Giordani T. Buti M. Natali L. Pugliesi C. Cattonaro F. Morgante M. and A. Cavallini. 2011. An analysis of sequence variability in eight genes putatively involved in drought response in sunflower (Helianthus annuus L.). TAG 122:1039-1049. (Article communicated by A. Berville)

From Materials and methods:

“For analyses of drought response, plantlets were grown in a growth chamber at 23C, 0.7 kPa vapour pressure deficit (VPD). A 16-h photoperiod was provided by mer- cury lamps (Osram HQI-TS 250W/NDN, Wembley, UK) with intensity of 200 lmol m-2 s -1 . Plants were watered to pot capacity twice daily. Leaf discs (1.5 diameter) punched from expanded leaves (3rd node) of 4-week-old plants were used for relative water content (RWC) measurements. Leaf discs were placed on a bench at 23C, 0.7 kPa VPD, under light (200 lmol m-2 s -1 ), with the abaxial surfaces uppermost and allowed to dehydrate for 2 h. Measurements were performed every 30 min, using five leaf discs punched from different plants for each genotype. RWC was calculated etc’…”

It has already been well established that unnatural and irrelevant dehydration treatment of plants results in artifacts which are expressed physiologically or genetically. Stress must approach real conditions mainly in terms of a slow rate of development. Dehydration stress should be applied to the whole plant for a number of reasons. For example, root drying is also part of the adaptive response.