Growth, nodulation and N 2 fixation in Dalbergia sissoo inoculated by Azospirillum brasilense and Acaulospora laevis under different moisture levels
Ethiopian International Journal of Multidisciplinary Research
Under the pot culture, using sterilized soil, different regimes of moisture influences the growth nodulation and N 2 fixation of single (Azospirillum brasilense+ AM, alone) and dual inoculation (Azospirillum brasilense+AM) Dalbergia sissoo.In dual inoculation with Azospirillum brasilense and Acaulospora laevis found to be raised maximum as in growth nodulation, nitrogen fixation and percentage of AM colonization of roots were considerably influenced with the increase in moisture stress
... ure stress from-0.3MPa to-1.5MPa. At-0.3MPa level, the growth of plants and total N content. In other water regimes, the values of all the above parameters shows decrement with the increase in moisture stress and also shows that,that plants with dual inoculation performed better than single inoculated plants. Above observation counted a protective role played by AM in providing resistance to Dalbergia sissoo against injurious effects of moisture stress. INTRODUTION Like most root-inhibiting and soil born fungi, Mycorrhizal fungi exist as spores in soil or as vegetative propagate, throughout the world and sform symbiotic relationship with the most terrestrial plant's roots.Habitants of arid deserts and aquatic environment ,Arbuscular mycorrizal fungi are wide range of soil water regimes tolerant.Negative impact on nodule function , photosynthesis inhibition and disturbance of delicate mechanism of oxygen control in nodules is a constant agricultural constraint in the semi-arid tropics due to drought stress.AMF symbiosis can protect host plants against detrimental effects caused by drought stress [3,4] and can also reduce the impact of environmental stresses such as salinity . Metabolic influence due to moisture stress can show extreme result not only in impaired gas exchange but also in considerable alteration of physiological process [6, 7]. Available reports indicate that plants infected with mycorrhizal fungi grow better even under stress condition  and AM association in plants plays vital role towards the development of resistance to water stress [9, 10].Leguminous plants respond more to mycorrhizal infection due to requirement of P than cereals, and indirectly enhances the biological nitrogen fixation, especially in soil with low P content by increased P availability. This study discusses the effects of inoculation of Azospirillum brasilense alone and in combination with Acaulospora laevis on growth and nitrogen fixation in Dalbergia sissoo a tree legume, under different moisture stress. MATERIAL AND METHODS The role of the most preferred AM Acaulospora laevis on resistance recovery from moisture stress of test plants inoculated with most efficient Azospirillum brasilense was studied by conducting a pot culture experiment using sterilized soil for six months. The surface sterilized seeds pelleted with Azospirillum brasilense isolates, were sown in pots on AM inoculum pad containing 250 spores/50 g soils. Four seedlings were maintained in each of the five replicates for their individual treatment. Each of these treatments consists of uninoculated control, Azospirillum brasilense alone, AM alone and Azospirillum brasilense+ AM inoculated sets. These were separately maintained at five different soil moisture levels. Soil moisture content was determined in terms of MPa (matric potential) level (1MPa=10bars) by using thermocouple psychometer. The five water regimes were (i) water once to the field capacity in 24h (-0.3MPa), 36h (-0.6MPa), 48h (-0.9MPa), 72h (-1.2MPa) and 96h (-1.5MPa). The plants were subjected to above moisture regimes after two months of their establishment. The above maintained matric potential were approximately equal to soil moisture levels. Following parameters were selected for the study of shoot-root length, shoot and root dry weight, total plant protein , total chlorophyll , total nitrogen and phosphorus content , nodule number, nodule dry weight and maximum nodule size , nitrogenous activity  of root nodules and percentage of AM colonization by roots.