COMPARATIVE EFFECTS OF VESICULAR-ARBUSCULAR MYCORRHIZAL INOCULATION AND PHOSPHORUS FERTILIZATION ON GROWTH AND PHOSPHORUS UPTAKE OF MAIZE (ZEA-MAYS L) AND SORGHUM (SORGHUM-BICOLOR L) PLANTS UNDER DROUGHT-STRESSED CONDITIONS
O. Osonubi, COMPARATIVE EFFECTS OF VESICULAR-ARBUSCULAR MYCORRHIZAL INOCULATION AND PHOSPHORUS FERTILIZATION ON GROWTH AND PHOSPHORUS UPTAKE OF MAIZE (ZEA-MAYS L) AND SORGHUM (SORGHUM-BICOLOR L) PLANTS UNDER DROUGHT-STRESSED CONDITIONS, Biology and fertility of soils, 18(1), 1994, pp. 55-59
Maize (Zea mays L.) and sorghum (Sorghum bicolor L.) Moench (local var
iety called ''Masakwat'') plants were grown in a sterilized low-P soil
in the greenhouse for 12 weeks. Each plant species was either mycorrh
izal with vesicular-arbuscular mycorrhizal (VAM) fungi, non-mycorrhiza
l but minimally fertilized with soluble P, or non-mycorrhizal but high
ly fertilized with soluble P. Drought stress was imposed after 4 weeks
at weekly intervals. Under unstressed conditions, leaf area, shoot dr
y weights, xylem pressure, and soil water potentials were similar for
VAM and the two non-mycorrhizal P-fertilized treatments but each of th
e VAM-infected species had a greater total root length. Total P uptake
was similar for the maize treatments but higher for VAM than non-myco
rrhizal P-fertilized sorghum treatments. Under drought-stressed condit
ions, the growth parameters and soil water potential were similar for
all maize treatments but they were reduced by mycorrhizal inoculation
in sorghum. Greater water extraction occurred in drought-stressed myco
rrhizal sorghum. In both plant species, total P uptake and P uptake pe
r unit root length (including unstressed species) were significantly e
nhanced in non-mycorrhizal P-fertilized treatments compared with the m
ycorrhizal treatment. Except for the root dry weight of sorghum plants
, there were no differences in the growth parameters and P uptake betw
een minimally and highly P-fertilized non-mycorrhizal treatments for e
ither maize or sorghum. The increased total root length in drought-str
essed mycorrhizal sorghum plants and the similar infected root lengths
in unstressed and drought-stressed sorghum plants may have caused hig
h C partitioning to drought-stressed mycorrhizal roots and therefore c
aused the reduced growth parameters in mycorrhizal plants compared to
the non-mycorrhizal P-fertilized counterparts. The results indicate th
at P fertilization in addition to mycorrhizal inoculation may improve
the drought tolerance of maize and sorghum plants.