Transpiration efficiency: further insights from species, sink strength, and soil comparisonsVVadezauthorJKholovaauthorSChoudharyauthorMCooperauthorCMessinaauthorAPrandavadaauthorDuring ID-IV we reported that TE was closely related to the capacity to restrict transpiration under high vapor pressure deficit (VPD). Experiments were undertaken to evaluate other possible factors influencing TE. Experiments across seasons varying in VPD conditions and across water regimes showed that maize had a higher TE than sorghum and pearl millet. While C4 cereals should, theoretically, have similar TE, 100 years of breeding in maize could be responsible for these differences, possibly from increased rates of carbon fixation deriving from selective pressure underincreased planting densities. These results then open an opportunity to accelerate breeding in sorghum and pearl millet by specifically targeting the possible reasons for these differences (RUE, density “resistance”). Further experimentation was undertaken in which ears and panicles were severed from the plants and showed that TE was depressed in maize and sorghum, respectively, while it was not in pearl millet, which produced many new tillers and nodal tillers. This work then raised the question of source-sink relationship in setting carbon demand and then photosynthetic activity. Finally, TE assessed in C4 cereals, grown in four different soils and two different VPD seasons, showed large TE differences among soils during the high VPD season, with a degree of species-by-soil interaction. We interpret these differences to be a consequence of different hydraulic soil properties likely affecting the transpiration response under high VPD. Results will be discussed with regard to breeding targets in “less-bred” crops (pearl millet, sorghum) and with regards to better understanding GxExM interactions.Plant BreedingPearl MilletSorghumPlant Physiology2017-02Conference or Workshop Item