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首页> 外文期刊>Journal of Plant Physiology >Integrated operation of the photorespiratory cycle and cytosolic metabolism in the modulation of primary nitrogen assimilation and export of organic N-transport compounds from leaves: A hypothesis
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Integrated operation of the photorespiratory cycle and cytosolic metabolism in the modulation of primary nitrogen assimilation and export of organic N-transport compounds from leaves: A hypothesis

机译：光呼吸循环和胞质代谢的综合操作，调节初级氮同化和叶片中有机N转运化合物的输出：一个假设

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Photorespiration is generally considered to be an essentially dissipative process, although it performs some protective and essential functions. A theoretical appraisal indicates that the loss of freshly assimilated CO2 due to photorespiration in well-watered plants may not be as high as generally believed. Even under moderately adverse conditions, these losses may not exceed 10%. The photorespiratory metabolism of the source leaves of well-watered and well-nourished crop plants ought to be different from that of other leaves because the fluxes of the export of both carbohydrates and organic N-transport compounds in source leaves is quite high. With a heuristic approach that involved the dovetailing of certain metabolic steps with the photorespiratory cycle (PR-cycle), a novel network is proposed to operatein the sourceleaves of well-watered and well-nourished plants. This network allows for the diversion of metabolites from their cyclic-routes in sizeable quantities. With the removal of considerable quantities of glycine and serine from the cyclic route, the number of RuBP oxygenation events would be several times those of the formation of hydroxypyruvate. Thus, to an extreme extent, photorespiratory metabolism would become open-ended and involve much less futile recycling of glycine and serine. Conversion of glyoxylate to glycine has been proposed to be a crucial step in the determination of the relative rates of the futile (cyclic) and anabolic (open-ended) routes. Thus, in the source leaves of well-watered and well-nourished plants, the importance of the cyclic route is limited to the salvaging of photorespiratory intermediates for the regeneration of RuBP. The proposed network is resilient enough to coordinate the rates of the assimilation of carbon and nitrogen in accordance with the moisture and N-fertility statuses of the soil
机译：光呼吸虽然被认为具有一定的保护和基本功能，但通常被认为是一个耗散的过程。理论上的评估表明，在水分充足的植物中，由于光呼吸而导致的新鲜吸收的二氧化碳损失可能不如一般人认为的那么高。即使在中等不利条件下，这些损失也不得超过10％。水分充足和营养良好的作物植物的源叶的光呼吸代谢应该与其他叶的不同，因为源叶中碳水化合物和有机氮转运化合物的出口通量都很高。通过一种启发式方法，其中涉及将某些代谢步骤与光呼吸循环（PR循环）结合在一起，提出了一种新颖的网络来在水分充足和营养丰富的植物的源叶中运行。该网络允许大量代谢物从其循环路径转移。随着从循环途径中去除大量的甘氨酸和丝氨酸，RuBP氧化事件的次数将是羟基丙酮酸盐形成的几倍。因此，在最大程度上，光呼吸代谢将成为开放式的，并且涉及的甘氨酸和丝氨酸的循环利用将大大减少。已经提出乙醛酸酯向甘氨酸的转化是确定无效（环状）和合成代谢（开放式）途径的相对速率的关键步骤。因此，在水份充足和营养丰富的植物的源叶中，循环途径的重要性仅限于挽救光呼吸中间产物以再生RuBP。拟议的网络具有足够的弹性，可以根据土壤的水分和氮肥状况协调碳和氮的吸收速率

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