The physiological response of mungbean (Vigna radiata (L.) R. Wilczek) to drought stress and root-knot nematode infection was studied under greenhouse conditions at King Saud University, Saudi Arabia. A randomized complete block Design (RCBD) with factorial arrangement having three replications was used. Treatments included three water deficit (80%, 40% and 20% of field capacity), two mungbean genotypes (Kawmay-1 and VC2010) and two root-knot nematodem, Meloidogyne javanica (Treub) Chitwood, infection levels (noninfected and infected @ 15000 egg/pot). Results showed that water deficit stress and M. javanica infection significantly hampered most of the studied parameters, except shoot water content (SWC). There were highly significant differences in stomatal conductance, shoot dry weight and leaf area among the tested mungbean genotypes. A significant positive correlation among chlorophyll (a and b) contents, stomatal conductance (SC), leaf area (LA) and shoot dry weight (SDW) was recorded. The outcome of the study also revealed that maximum water deficit stress has adversely affected all parameters except SWC, regardless of the genotype or nematode infection status. Similarly M. javanica infection adversely affected the growth and physiological processes of mungbean plants. Moreover, drought and M. javanica infection had synergistic adverse effects on the growth and physiology of mungbean plants. Results also showed that VC 2010 genotype surpassed kawmay-1 in most of the studied characteristics which

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Stomata conductance (g s ), Shoot water content (SWC), chlorophyll pigments (chl a,b) and enzymes involved in anti-oxidant photo-protection were determined in two mungbean genotypes (Kawmay-1 and VC2010) under greenhouse conditions. The two genotypes were subjected to water deficit stress (20, 40 and 80% of field capacity) and two root-knot nematode (Meloidogyne javanica) infection levels (noninfected and infected at 15000 juveniles per pot). Both water deficit and nematode infection resulted to a fast decline in the chlorophyll pigments, g s and SWC in both genotypes; however, VC2010 was recorded as being comparatively resistant. Increase in antioxidant enzymes activity was detected for superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and polyphenol oxidase (PPO) in both stresses, but this activity was more pronounced in water deficit stress than nematode infection, especially at 40% field capacity. APX and PPO production peaks recorded at 20% of irrigation in VC2010 were highest. This revealed that VC2010 genotype was tolerant to environmental stresses compared to Kawmay-1. It was conceived from the present study that water deficit stress significantly hampered the physiological representatives of plant health, while on the other hand enzymatic alterations to cope with the biotic and abiotic stresses in plants could be used for better tolerability and plant health. The results indicated that oxidative damage (ROS) produced under environmental stress can be minimized by increasing the antioxidant enzymatic activities in mungbean.