马齿苋中草酸钙晶体形态及积累特征

马齿苋(Portulaca oleracea L.)是营养价值较高的常用野生蔬菜,含有丰富的矿质元素,但目前人们对其钙养分的存在状态还缺乏认识,因此本研究对马齿苋茎和叶进行了显微观察,以了解马齿苋是否含有固定钙的草酸钙晶体以及晶体的积累特征。结果表明,马齿苋积累的草酸钙晶体,属于簇晶类型,直径为25~50μm;分布于茎的髓部和叶的叶肉组织中,叶中晶体多,每1 mm²叶片约含有287个晶体,而茎中含晶体少,每1 mm²茎横切面上只含有26多个晶体。叶中的草酸总含量、可溶性草酸和不溶性草酸含量均高于茎中,草酸分布模式与草酸钙晶体分布模式一致。显然,由于草酸钙晶体的积累,马齿苋中的钙相当一部分以难溶状态存在。

Crystal Morphology and Accumulation Characteristics of Calcium Oxalate in Portulaca oleracea

Portulaca oleracea is commonly used as wild vegetable with high nutritional value.It is rich in mineral elements,but the existing forms of calcium are not well understood.In this study,the stem and leaf of P.oleracea were observed microscopically to understand whether there were calcium oxalate crystals with fixed calcium in P.oleracea and the characteristics of crystal accumulation.The results showed that P.oleracea accumulated calcium oxalate crystals,which belonged to cluster crystal type with diameter of 25-50μm.The crystal in leaves and pulp tissues of stem and leaf was more(280 mm²),but less in stem(20 mm²).The contents of total oxalate acid,soluble oxalate acid and insoluble oxalic acid in leaves were higher than those in stems.The distribution pattern of oxalic acid is consistent with that of calcium oxalate crystal. Obviously, a considerable portion of calcium in purslane exists in a insoluble form, as a result of the accumulation of calcium oxalate crystals.