Morphological and physiological responses to drought stress in eleven genotypes of the Juniperus species

Drought is one of the most prevalent and critical environmental stresses affecting a variety of plants, particularly ornamental plants. One of the useful methods to alleviate the effect of drought stress is to screen for and develop drought-tolerant varieties. In this study, a factorial experiment based on the completely randomized design was conducted to investigate the responses of ۱۱ genotypes from different Juniperus species at two irrigation regimes (normal, drought: not irrigated for a four-week period) in terms of growth and biochemical characters.Drought stress had a significant negative impact on the assessed growth characters. The G۳ and G۸ genotypes had the highest root fresh weight and root dry weight at both normal and water-deficit stress conditions. G۳ showed the highest root volume at normal conditions but at the drought stress, the highest root volume belonged to G۱ and G۸. At drought stress conditions, the leaf fresh weight and dry weight of G۹, G۸, G۶, G۴, G۳ and G۱۱ were higher than other genotypes. The stem fresh weight of G۳ and G۱۱ and the stem dry weight of G۱۱ and G۸ manifested higher values than other genotypes when water deficit stress was imposed. Stem diameter decreased in the seedlings at the drought stress, however, G۲, G۳, G۴, G۸, G۹ and G۱۱ had higher values than others at stress conditions. The relative water content decreased in the plants under stress, however, the reduction in G۳, G۵ and G۶ were smaller than the rest of the genotypes. Among the genotypes, G۵ and G۳ showed the highest antioxidant activity under water-deficit stress. The genotypes G۱, G۶, G۷ and G۸ had also a notable increase in the antioxidant activity at drought stress conditions. Under drought stress, the highest increase in the proline content belonged to G۳ followed by G۵, G۶ and G۷ and the G۵, G۶, G۱۰ and G۸ genotypes had the highest amount of soluble sugars. In conclusion, G۳ (Juniperus chinensis var. Sargentii) and G۸ (Juniperus chinensis ‘Kallayʼs Compact’) showed mainly better performance under drought stress, which can be suggested as candidate drought-tolerant genotypes to be used in breeding programs for the sustainable development of urban landscape in arid and semi-arid areas. Although G۵ (Juniperus procumbens ‘Nana’) had low biomass in this experiment, it showed high antioxidant activity, proline and soluble sugars at the drought stress conditions. Therefore, further investigation is needed, especially at more severe drought stress conditions, to elucidate its outstanding response to drought stress in terms of antioxidant activity and proline and soluble sugars content.

Keywords:

Antioxidant Activity , Drought Stress , Juniperus , Morphological and physiological characters