Growth and composition of maize kernels cultured in vitro with varying supplies of carbon and nitrogen.
Growth and composition of maize kernels cultured in vitro with varying supplies of carbon and nitrogen.
复制标题
不同碳和氮供应下体外培养的玉米粒的生长和组成。
作者：
G. W. Singletary;F. Below
本研究采用离体种子培养方法，研究了碳氮供应对玉米生长（即淀粉积累）和蛋白质组成的影响。胚乳未成熟的籽粒在含有不同浓度的C（蔗糖，234毫摩尔[低]和468毫摩尔[高]）和N（氨基酸混合物，N为0至144毫摩尔）的液体培养基上生长至成熟。低碳限制淀粉的积累，但不提供氮，胚乳。随着供氮量从0增加到13.4毫摩尔，高C，胚乳淀粉和蛋白质含量随之增加。胚乳生长不受额外的N，直到浓度超过约72毫摩尔减少淀粉积累。当籽粒生长在低碳条件下时，低氮浓度对淀粉沉积也有类似的抑制作用。胚乳总氮含量达到饱和点，约36毫摩尔的N在介质中，无论C供应。玉米醇溶蛋白在胚乳中的合成在所有的N水平的积极响应，而谷蛋白含量保持不变，白蛋白/球蛋白的量减少时，N供应大于36毫摩尔。在成熟胚乳组织中观察到游离氨基酸和可溶性糖的浓度之间的倒数，反比关系。我们的数据表明，在氮胁迫下，淀粉和蛋白质积累在胚乳中是相互依赖的，至少在外观上，但在其他方面是独立的。
This study employed in vitro seed culture to determine how C and N supply influence the growth (i.e. starch accumulation) and protein composition of maize (Zea mays L.) endosperm. Immature kernels were grown to maturity on liquid medium containing various concentrations of C (sucrose at 234 millimolar [low] and 468 millimolar [high]) and N (amino acid mixture ranging in N from 0 to 144 millimolar). Low C supply limited starch, but not N, accumulation in the endosperm. With high C, endosperm starch and protein content increased concomitantly as N supply increased from 0 to 13.4 millimolar. Endosperm growth was unaffected by additional N until concentrations exceeding approximately 72 millimolar reduced starch accumulation. A similar inhibition of starch deposition occurred with lower N concentrations when kernels were grown with low C. Endosperm total N content reached a point of saturation with approximately 36 millimolar N in the medium, regardless of C supply. Zein synthesis in the endosperm responded positively across all N levels, while glutelin content remained static and albumin/globulin proteins were reduced in amount when N supply was greater than 36 millimolar. A reciprocal, inverse relationship was observed in mature endosperm tissue between the concentrations of free amino acids and soluble sugars. Our data suggest that under N stress starch and protein accumulation in the endosperm are interdependent, at least in appearance, but are independent otherwise.