Pengaruh Hormon Asam Indol Asetat yang Dihasilkan Azospirillum sp. terhadap Perkembangan Akar Padi

Puji Lestari, Dwi N. Susilowati, Eny I. Riyanti


Free-living bacteria of the
genus Azospirillum live in close association with rice roots.
This bacteria produced indole acetic acid (IAA), a plant
growth hormon, to the environment. IAA was isolated from
cultures of Azospirillum strains and investigated for its effect
on root development and plant height of rice variety IR64 in
vitro. Rice cultures of variety IR64 were grown in vitro and
inoculated with cultures of Azospirilllum. Production of IAA
by the bacterium during its growth period in rice culture medium
containing different levels of nitrogen was observed.
Results of the experiment showed that strains Azospirillum
Az15 and Az44 had a high ability to produce IAA, i.e., 57.93
μg/ml at 12 days after incubation (DAI) and 40.42 μg/ml at 7
DAI, respectively. The IAA production pattern of Azospirillum
Az15 and Az44 in the liquid medium were fluctuative
until the end of the incubation period, while that of the strain
Az7 was linier. Strain Az7 gave a better effect on the root
development and plant height than strains Az15 and Az44.
Treatment combination of strain Az7 and 100% nitrogen gave
highest root development. High level of nitrogen increased
IAA content in the uninoculated culture, while low IAA
content on the inoculated one. Inoculation the culture with
strain Az7 together with 50% nitrogen application resulted in
the IAA content, root dry weight, root length, fiber root number,
and plant height as high as those on cultures containing
100% nitrogen (1 mM NH4NO3) without inoculation. Inoculation
of rice culture with Azospirillum is expected to reduce
nitrogen application on rice IR64 by the IAA production as
indicated by significant changes in the root growth and
development. A higher concentrations of IAA tend to give
better effects on the root growth and development of rice


Azospirillum; indole acetic acid; nitrogen fertilization; rice plant.

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P-ISSN : 1907-1094
E-ISSN : 2549-1547

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