瓜尔豆发育过程中碳水化合物含量的变化

研究了瓜尔豆生长发育过程中叶片、种荚及籽粒中蔗糖合成酶（SS）和蔗糖磷酸合成酶（SPS）活性的变化、糖类物质的组成及其含量的动态变化，以揭示可溶性糖的合成对瓜尔豆胚乳中半乳甘露聚糖和淀粉积累的影响。结果表明，进入开花期（播种后45 d）后，叶片、种荚和籽粒中SS和SPS活性均呈降低趋势。籽粒中的SS和SPS活性呈正相关，且显著高于叶片和种荚中相应酶活性。叶片中葡萄糖（Glc）含量高于蔗糖（Suc）。种荚中可溶性糖含量与Suc含量均呈单峰曲线，在籽粒直径5 mm时达峰值，两者呈正相关。Suc是种荚中暂存含量最多的可溶性糖，但其含量与SS和SPS活性无显著相关性，它主要来自叶片。种荚中Suc含量与籽粒碳水化合物总量（可溶性糖+多糖）呈负相关，它是籽粒碳水化合物合成的重要物质来源，还与籽粒库的建成有关。随种子发育，籽粒可溶性糖含量呈逐步下降趋势。籽粒发育前期，叶片同化物以Suc的形式运输并大量积累在种荚中，当籽粒直径达5 mm后迅速由种荚卸载至籽粒。但卸载期籽粒Suc含量较低，且显著低于种荚，说明籽粒Suc迅速转化为其他可溶性糖，并进一步用于多糖合成。籽粒直径为4 mm至5 mm时是种荚由“源”到“库”转换的临界期，这时籽粒中淀粉积累较迅速，半乳甘露聚糖在籽粒直径达5 mm后进入迅速积累期。

Changes in Carbohydrate Contents during Guar Plant Development

Guar Cyamposis Tetragonoloba(L.) Taub.] is an important raw material for guar gum,in which galactomannan(GM) is the active component.GM is a main storage carbohydrate in guar seeds,which is an analogue to that of starch in cereal grains.Sucrose is a common precursor for the biosynthesis of GM and starch.Studies were made on the changes in sucrose synthetic enzymes and carbohydrate contents in guar plants,to understand the effect of soluble sugar biosynthesis on accumulation of endospermic polysaccharides in this special plant.Sucrose synthetase(SS) and sucrose phosphate synthetase(SPS) activities,compositions and contents of carbohydrates in guar leaves,seeds,and pod peels were determined.The results showed that SS and SPS activities in leaves,pod peels,and seeds decreased with the development of seeds.SS and SPS activities in the seeds were higher than those in leaves and pod peels.SS activity showed a positive correlation with SPS activity in seeds.Glucose content was significantly higher than sucrose content in leaves.Contents of soluble sugar and sucrose increased in pod peels,till the diameter of seed was about 5 mm,and then decreased quickly,they were well correlated with each other.Soluble sugar of seeds decreased gradually during seed development.Sucrose content in pod peels showed a negative correlation with total carbohydrate contents(soluble sugar polysaccharides) in seeds,and it is an important source of the carbohydrate in the seeds.It took part in the carbohydrate synthesis and also the establishment of seed sink.Carbohydrates in the leaves,as sucrose transported to and temporarily deposited in the pod peels in the early period of seed development,and then transported rapidly from pod peels into seeds at the seed diameter of about 5 mm.However,there was less sucrose in seeds than in pod peels,it suggested that sucrose was inverted into other reduced sugars after transported into seeds.Starch accumulated quickly in the seeds when the seed diameter was about 4 to 5 mm,a critical period for pod peels changing from `sink' to `source',and galactomannan increased dramatically in the seeds after that.