Physiological responses of rosewoods Dalbergia cochinchinensis and D. oliveri under drought and heat stresses

Dalbergia cochinchinensis and D. oliveri are classified as vulnerable and endangered respectively in the IUCN Red List and under continued threat from deforestation and illegal harvesting for rosewood. Despite emerging efforts to conserve and restore these species, little is known of their responses to drought and heat stress, which are expected to increase in the Greater Mekong Subregion where the species co-occur and are endemic. In this study of isolated and combined drought and heat effects, we found that D. oliveri had an earlier stomatal closure and more constant midday water potential in response to increasing drought level, suggesting that D. oliveri is relatively isohydric while D. cochinchinensis is relatively anisohydric. Heat shock and drought had synergistic effects on stomatal closure. Our results indicate contrasting relationships in water relations, photosynthetic pigment levels and total soluble sugars. An increase in chlorophyll a was observed in D. cochinchinensis dur...