【作者】 葛体达； 黄丹枫； 宋世威； 姜武；

【机构】 上海交通大学农业与生物学院；

【摘要】 近来越来越多研究表明,许多植物能够在不经矿化的情况下直接吸收、利用环境介质中的有机态N,尤其是氨基酸态N。而且,有些植物利用氨基酸的能力与矿质氮源（NH₄⁺-N、NO₃^--N）相当甚至更高。为研究有机氮对番茄N营养的贡献率以及不同番茄品种对有机态N吸收利用能力的差异,选用两个不同番茄品种（申粉918、沪樱932）,土培条件下利用¹⁵NH₄Cl、K¹⁵NO₃、¹³C,¹⁵N标记同位素稀释法技术,通过质谱分析,测定了不同形态的¹⁵N注射48h后,番茄幼苗根系、地上部的¹³C、¹⁵N原子超以及¹³C和¹⁵N原子超之间的相关关系。结果表明,两个番茄品种的地上部、根系¹⁵N原子超均表现为¹⁵N-KNO₃>¹⁵N-NH₄Cl>2-[¹³C],[¹⁵N]- glycine>CK处理,表明番茄是喜硝作物。不同氮素形态处理下,两个番茄品种根系¹⁵N平均原子超显著大于地上部的¹⁵N平均原子超（P<0.05）。不同形态的¹⁵N注射48h后,相对于对照、¹⁵N-NH₄Cl和¹⁵N-KNO₃三个处理来说,供以2-[¹³C],[¹⁵N]-glycine时,两个番茄品种的地上部、根系¹³C、¹⁵N原子超均显著提高,且根系¹³C原子超显著大于地上部。通过番茄根系¹³C、¹⁵N回归方程斜率和2-[¹³C],[¹⁵N]-glycine中¹³C:¹⁵N的比值推测中粉918、沪樱932从土壤中吸收的氮分别有12.5%和21%是以完整的甘氨酸分子直接吸收的。方差分析结果表明,甘氨酸态N对沪樱932的氮营养贡献率显著大于申粉918（P<0.05）。本研究还表明,植物和微生物对土壤有机氮态N（尤其是氨基酸态N）营养存在相互竞争。在本试验条件下,番茄根系吸收甘氨酸态N的能力比土壤微生物弱。综上,番茄具有直接吸收利用整个分子的氨基酸态N的能力,其吸收能力因品种而异。更多还原

【Abstract】 Organic nitrogen （ON） compounds uptake directly,rather than solely inorganic N by plant roots has been hypothesized to constitute a significant pathway for plant nutrition particularly in N limiting ecosystems.The aim of this study was to test whether tomato （Solanum lycopersicum） can take up organic nitrogen directly from the soil and whether different genotypes differ in this respect by using ¹⁵NH₄Cl,K¹⁵NO₃,2-[¹³C],[¹⁵N]-glycine labeling techniques.We selected two genotypes of tomato （cv."Shengfen-918"and cv."Huying-932"） by using plants growing in"rhizotube"（microcosms） with natural field soil.The results showed that significant increases in ¹³C and ¹⁵N in plants （shoots and roots）,indicating part of the glycine N was taken up in the form of intact amino acid by two cultivars tomato 48 h after injection.Regression analysis of excess ¹³C against excess ¹⁵N showed that about 12.5% and 21% of glycine-N was taken up intact by"Shengfen 918"and"Huying932"respectively,possible losses of labeled C atoms of glycine during its metabolism in the plants implies that these estimates are conservative.Uptake of the different N sources was similar in both"Shengfen 918"and"Huying932",while the rates of glycine uptake of"Huying932"were significantly higher than that of"Shengfen 918".48 h after ¹⁵N injection,atom% excess ¹⁵N and ¹³C in the roots was higher than that in any of the shoots.Results also indicated that the rapid turnover of amino acids （e.g.glycine） by soil microorganisms,and the poor competitive ability of tomato roots to absorb amino acids from the soil solution.This implies that tomato can take up organic nitrogen in intact form from the soil,despite the rapid turnover of organic N usually found under such conditions,and also uptake capacity varies widely among genotype dependent.The dependence of agricultural plants on nitrate and ammonium as the only forms of available N is therefore questionable.Further studies investigating the functional ecological implications of ON in horticultural ecosystems given the influence of climatic change and N pollution is therefore warranted.更多还原