were set up in this study. Spraying once every two days for two consecutive times. After spraying,the seedlings were exposed to high temperature stress at 40 ℃/35 ℃ (day/night),14 h (light)/10 h (dark)with light intensity of 250 μmol/(m²·s)for 7 days. The results showed that compared with CK,spraying GABA with the concentration of 10 mmol/L or less (T1,T2 and T3)significantly promoted the growth of tomato seedlings,and the plant height,stem thickness,aboveground dry weight and seedling index increased by 4.96%—6.92%,7.65%—19.26%,29.41%—52.94%,20.00%—26.67%,respectively. Noteworthy,compared with CK,T2 treatment significantly increased the total root length,total surface area,total volume and tip numbers of root system by 23.04%,13.95%,11.76% and 18.30%,respectively. Moreover,compared with CK,T2 treatment not only increased the leaves activities of SOD,POD and CAT in (increasing by 22.58%,51.73% and 148.80% respectively),but also decreased the relative conductivity and malondialdehyde content (decreasing by 12.84% and 21.89%),and thus significantly increasing the photosynthetic rate,stomatal conductance and transpiration rate of leaves (increasing by 81.38%,36.19% and 41.26% respectively)by ensuring the integrity of the cell membrane structure and function of leaves. However,there were no significance differences for the dry matter accumulation,photosynthetic characteristics and relative conductivity of tomato seedlings under T4 and CK treatments,and even the former inhibited the root development. In a word,our study demonstrated that foliar spraying with an appropriate GABA concentration could alleviate the inhibition of photosynthesis under high temperature stress through protecting the integrity of leaf cell membrane by improving capacity of leaf osmotic adjustment and antioxidant enzyme activities. Additionally,spraying GABA could also improve the heat tolerance of tomato seedlings by promoting dry matter accumulation and root development. The effect of GABA with 5 mmol/L was the best in this study.

Key words: Tomato seedlings, GABA, High temperature stress, Antioxidant enzyme activity, Photosynthetic characteristics