Effect of Water Stress on Growth and some Biochemical Traits of Three Pear Genotypes from Kurdistan Province

In order to study the effects of different levels of water stress on growth and some biochemical traits of three pear genotypes (Nazkeh, Lasoreah and Kevilah), a pot experiment was established. Three pear genotype seedlings from Kurdistan province were exposed to four water supply regimes. Control seedlings were kept well watered everyday. Water stress treatments were irrigated when soil water potential reached – 0.4, -0.8 and -1.2 MPa. Plant height, stomatal density, leaf chlorophyll content (chlorophyll a, b as well as total) water were assessed following the stress period, but proline and Total Soluble Sugar (TSS) were determined both during water stress and after the plants being rewatered. The results of statistical analysis revealed that stomatal density and leaf chlorophyll contents (a, b and total) were not affected by stress treatments. Water stress exerted significant effects on growth and biochemical characteristics. Plant height decreased during water stress. Plant growth stopped in -0.8 and -1.2 treatments in Nazkeh and Lasoreh but plant height increment was 9.4 % of control in Kevilah in -0.8 MPa treatment. Kevilah had a higher growth rate in -0.4 MPa treatment as compared with the other genotypes. Proline and total soluble sugars increased during water stress period but reache the control levels 2 days past rewatering in all water stress treatments. The free proline and TSS content of leaves in Kevilah genotype increased at a higher rate when in water stress conditions. The highest contents of proline and TSS were observed in Kevilah genotype in -1.2 MPa treatment. The results indicated that Kevileh genotype was more resistant to drought stress.