5-hydroxytryptamine (5-HT) participates in plant growth and development, and can also delay senescence and cope with abiotic stress. To explore the role of 5-HT in regulating the abilities of mangrove in cold resis-tance, we examined the effects of cold acclimation and the spraying of p-chlorophenylalanine (p-CPA, 5-HT synthesis inhibitor) on leaf gas exchange parameters and CO2 response curves (A/Ca), as well as the endogenous phytohormone content levels in the mangrove species Kandelia obovata seedlings under low temperature stress. The results showed that low temperature stress significantly reduced the contents of 5-HT, chlorophyll, endogenous auxin (IAA), gibberellin (GA), and abscisic acid (ABA). It weakened the CO2 utilization abilities of plants and reduced net photosynthetic rate, which ultimately reduced carboxylation efficiency (CE). Under low temperature stress, exogenous p-CPA reduced the contents of photosynthetic pigments, endogenous hormones, and 5-HT in the leaves, which aggravated the damages caused by low temperature stress on photosynthesis. By enhancing cold acclimation abilities, the endogenous IAA content in the leaves could was reduced under low temperature stress, promoted the production of 5-HT, improved the contents of photosynthetic pigments, GA, and ABA, as well as enhanced photosynthetic carbon assimilation abilities, which would increase photosynthesis in the K. obovata seedlings. Under cold acclimation conditions, the spraying of p-CPA could significantly inhibit the synthesis of 5-HT, promote the production of IAA, and reduce the contents of photosynthetic pigments, GA, ABA, and CE, which would weaken the effects of cold acclimation by improving the cold resistance of mangroves. In conclusion, cold acclimation could improve the cold resistance abilities of K. obovata seedlings by regulating photosynthetic carbon assimilation capacity and the contents of endogenous phytohormone. 5-HT synthesis is one of the necessary conditions for improving the cold resistance abilities of mangroves.
5-羟色胺(5-HT)不仅能参与植物的生长发育,还可以延缓衰老及应对非生物胁迫。为探明5-HT在调控红树林抗寒中的作用,以红树植物秋茄为试验材料,研究抗寒锻炼和喷施DL-4-氯苯丙氨酸(p-CPA, 5-HT合成抑制剂)对低温胁迫下秋茄幼苗叶片气体交换参数、CO2响应曲线(A/Ca)和内源植物激素含量的影响。结果表明: 低温胁迫显著降低了秋茄幼苗叶片5-HT、叶绿素、内源生长素(IAA)、赤霉素(GA)和脱落酸(ABA)含量,减弱了其利用CO2的能力,降低了净光合速率,抑制了初始羧化效率。低温胁迫下施用外源p-CPA降低了秋茄幼苗叶片光合色素、内源各激素和5-HT含量,加剧了低温胁迫对秋茄幼苗叶片光合功能的伤害。抗寒锻炼可有效降低低温胁迫下秋茄幼苗叶片内源IAA含量,促使植株产生更多的5-HT,提高了叶片光合色素、GA、ABA含量和初始羧化效率,提升了光合碳同化能力,最终提高了秋茄幼苗叶片的光合作用;抗寒锻炼下喷施p-CPA会显著抑制秋茄幼苗叶片5-HT合成,促进IAA产生,同时降低光合色素、GA、ABA含量和初始羧化效率,减弱抗寒锻炼对红树林抗寒性的提高作用。综上所述,抗寒锻炼通过调控光合碳同化能力和内源植物激素含量提高秋茄幼苗的抗寒性,5-HT的合成是提高红树林抗寒性的必要条件之一。.
Keywords: 5-HT; CO 2 response curve; cold acclimation; endogenous phytohormone; low temperature stress; mangrove; photosynthesis.