We have analysed daily patterns of leaf elongation rate (LER) in large data sets with 318 genotypes placed in naturally fluctuating temperature and evaporative demand, and examined the effect of targeted alleles on these patterns.

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HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Copyright

The slow-wilting soybean [Glycine max (L.) Merr.] genotype, PI 416937, exhibits a limiting leaf hydraulic conductance for transpiration rate (TR) under high vapour pressure deficit (VPD). This genotype has a constant TR at VPD greater than 2 kPa, which may be responsible for its drought tolerance as a result of soil water conservation. However, the exact source of the hydraulic limitation between symplastic and apoplastic water flow in the leaf under high VPD conditions are not known for PI 416937. A comparison was made in the TR response to aquaporin (AQP) inhibitors between PI 416937 and N01-11136, a commercial genotype that has a linear TR response to VPD in the 1–3.5 kPa range. Three AQP inhibitors were tested: cycloheximide (CHX, a de novo synthesis inhibitor), HgCl2, and AgNO3. Dose–response curves for the decrease in TR following exposure to each inhibitor were developed. Decreases in TR of N01-11136 following treatment with inhibitors were up to 60% for CHX, 82% for HgCl2, and 42% for AgNO3. These results indicate that the symplastic pathway terminating in the guard cells of these soybean leaves may be at least as important as the apoplastic pathway for water flow in the leaf under high VPD. While the decrease in TR for PI 416937 was similar to that of N01-11136 following exposure to CHX and HgCl2, TR of PI 416937 was insensitive to AgNO3 exposure. These results indicate the possibility of a lack of a Ag-sensitive leaf AQP population in the slow-wilting line, PI 416937, and the presence of such a population in the commercial line, N01-11136.

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