BIOLOGIA (PAKISTAN) PKISSN 0006 – 3096 (Print) June, 2016, 62 (1), 95-102 ISSN 2313 – 206X (On-Line) Author’s Contribution: I.A., & M.H., Designed and planned research work; T.H., & M.I., Collected and identified plants; A.G., & S.H.G., Analyzed data statistically: M.H., M.I. & I.A., Wrote and edited manuscript. *Correspondence author: Mishaliftikhar19@gmail.com Establishment of Relationships among changes in Fluorescence, Gaseous Exchange and Growth Attributes under Drought Stress in Maize Cultivars (Zea mays L.) IJAZ AHMAD 1 , MUMTAZ HUSSAIN 1 , TANVEER HUSSAIN 2 , MISHAL IFTIKHAR 3 , ABDUL GHANI 3 , SADAF HONEY GHOURI 3 , MUJAHID HUSSAIN 3 , MUHAMMAD IKRAM 3 & IFTIKHAR AHMAD 3 . 1 Department of Botany, University of Agriculture, Faisalabad, Pakistan 2 Institute of Horticultural Sciences, University of Agriculture, Faisalabad, Pakistan 3 Department of Botany, University of Sargodha, Sargodha, Pakistan ABSTRACT To study physio-biochemical responses of maize cultivars (Zea mays L.) during drought stress conditions, a pot experiment was performed at Botanical Garden, Department of Botany, Agriculture University Faisalabad. Experiment was conducted with 7 maize cultivars i.e., Sadaf, Pak Afgoi, EV-1098, EV-5098, sahiwal- 2002, Agaiti-85, Agaiti-2002, and two drought stress (60% field capacity and control) treatments with 4 replications. The results showed that water stress significantly affected the photosynthetic rate (A) of all maize cultivars. Different maize cultivars showed differential response to water stress. In cvs. Sahiwal-2002, EV-5098 and Agaiti-2002 photosynthetic rate increased while in all other cultivars it decreased significantly. Drought stress also reduced Transpiration Rate (E), Sub – stomatal carbon dioxide (CO2) concentration (Ci), Ci/Ca ratio, Fm (maximal chlorophyll fluorescence), (fluorescence) Fv, Fv/Fo ratio and Fv/Fm ratio of all maize cultivars. However, A/E (water use efficiency) and Fo (chlorophyll fluorescence) values and Fo/Fm ratio were significantly increased with the imposition of water stress. Key Words: Drought resistance, Zea mays, biochemical responses, photosynthetic rate, transpiration rate, chlorophyll fluorescence INTRODUCTION The main abiotic factor is water, which acts as a limiting factor in different crop production regions of the World (Araus et al., 1998). Shortage of water due to irregular and low rainfall in different regions (less than 100 mm) cause heavy crop losses in Pakistan. Any change in low availability of fresh water or rainfall causes increase in aridity and causes the greater crop loss (Athar & Ashraf, 2005; Parry et al., 2006; Tambussi et al., 2007). Drought is the major abiotic factor that has adverse affect on the production of agricultural crops (Lea et al., 2004; Ramachandra et al., 2004). Drought stress has two main types i.e., physiological and physical. Few plats use escaping mechanism in which plants complete their life cycle before physiological water deficiency occurs. Some plants show avoidance mechanism in which plants avoiding dehydration of plant tissues by maximizing water uptake or minimizing water loss, while the others have tolerance mechanism which involves osmotic balance by maintaining high concentrations of solutes or osmo-protectants in living cells (Chaves et al., 2003). At cellular levels and for the whole plants tolerance to abiotic factor is very difficult (Ashraf & Harris, 2004). This is because the interactions between drought stresses, various molecular, physiological and biochemical processes are affecting growth and plant development which ultimately reduce the crop production (Zhu, 2002). The production of stress tolerant crop plants is considered as a best tool to fulfill the demands of food in many parts of the world. However, for the production of these plants requires the knowledge about the genetic traits and physiological mechanisms at different developmental stages of plants. The abiotic stress tolerance mechanism in biotechnology field has provided much information in plants at molecular level in past two decades, (Zhu, 2001). The stress tolerance mechanisms during different stages of plants vary in plant species (Foolad, 1999b; Ashraf, 1994). Most of cereal plants have a range of morpho-physiological adaptations, or processes in order to respond to water stress. However, the physiological attributes are useful and are reliable sources during drought tolerance cultivars/genotypes selection (Tambussi et al., 2007). On the basis of physiological,