Variations in seasonal drought tolerance rankings

Drought is one of the most common and significant disorders affecting tree establishment and growth, in the urban environment. Consequently, improving tree selection by the provision of quantifiable tolerance data by which to evaluate genotypes is an important area of scientific research. A number of in vitro studies address drought tolerance in isolation, at a single time point during the growing season. Using an in vitro foliar dehydration method to evaluate closely related genotypes of Acer platanoides, A. pseudoplatanus and A. campestre, drought tolerance rankings were not found to be consistent throughout the growing season (spring, summer and autumn). i.e., A. pseudoplatanus 'Negenia' was found to be comparatively drought tolerant in spring, but displayed moderate to low comparative tolerance in summer and autumn; as measured using in vitro foliar dehydration as a proxy for drought tolerance. Drought conditions are most severe and common in summer; however, this study discusses the need to consider spring tolerance in addition to summer or autumn, particularly when selecting trees for tough urban sites, prone to drought stress across all three seasons.