Abstract
Response of a wheat variety, Pato as,entina, to salinity and hypoxia was studied under green-house conditions using hydroponic technique. Wheat seedlings were exposed to stepwise NaCl salinity while hypoxia conditions were created by stopping aeration and surface seedling of the 15 strength Hoagland nutrient solution. Shoot and root growth was negatively affected by salinity and hypoxia when applied sepa-rately, the combined effect being more injurious. Effect of salinity and hypoxia on ionic concentrations (K+, Na+, Cl") and chlorophyll a and h contents in wheat leaf has been discussed.
INTRODUCTION
in rice growing areas of Pakistan, soil permeability and infiltration are generally negligible due to deteriorated structure, higher clay as well as silt contents and domi-nance of Na in some cases, Therefore, ap-plication of irrigation or rains during the 'kharir season create waterlogged condi-tions, particularly for wheat which is com-mon crop following rice in these fields. Since wheat, unlike rice, is sensitive to hypoxia (low oxygen) conditions, its production is se-riously decreased. The typical responses of wheat to wa-terlogging include early leaf senescence, slow shoot growth, cessation of seminal root elongation and/or decreased nutrient up-take (Trought and Drew, 1980). Such changes could he due to limited generation of metabolic energy during the exposure of roots to hypoxia (Luttge and Higinbotham, 1979) and perhaps due to increased mem-brane permeability (Jackson and Drew, 1984). Previously differences in varietal re-sponse of wheat to hypoxia conditions have been reported (Buwalda et al., 1988 a), We have studied the response of an exotic wheat
variety, Pao argerztino, to salinity waterlog-ging and their interaction with respect to its growth and ionic relations.
MATERIALS AND METHODS
Ten-day old seedlings were transferred to 11 strength Hoagland nutrient solution in plastic containers. Salt stress was developed stepwise by adjusting an increase in EC of the nutrient solution by 3 dS m-1 with NaCI after every 24 hours. Hypoxia conditions were created by with-holding the aeration of the solutions and scaling the top of the con-tainers with plastic sheet to eliminate gas ex-change. Plants were harvested after 20 days growth period. Data on various growth pa-rameters were recorded and statistically analysed following completely randomized design. Duncan's Multiple Range test was used to determine the significance of results (Steel and Torrie, 1980). Composite leaf samples were kept in the eppendorf tubes which were stored in the deep freezer, Cell sap was expressed by pressing leaf material with a pointed glass rod
