AZOSPIRILLUM-MAIZE ASSOCIACION: EFFECTS ON DRY MATTER YIELD AND NITRATE REDUCTASE ACTIVITY
C. M. RIBAUDO; A. N. PACCUSSE; D. P. RONDANINI; J. A. CURA AND A. A. FRASCHINA.
Abstract
Many reports have shown positive interactions between
nitrogen—fixing rhizosphere bacteria of the genus Azospirillum and grain
crop roots. The enzyme that catalyzes the reduction from nitrate to nitrite,
nitrate reductase (NR), is located primarily in the cy-tosol of root cells and
shoot mesophyll cells. The purpose of this work was to examine the effect of
Azo spirillum brasilense strain 42 M on NR activity and dry matter content in
the leaves and roots of two maize hybrids. The performance of the inoculated
plant-bacterial systems was also evaluated in terms of plant biomass andNR activity
in leaves and roots. Plants were grown for approximately 120 days under greenhouse
conditions. The number of replications was 25, and experiments were repeated
four times. Inoculation with Azospirillum showed a significant increase in the
mean dry weight of shoots and roots at the milk ripeness stage. In general,
inoculated plants showed high NR activity in both leaves and roots. Our results
confirm the observations reported by other researchers and encourage further
studies on whether the yields of other crops could be increased in nonfertilized
soils by inoculation with Azospirillum.
Key words:
Azospirillum, maize, dry matter yield, nitrate reductase.