چكيده لاتين :
Introduction: Iran is located in arid and semi-arid regions, so limitation of precipitation and poor distribution of rainfall with prolonged periods of heat and drought have caused harsh conditions for establishing plants. In general, previous researches have shown that water deficit or drought stress had destructive effects on morphological, physiological and biochemical parameters of plants. So that, researchers stated that the first reaction of plants to water stress was decline in growth. Growth parameters such as height, fresh and dry weight of root and stem and leaf area could decrease with increasing water stress. Therefore, use of methods for reducing water evaporation from soil, decreasing run-off and improving transport nutrients were considered in recent years. Superabsorbant polymers are one of the most important compounds in reducing negative effects of drought on plants.
Materials and Methods: This study was conducted to investigate the effect of five different levels of super AB A200 polymer (0, 1, 2, 3, 4 g/Kg of soil) and three levels of irrigation [100 as control, 65 and 30 percentage of plant evapotranspiration potential (ETcrop)] on morphological characteristics of two olive cultivars ‘Baghmaleki’ and ‘Dezphol’ as a factorial experiment based on randomized complete block design with three replications. In this experiment, ninety 18-month-old olive trees of ‘Baghmaleki’ and ‘Dezphol’ were kept for adaptation in greenhouse for one month.The plants were planted in ninety pots including 1/3 sand, 1/3 manure and 1/3 soil with superabsorbent polymer. Superabsorbent polymers (super AB A200) were prepared from Company Rahab Resin (Licensed by Iran Polymer and Petrochemical Institute). Then, the plants were irrigated with 100%, 65% and 30% ETcrop, every three days. Finally, morphological parameters such as root fresh weight, root dry weight, shoot fresh weight, shoot dry weight, height, leaf number, leaf Area and leaf area ratio were measured. Data analysis was performed using MSTATC software and mean comparison was done by Duncan ʹs multiple range tests at 5 and 1% probability.
Results and Discussion: The results showed that interaction effect between irrigation and polymer affected shoot fresh weight, leaf fresh weight, shoot dry weight, leaf dry weight, height and leaf area ratio at p <0.01, whiles interaction between irrigation, polymer and cultivars affected height, root dry and fresh weights at p <0.01. Furthermore, all of measured traits were reduced greatly by reducing water from 100% to 30% ETcrop. Fresh weight for root, leaf and shoot, and dry weight for root, leaf and shoot were decreased by 29.23%, 15.76%, 15.77%, 26.25%, 13.5% and 14.73 %, respectively in irrigated plants with 30% ETcrop in comparison with control. Some researchers stated that limitation of photosynthesis could be one of the important factors for reducing growth under drought. Furthermore, drought could affect directly on cell turgor potential and reduced cell division,cell enlargement and plant growth. Also, our findings revealed that shoot fresh weight (19.72 g), shoot dry weight (12.94 g), leaf fresh and dry weights (15.6 and 10.12 g), leaf area (210.55 cm2) and leaf area ratio (6.02) were obtained in irrigated plants with 30% ETcrop and untreated with polymer. The results showed leaf number was highest in ‘Baghmalek’cultivar irrigated with 100% Etcrop (465) and lowest in ‘Dezphol’ cultivar irrigated with 30% Etcrop (328.13). The highest value of leaf area and leaf area ratio was obtained in 3 g polymer per Kg soil in ‘Baghmalek’ cultivar. In addition, root fresh and dry weights and plant height were 36, 49.7 and 27 % greater in ‘Baghmalek’ cultivar treated with 30% ETcrop and 4 g polmer per Kg soil comparison with ‘Baghmalek’ cultivar treated with 30% ETcrop and whiout polymer.
Conclusions: Drought or water deficit could affect directly on cell turgor potential and reduced cell division, cell enlargement, photosynthesis and plant growth. The use of superabsorbent polymer could absorb abundant water and release it easily, so the plant will have a better growth condition in this situation. Our results showed that Baghmalek cultivar had lower sensitive than Dezphol cultivar to water deficit and it suggested that Superabsorbent polymers can be used to discipline drought in some areas that rainfall shortage and water deficit is the most important problems.
