An automated whole-canopy multi chamber system for live monitoring water use efficiency in sorghum

Plant growth and productivity are strongly affected by limited water availability in drought prone environments. The current climate change scenario, characterized by long periods without precipitations followed by short but intense rainfall, force plants to implement different strategies to cope with drought stress. Understanding how plants use water during these period of limited water availability, and which are the molecular mechanisms at the basis, is of primary importance to identify and select the best adapted genotypes to a certain environment. Two sorghum genotypes, previously characterized as drought tolerant and drought sensitive, were subjected to progressive drought stress through a dry-down experiment protocol. An automated multi-chamber system was used in this experiment to determine in vivo whole-canopy water use efficiency. This system allows to record five measurements per hour of the whole-canopy transpiration and photosynthetic rate and to calculate instantaneous water use efficiency. In this experiment the transpiration and net photosynthetic rate were coupled with gene expression daily dynamics of drought related genes. The drought tolerant genotype showed an increased expression in all the genes tested, whilst the drought sensitive genotype had an opposite trend for some of them. In particular, the daily expression trend of two genes, one coding for a carbonic anhydrase and the other for a mitochondrial K+ channel, was highly correlated with the daily trend of transpiration rate, indicating that these genes are highly involved in the control of stomatal aperture in both genotypes. The daily trend of a putative ERECTA-like gene expression could be overlapped to the daily trend of water use efficiency of the two sorghum genotypes subjected to drought stress, enabling to promote this gene as marker for screening selection for water use efficiency trait in sorghum.