籽粒苋不同富钾基因型根系分泌物中有机酸和氨基酸的变化特点

采用溶液培养试验研究了籽粒苋(Amaranthus.spp.)不同富钾基因型在不同供钾水平条件下3个不同生长时期内根系分泌物中氨基酸和有机酸的种类及含量变化情况。结果表明,1)籽粒苋根系分泌物中氨基酸和有机酸含量随着供钾水平的升高而降低,且富钾基因型始终大于一般基因型。在低钾胁迫时,根系分泌物中有10种氨基酸和5种有机酸出现,而在供钾正常时则缺少谷氨酸、甘氨酸、苯丙氨酸、草酸和柠檬酸等;酪氨酸、-氨基丁酸和丝氨酸的含量约占氨基酸分泌总量的一半以上;苹果酸含量约占有机酸分泌总量的60%以上。2)籽粒苋生长50d时,一般基因型氨基酸和有机酸的分泌总量较生长40d时迅速降低,而富钾基因型降低速度则相对较为平稳。在3个生长期内,酪氨酸、-氨基丁酸和丝氨酸均为两类基因型根系分泌物中的主要氨基酸种类,苹果酸则是主要的有机酸类型,其在氨基酸和有机酸分泌总量中所占相对比例均随生长期的延长而升高。3)籽粒苋根系分泌物处理后的土壤速效钾含量均高于清水对照处理,富钾基因型在低钾胁迫时的根系分泌物对土壤钾的活化作用明显大于一般基因型。

Change characteristics of organic acid and amino acid in root exudates in different grain amaranth genotypes

The type and variation scenario of organic acid and amino acid in root exudates of different grain amaranth genotypes were studied under three levels of potassium supplication conditions at 3 development durations. The result shows: 1) The root exudation rates of amino acids and organic acids would decrease along with the rise of potassium supply level, meanwhile, amino acid and organic acids in root exudates of potassium-rich genotypes was always higher than that of common one. Under potassium stress condition, eleven kinds of amino acids and five kinds organic acids were found in root exudates, while glutamic, glycin, phenylalanine, oxalic acid and citric acid were missed under normal potassium supply conditon. Tyrosine, serine and γ-amidobutyricacid account for more than 50% of total exudates. While malic acid accouted for over 60% of total organic acid, which was the dominant one. 2) Compared with development stage at the fortith day, total exudation rates of amino acids and organic acids in common genotype at the fifith day decreased sharply, while it kept rather stationary in potassium-rich genotype; At three growth phrases, tyrosine, serine and γ-amidobutyricacid were dominant amino acids in root exudates of those two genotypes, malic acid was dominant organic acids, and the proportision of malic acid to total exudation increased with the prolongation of growth phase prolonged. 3) The content of available potassium treated with root exudates was markedly higher than control treanted by pure water treatment, and root excudates of potassium-rich genotype could activate potassiun in soil more than that of common genotype under potassium stress condition.