Stomatal density of grapevine leaves (Vitis vinifera L.) responds to soil temperature and atmospheric carbon dioxide

Background and Aims: Leaf stomatal density i.e. number of stomates per unit area of leaf, is a primary determinant of the carbon and water relations of plants. However little is known about the plasticity of grapevine stomatal density during leaf formation in response to environmental factors. In this study we determined responses in stomatal density to soil temperature and atmospheric carbon dioxide during leaf development following dormancy to gain further understanding of grapevine carbon and water relations and adaptation to climate change. Methods and Results: Using potted plants of V. vinifera (L.) cv. Chardonnay we found that a period of soil warming from budbreak reduced stomatal density of concurrently-formed leaves whereas CO2 depletion increased it. Furthermore, stomatal density of concurrently-formed leaves was closely and inversely correlated with starch concentration in roots and trunks. Conclusion: We conclude that the stomatal density of grapevine leaves varies greatly in response to soil temperature and atmospheric CO2 concentration. Significance of Study: This is the first study to show that soil temperature influences stomatal density of plants. It also confirms that stomatal density of grapevines, like many other plants, responds inversely to atmospheric CO2 concentration. Our findings demonstrate that stomatal density must be accounted for in any attempt to predict grapevine adaptation to climate change and attendant impacts on CO2 assimilation and water use efficiency in viticulture. More fundamentally, they indicate that the carbohydrate reserve status of perennial, deciduous, plant species may be an important endogenous determinant of stomatal density.