Pak. J. Bot., 45(S1): 13-20, January 2013. EFFECT OF AZOSPIRILLUM INOCULATION ON MAIZE (ZEA MAYS L.) UNDER DROUGHT STRESS QUDSIA BANO 1 , NOSHIN ILYAS 1* , ASGHARI BANO 2 , NADIA ZAFAR 1 , ABIDA AKRAM 1 AND FAYAZ UL HASSAN 3 1 Department of Botany, PMAS-Arid Agriculture University Rawalpindi, Pakistan 2 Department of Plant Sciences, Quaid-i-Azam University, Islamabad, Pakistan 3 Department of Agronomy, PMAS-Arid Agriculture University Rawalpindi, Pakistan * Corresponding author: noshinilyas@yahoo.com Abstract Azospirillum strains isolated from water stressed conditions can mitigate drought effects when used as inoculants. In this context, the research was designed to study the effects of Azospirillum lipoferum strain (Accession no. GQ255950) inoculation on biochemical attributes and growth of maize plant under drought stress. Effect of seed inoculation and rhizosphere inoculation were studied in two varieties of maize, which were subjected to drought stress at vegetative stage. Water deficiency affected accumulation of free amino acids, soluble sugars, proline and soluble protein contents. However, seed inoculated plants had an increased accumulation of 54.54 percent and 63.15 percent free amino acids and soluble sugars respectively, while rhizosphere inoculated plants showed 45.45 percent increase in free amino acids and 31.57 percent increase in soluble sugars as compared to control. The concentrations of soluble proteins on the contrary decreased in the similar order. The plants growth aspect i.e. shoot and root fresh weight, shoot and root dry weight, shoot length and root length, also showed results in consistence with the biochemical attributes. Thus Azospirillum strain showed promising effects and can be a potent inoculant for maize that can help the crop to endure limited water availability. Introduction Beneficial rhizobacteria have tremendous potential to facilitate plant growth and productivity, in a number of ways. Another remarkable eminence on the credit of these marvelous creatures is their capability to support plants under stressed environments. When established in soils exposed to abiotic stresses, the populations of rhizobacteria become adapted to such stressed conditions thereby developing tolerance and further they can be isolated to be used as inoculum to support crops grown in correspondingly stressed environments (Sandhya et al., 2010, Khan et al., 2012). They can protect plants against deleterious effects of different environmental stresses to which crop plants are intermittently exposed, like heavy metals, flooding, salt and drought (Mayak et al., 2004). Among such abiotic stresses, drought is becoming more prevalent especially in arid and semi-arid regions of the world, where it sternly influences the crop yields (Sandhya et al., 2010, Hamayun et al., 2010). Soil water deficit is normally the environmental factor in lots of natural settings that compels the furthermost hold back on plant growth (Wahbi & Sinclair, 2007), one of the key environmental features restricting crop yields. It sways more or less all aspects of plant physiology, biochemistry and growth metabolism (Turner & Kramer, 1983), thereby reducing yield (Li, 2007) most decisively, as sufficient availability of water is very critical to growth and development of plants (Shao et al., 2008). Crucial changes in water homeostasis escort to osmotic stress, and are amid primary effects of drought stress. Osmotic adjustment is one among the most frequent acclimatization responses to water deficit that refers to the decreased osmotic potential of the plants by active accumulation of various compatible solutes (Yordanov et al., 2000), like amino acids such as proline, betains and sugars (Mohammadkhani & Heidari, 2008) within the cells in higher concentrations without smashing up the normal metabolism (Choluj et al., 2008). Production of such osmolytes in surplus quantities helps plants to cope up with drought by maintaining osmotic balance of the cell, thereby protecting them against dehydration by stabilization of membrane and protein structures (Hoekstra et al., 2001). Plant microbe interactions intercede to the plant fitness in a variety of ways (Mascher, 2007). Beneficial, symbiotic interactions of plants with microbes can shield plants from biotic and abiotic stresses (Mascher, 2007). Microorganisms have the potential to alter the plant health status and productivity and can elevate crop yield to a remarkable level. The soil microbial communities have definite interactions with plants and can play remarkably important roles in plant growth and development. Microbial strains, isolated from arid or semi arid soils have not been only well adapted to such environments, but also can abet plant mitigate the effects of restricted water availability by improving the plant water status through amplified osmolytes production, when used as inoculants. Azospirillum is one such competent genus of rhizobacteria that can bring about incredible outcomes in context of plant growth promotion and augmenting the drought stress tolerance, when segregated from soils with low water content. The genus consists of free-living plant growth- promoting bacteria (PGPR), capable of affecting growth and yield of copious plant species, many of agronomic and ecological significance (Bashan, et al., 2004). Various studies have accounted that maize is able to hold up free living N 2 fixers in its rhizosphere (Estrada de Los Santos et al., 2001; Ding et al., 2005; Naureen et al., 2005; Perin et al., 2006; Mehnaz et al., 2007). Maize being an important cereal crop, ranked third after wheat and rice globally is also facing water scarcity. Syndhya et al., (2010) wrap up their study by the maxim that improved biomass and average weight; better water relations and reduced water loss are scrutinized due to seeds being inoculated with PGPR, in contrast to the un-inoculated ones under withheld irrigation. Nitrogen fixed by PGPR in rhizosphere, either symbiotically or asymbiotically (Kang et al., 2012), picks