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首页> 外文期刊>Journal of Plant Physiology >Nitrogen metabolism in leaves of a tank epiphytic bromeliad: characterization of a spatial and functional division.
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Nitrogen metabolism in leaves of a tank epiphytic bromeliad: characterization of a spatial and functional division.

机译：罐附生凤梨叶中的氮代谢：空间和功能分区的表征。

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The leaf is considered the most important vegetative organ of tank epiphytic bromeliads due to its ability to absorb and assimilate nutrients. However, little is known about the physiological characteristics of nutrient uptake and assimilation. In order to better understand the mechanisms utilized by some tank epiphytic bromeliads to optimize the nitrogen acquisition and assimilation, a study was proposed to verify the existence of a differential capacity to assimilate nitrogen in different leaf portions. The experiments were conducted using young plants of Vriesea gigantea. A nutrient solution containing NO3-/NH4+ or urea as the sole nitrogen source was supplied to the tank of these plants and the activities of urease, nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (NADH-GDH) were quantified in apical and basal leaf portions after 1, 3, 6, 9, 12, 24 and 48 h. The endogenous ammonium and urea contents were also analyzed. Independent of the nitrogen sources utilized, NR and urease activities were higher in the basal portions of leaves in all the period analyzed. On the contrary, GS and GDH activities were higher in apical part. It was also observed that the endogenous ammonium and urea had the highest contents detected in the basal region. These results suggest that the basal portion was preferentially involved in nitrate reduction and urea hydrolysis, while the apical region could be the main area responsible for ammonium assimilation through the action of GS and GDH activities. Moreover, it was possible to infer that ammonium may be transported from the base, to the apex of the leaves. In conclusion, it was suggested that a spatial and functional division in nitrogen absorption and NH4+ assimilation between basal and apical leaf areas exists, ensuring that the majority of nitrogen available inside the tank is quickly used by bromeliad's leaves.
机译：由于其吸收和吸收养分的能力，叶子被认为是箱附生凤梨科植物的最重要的营养器官。但是，对养分吸收和吸收的生理特性知之甚少。为了更好地理解一些罐附生凤梨科植物利用其优化氮素吸收和同化的机制，提出了一项研究，以验证不同叶片部分存在的同化氮的差异能力。该实验是使用大花紫薇的年轻植物进行的。将含有NO 3 - / NH 4 + 或尿素作为唯一氮源的营养液供应给在1、3、6、9、12、24和12、3和6的顶端和基部叶片中定量尿素酶，硝酸还原酶（NR），谷氨酰胺合成酶（GS）和谷氨酸脱氢酶（NADH-GDH）的活性。 48小时还分析了内源性铵和尿素的含量。与所使用的氮源无关，在所分析的所有时期中，叶片基部的NR和脲酶活性较高。相反，GS和GDH活性在根尖较高。还观察到，内源性铵和尿素在基部区域的含量最高。这些结果表明，基部优先参与硝酸​​盐的还原和尿素的水解，而顶部区域可能是通过GS和GDH活性作用而引起铵同化的主要区域。而且，有可能推断出铵可能从碱转运到叶的顶端。总之，建议在基部和根部叶区域之间存在氮吸收和NH 4 + 同化的空间和功能划分，从而确保内部的大部分氮素可用该罐可被凤梨叶迅速使用。

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