CAJ | 학술논문

【目的】作物选择性吸收铵态氮或硝态氮是导致根际pH发生变化的主要原因,本文探索旱地作物根系细胞膜质子泵对铵硝营养及pH的反应机制。【方法】采用水培方法,分别用NH+4-N和NO-3-N培养高粱幼苗,并控制营养液的pH。高粱生长三周以后,用葡聚糖两相法分离根系细胞膜,测定细胞膜质子泵的水解活性、酶动力学特征,利用免疫杂交方法测定质子泵蛋白浓度。【结果】培养三周后,供给铵态氮的高粱根际pH下降到3,质子泵活性最高,达到Pi 8．81μmol/(mg·min)；供给硝态氮的高粱根际pH上升至7,质子泵活性最低,为Pi 3．82μmol/(mg· min)。将铵态氮处理的营养液pH人为上调到7,而将硝态氮处理下调到3后发现,铵态氮培养的高粱根系细胞膜质子泵活性在pH 7时低于pH 3,但仍高于pH 3时硝态氮处理。酶动力学特征的测定结果表明,铵态氮营养( pH 3)时,酶反应最大速率最高,亲和性也最高,而硝态氮营养(pH 7)时酶反应最大速率最小,亲和性也最低。质子泵活性与其蛋白浓度之间具有正相关性。【结论】无论是铵还是硝态氮处理,根际pH降低都会导致高粱根系细胞膜质子泵活性升高,这说明,质子泵具有适应根际酸化而提高自身活性的基本功能。但是,在相同的pH下,铵态氮都导致高粱根系细胞膜质子泵活性比硝态氮处理更高,这说明铵态氮在根系细胞中同化产生氢离子,而硝态氮的还原不产生氢离子,因此,吸收铵态氮的细胞需要进一步提高细胞膜质子泵的活性将氢离子排出体外。这很可能是高粱根系在铵态氮营养下的一种反应机制。
【목적】작물선택성흡수안태담혹초태담시도치근제pH발생변화적주요원인,본문탐색한지작물근계세포막질자빙대안초영양급pH적반응궤제。【방법】채용수배방법,분별용NH+4-N화NO-3-N배양고량유묘,병공제영양액적pH。고량생장삼주이후,용포취당량상법분리근계세포막,측정세포막질자빙적수해활성、매동역학특정,이용면역잡교방법측정질자빙단백농도。【결과】배양삼주후,공급안태담적고량근제pH하강도3,질자빙활성최고,체도Pi 8．81μmol/(mg·min)；공급초태담적고량근제pH상승지7,질자빙활성최저,위Pi 3．82μmol/(mg· min)。장안태담처리적영양액pH인위상조도7,이장초태담처리하조도3후발현,안태담배양적고량근계세포막질자빙활성재pH 7시저우pH 3,단잉고우pH 3시초태담처리。매동역학특정적측정결과표명,안태담영양( pH 3)시,매반응최대속솔최고,친화성야최고,이초태담영양(pH 7)시매반응최대속솔최소,친화성야최저。질자빙활성여기단백농도지간구유정상관성。【결론】무론시안환시초태담처리,근제pH강저도회도치고량근계세포막질자빙활성승고,저설명,질자빙구유괄응근제산화이제고자신활성적기본공능。단시,재상동적pH하,안태담도도치고량근계세포막질자빙활성비초태담처리경고,저설명안태담재근계세포중동화산생경리자,이초태담적환원불산생경리자,인차,흡수안태담적세포수요진일보제고세포막질자빙적활성장경리자배출체외。저흔가능시고량근계재안태담영양하적일충반응궤제。
[Objectives]Ammonium and nitrate nutrition strongly affect the rhizosphere pH. The response of upland crop to the different pH in root with ammonium and nitrate supplies was studied. [Methods] Using a hydroponic experiment, sorghum( Sorghum bicolor) was supplied with NH+4-N or NO-3-N as sole nitrogen nutrition. After 3 weeks’ cultivation, the plasma membrane vesicles of sorghum roots were isolated using a two-phase system with poly-glucose. The rhizosphere pH and the plasma membrane H+-ATPase hydrolytic activity were measured, and the enzyme concentration was tested by immune hybridizes.[Results] The activity of H+-ATPase in the plasma membrane of sorghum roots supplied with NH+4-N(pH3)is 8. 81 μmol Pi/(mg·min)and is markedly higher than that supplied with NO-3-N(pH 7)(3. 82 μmol Pi/(mg·min). If the pH was adjusted to 7 in the medium with ammonium nutrition, the activity of H+-ATPase is decreased. In contrast, if the pH was adjusted to 3 in the medium with nitrate nutrition, the activity of H+-ATPase is increased, and the activity of H+-ATPase in sorghum roots treated by ammonium nutrition related to the protein concentration. These results indicate that the higher activity of plasma membrane H+-ATPase in sorghum roots is affected by the rhizosphere pH. However, ammonium has stronger influence on the activity of plasma membrane H+-ATPase, even at the same medium pH.[Conclusion]Plasma membrane H+-ATPase could adapt to the rhizosphere acidification by enhancing its activity, either under ammonium or nitrate application. In contrast to the H+ consumption after nitrate reduction, the H+production after ammonium assimilation should be pumped outside the root cell with further enhancement of the plasma membrane H+-ATPase activity. This might be the mechanism of adaptation to ammonium nutrient by sorghum roots.