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液泡大量贮存的NO3--N不能及时转入细胞质还原再利用,是造成植物大量累积NO3--N和阻碍氮素利用效率进一步提高的主要原因。本文阐述了液泡膜上NO3--N的转运机制,在液泡膜上存在着两种功能和物理特性完全不同的质子泵,即H+-ATPase和H+-PPase,这两个质子泵分别以Mg·ATP和Mg·PPi为底物,水解得到的H+被泵进液泡中,从而造成细胞质与液泡之间的H+电化学梯度,而后者在很大程度上决定着硝酸盐从液泡中外流至细胞质中的过程,硝酸盐从细胞质进入液泡主要靠液泡膜上的H+/NO3-反运门(antiport)来完成,而液泡膜上硝酸盐与其他阴离子构成的共运门(symport)则有利于液泡中的硝酸盐向细胞质转移。液泡膜质子泵对NO3--N的转运还受到细胞质硝酸还原酶(NR)活性的影响,细胞质NR可以不断同化还原NO3--N,从而使储存于液泡的NO3--N更多地转运到细胞质加以利用。这些都将为进一步研究有效、可行的氮素利用措施,提高NO3--N再利用效率提供参考。
The large amount of NO3 - N stored in vacuole can not be transferred to the cytoplasm for re - use in time, which is the main reason for the large accumulation of NO3 - N in plants and hindering the further improvement of nitrogen use efficiency. This paper describes the transport mechanism of NO3 - N on tonoplast. There are two kinds of proton pumps with completely different functions and physical properties on the tonoplast: H + -ATPase and H + -PPase, ATP and Mg · PPi as substrates, the hydrolyzed H + is pumped into the vacuole, resulting in an H + electrochemical gradient between the cytoplasm and the vacuole, which largely determines the outflow of nitrate from the vacuole into the cytoplasm , The entry of nitrate from the cytoplasm into the vacuole mainly depends on the H + / NO3- antiport from the vacuolar membrane, while the symport formed by the nitrate and other anions on the tonoplast is favorable to the vacuole Of nitrate to the cytoplasm transfer. The transport of NO3 - N by tonoplast proton pump was also affected by the activity of cytoplasmic nitrate reductase (NR), and the cytoplasmic NR could assimilate NO3 - N to assimilate the NO3 - N stored in the vacuole to Cytoplasm to be used. All of these will provide reference for further study of effective and feasible nitrogen utilization measures and improvement of NO3 - N recycle efficiency.