Responses to drought stress in Prunus sargentii and Larix kaempferi seedlings using morphological and physiological parameters

The frequency and severity of drought are expected to increase due to climate change; therefore, drought tolerance of tree species should be considered before planting for maximal survival in the field. In this study, we examined the response of drought stress in two of the most popular plantation species: Sargent cherry (Prunus sargentii) and Japanese larch (Larbc kaempferi) based on the morphological and physiological characteristics. These plantation species are widely planted in central and northern Asia, especially in Japan and Korea, and also widely used for plantation purpose in northern Europe. Three different irrigation regimes of control (CT; 100% precipitation (P)), light drought (LD; 40% reduction of P), and heavy drought (HD; 80% reduction of P) were applied at the experimental site of Mt Jiri, the Republic of Korea. For morphological responses, both species experienced a significant decrease in leaf size in drought conditions; however, Sargent cherry and Japanese larch experienced reduced leaf width and length, respectively. On the other hand, leaf mass area (LMA, g cm(-2)) increased and branch growth decreased in both species under drought conditions. As physiological responses, drought stress significantly decreased maximum photosynthesis rate (A(max)) and electron transfer rate (J(max)) for both species, while stomatal conductance (G(s)) at A(max) significantly decreased only in Sargent cherry. Drought significantly reduced predawn (Psi(PD)), midday leaf water potential (Psi(MD)), and transpiration in Sargent cherry but not in Japanese larch. In mid-summer, carbon isotopic composition (delta C-13) significantly decreased in Sargent cherry but only showed a reduction tendency in Japanese larch. However, the changes of delta C-13 were not significant in early summer or mid-fall. In the present study, both species showed isohydric and anisohydric characteristics, but Sargent cherry showed greater anisohydric behavior with a steeper slope (Y = 2.132X) and Japanese larch showed more isohydric behavior with a shallower slope (Y = 1.722X). Our results highlight that both species altered their morphological and physiological responses under drought stress; however, the Japanese larch showed greater resistance and resilience in morphological and physiological responses, and in plant-water relations. Therefore, Japanese larch would be more beneficial for plantations in water deficit regions than Sargent cherry.