Abstract:

In order to clear indole acetic acid (IAA) secreting ability of endophytic bacteria and their distribution from forage on alpine grassland in the special environment. Endophytic bacteria were isolated from seed, dormant root, leaf and flowering root of Kobresia capillifolia C.B.Clarke, Kobresia humilis Sergiev, Stipa purpurea Griseb and Ahnatherum inebrians Keng. Determination of IAA secretion of these endophytic bacteria was done by using Salkowski colorimetry. The results showed that 101 among 104 isolates had ability of secreting IAA. IAA secretion was between 1.52 mg·L^-1 and 327.81 mg·L^-1. 73.3% isolates increased IAA secreation with the addition of tryptophan. Endophytic bacteria with strongest ability of secreting IAA were 263XY3(327.82 mg·L^-1),265XY6(146.93 mg·L^-1),266XY1(126.26 mg·L^-1). IAA secretion of 57 isolates were more than 10 mg·L^-1 which was mainly distributed in leaf (30.4%) and flowering root(17.9%) of Kobresia capillifolia C.B.Clarke, and in leaf (10.7%) and flowering root (8.9%) of Stipa purpurea Griseb and Ahnatherum inebrians. The results provided resources and direction for the development and utilization of endophytic bacteria from forage on alpine grassland.

Key words: Endophytic bacteria, IAA, Ecological distribution, Alpine grassland

摘要：

为明确高寒草地优势牧草内生细菌在特殊生存环境下分泌吲哚乙酸（IAA）的能力及其在宿主体内的分布情况，本试验采用Salkowski比色法对线叶嵩草（Kobresia capillifolia C.B.Clarke）、矮生嵩草（Kobresia humilis Sergiev）、紫花针茅（Stipa purpurea Griseb）和醉马草（Ahnatherum inebrians Keng）的种子、休眠期根部、叶部和花期根部内生细菌分泌IAA能力进行了测定。结果表明：在104株供试内生细菌中有101株具有分泌IAA的能力，分泌IAA量在1.52~327.81 mg·L^-1之间，外源色氨酸对73.3%的菌株分泌IAA的能力有促进作用。其中76（75.2%）株的分泌量在0~20 mg·L^-1之间，分泌IAA能力最强的菌株为263XY3（327.82 mg·L^-1），265XY6（146.93 mg·L^-1）和266XY1（126.26 mg·L^-1）。分泌量达到10 mg·L^-1以上的有57株，主要分布于线叶嵩草叶部（30.4%）和花期的根部（17.9%）以及紫花针茅花期的根部（10.7%）和叶部（8.9%）。该结果为高寒草地牧草产IAA内生细菌的开发利用提供了菌种资源和筛选方向。

关键词: 内生细菌, IAA, 生态分布, 高寒草地