纯化腐植酸对氮胁迫下黄瓜幼苗生长和氮代谢的影响

为研究纯化腐植酸(PHA)在不同水平氮胁迫下对黄瓜植株生长和氮代谢的影响,探明PHA对逆境胁迫的缓解作用机制,采用水培方式,选用新泰密刺为供试品种,以正常氮水平(11 mmol·L^-1 NO₃^-)为对照,进行低氮(1.0 mmol·L^-1 NO₃^-)和高氮(101 mmol·L^-1 NO₃^-)胁迫处理,研究纯化腐植酸对氮胁迫下黄瓜幼苗生长和氮代谢的影响.结果表明: 低氮和高氮胁迫均抑制了黄瓜幼苗生长,株高、茎粗、叶面积、干物质积累量均低于正常氮水平处理.施用纯化腐植酸促进了正常氮水平及低氮胁迫下黄瓜干物质积累,在高氮胁迫下差异不显著.PHA影响了黄瓜幼苗NO₃^-的吸收,呈低氮下促进、高氮下抑制吸收的趋势;PHA显著降低了低氮、高氮胁迫下根系和叶片中的铵态氮含量;与正常氮水平相比,低氮、高氮胁迫下根系和叶片的硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)、谷氨酸脱氢酶(GDH)活性及根系中亚硝酸还原酶(NiR)活性均显著降低,PHA不同程度地提高了NR、NiR、GS、GOGAT、GDH活性,还提高了根系和叶片中游离氨基酸、可溶性蛋白的含量.综上,添加PHA缓解了氮胁迫对黄瓜幼苗生长的抑制作用.

Effects of purified humic acid on the growth and nitrogen metabolism of cucumber seedlings under nitrogen stress.

To investigate the effects of purified humic acid (PHA) on the growth and nitrogen metabolism of cucumber under different levels of nitrogen stress and to explore the mechanism of PHA’s alleviation on abiotic stress, we examined the effects of PHA on ‘Xintaimici’ cucumber growth and nitrogen metabolism under low nitrogen (1.0 mmol·L^-1 NO₃^-) stress and high nitrogen (101 mmol·L^-1 NO₃^-) stress in hydroponics compared with normal level (11 mmol·L^-1 NO₃^-). The results showed that the growth of cucumber seedlings was inhibited under nitrogen stress treatments. Plant height, stem diameter, leaf area and dry matter accumulation under nitrogen stress were lower than that at normal nitrogen level. Dry matter accumulation under the normal nitrogen level and low nitrogen stress were significantly increased by PHA, but there was no significant difference under high nitrogen stress. The absorption of NO₃^- in cucumber seedlings was affected by PHA, showing increased nitrate content in cucumber seedlings under low nitrogen stress and decreased under high nitrogen stress. PHA significantly decreased ammonium content in roots and leaves under low and high nitrogen stress. Compared with normal level of nitrogen (CK), NR, GS, GOGAT, GDH activity in roots and leaves and NiR activity in roots significantly decreased under low and high nitrogen stress. PHA increased the activities of NR, NiR, GS, GOGAT, and GDH to different extents. PHA increased amino acid and soluble protein content in cucumber seedling roots and leaves. In summary, PHA addition alleviated the inhibitory effect of nitrogen stress on the growth of cucumber seedlings.