草地早熟禾氮代谢及与根茎扩展的相关性研究

Study on the changes of nitrogen metabolism and its correlation with rhizome expansion of Poa pratensis

摘要:

为明确草地早熟禾(Poa pratensis)含氮化合物在不同生育时期的变化规律及与根茎扩展的关系，对根茎扩展能力存在显著差异的 3 个野生草地早熟禾材料(LZYZ、DXWY 和 DXAD)不同生育时期根茎扩展及氮代谢相关指标进行测定。结果表明，草地早熟禾根茎扩展主要集中在返青期至抽穗期，该阶段 LZYZ、DXWY 和 DXAD 分蘖数分别增加 176. 08%、127. 13% 和 65. 90%；根茎数分别增加 662. 14%、544. 94% 和 429. 41%。拔节期至抽穗期是地上生物量快速积累阶段，该阶段 3 个材料地上生物量绝对增长率分别为 136. 22、78. 71、68. 33 g/(株·d)；根茎生物量有两个快速积累时期，拔节期至抽穗期 3 个材料根茎生物量绝对增长率分别为 26. 33、13. 48、4. 42 g/(株·d)；成熟期至枯黄期，3 个材料分别为 45. 39、35. 11、16. 26 g/(株·d)。硝态氮(NO₃ ^- ‐N)含量与硝酸还原酶(NR)活性随生育时期推进呈单峰曲线变化，峰值分别出现在拔节期和抽穗期；游离氨基酸含量呈“升‐降‐升”的变化规律，峰值出现在抽穗期，在枯黄期有所上升；谷氨酰胺合成酶(GS)和谷氨酸合成酶(GOGAT)活性均呈双峰曲线变化，峰值出现时期分别为抽穗期和成熟期；谷氨酸脱氢酶(GDH)活性生长前期较低，开花期迅速上升，在成熟期达最大值，枯黄期仍保持较高活性。相关性分析显示，草地早熟禾根茎扩展各指标增长率与 NO₃ ^-‐N、游离氨基酸、NR、GS 和 GOGAT 极显著或显著正相关，与 GDH 活性负相关。因此，草地早熟禾根茎中硝态氮和游离氨基酸含量越多，NR、GS 和 GOGAT 活性越高、GDH 活性越低，越有利于根茎扩展。

Abstract:

In order to determine the dynamic changes of nitrogen compounds in Poa pratensis with different growth stages and its relationship with rhizome expansion，three wild Poa pratensis with significant differences in rhi‐ zome expansion ability were used as materials to measure the indexes of rhizome expansion and nitrogen metabolism at different growth stages. The results showed that the rhizoid expansion of Poa pratensis mainly occurred from re‐ greening stage to heading stage，during which the tiller numbers of LZYZ，DXWY and DXAD increased by 176. 08%，127. 13% and 65. 90%，respectively and the number of rhizomes increased by 662. 14%，544. 94% and 429. 41%，respectively. The results also implied that the aboveground biomass accumulated rapidly from jointing stage to heading stage，and the absolute aboveground biomass growth rates of the three materials were 136. 22， 78. 71 and 68. 33 g/(plant ? d)，respectively. There were two rapid accumulation periods of rhizome biomass. One was from jointing stage to heading stage，in which the absolute growth rates of rhizome biomass of the three materials were 26. 33，13. 48 and 4. 42 g/(plant ? d). The other was from mature stage to withering stage，in which the abso‐ lute growth rates of the three materials at this stage were 45. 39，35. 11 and 16. 26 g/(plant ? d)respectively. The re‐ sults further indicated that nitrate nitrogen(NO₃ ^- ‐N)content and nitrate reductase(NR)activity showed a single peak curve with the growth stage，and the peaks appeared at jointing stage and heading stage，respectively. The con‐ tent of free amino acids showed a "rise‐decline‐rise" pattern，with the peak appearing in heading stage and increasing in withering stage. The activities of glutamine synthase(GS)and glutamate synthase(GOGAT)showed a double‐ peak curve，and the peaks were at heading stage and maturity stage，respectively. The activity of glutamate dehydro‐ genase(GDH)was low in early growth stage，increased rapidly from flowering stage to maturity stage，reached the the maximum in the mature stage，and remained high in withering stage. Correlation analysis showed that the growth rates of each index of Poa pratensis rhizome expansion were significantly or positively correlated with NO₃ ^- ‐N，free amino acids，NR，GS and GOGAT，and negatively correlated with GDH activity. Therefore，the higher the nitrate nitrogen and free amino acid contents in the rhizome of Poa pratensis，the higher the activities of NR，GS and GOGAT，the lower the activities of GDH，and the more conducive to the rhizome expansion. The results of this study provide a theoretical basis for the regulation mechanism of rhizome expansion and rational fertilization of Poa pratensis.