Association of photosynthetic traits with water use efficiency and SPAD chlorophyll meter reading of Jerusalem artichoke under drought conditions

The impact of water stress on plant growth, tuber yield and inulin content has been widely studied but there is limited information on the effect of drought on photosynthetic characteristics. Therefore, this study was to investigate the effect of water stress on photosynthetic characteristics in Jerusalem artichoke genotypes with different levels of drought tolerance. Two experiments were conducted in rhizobox under greenhouse conditions during August to October in 2015 and 2016. A factorial experiment in randomized complete block design with three replications was used. Factor A were two water regimes (irrigated = field capacity; (FC) and water stress) and factor B were three Jerusalem artichoke genotypes. Data were recorded for relative water content, SPAD chlorophyll meter reading (SCMR), photosynthetic characteristics and water use efficiency (WUE) at 7 and 30 days after imposing drought. Leaf area and dry matter was recorded at 30 days after imposing drought. Our results revealed that drought caused a greater reduction in stomatal conductance (gs), net photosynthetic rate (Pn), leaf area and biomass production than in other traits measured. In contrast, WUE and SCMR were increased under drought conditions. However, gs and Pn decreases were less in resistant Jerusalem artichoke genotypes than in susceptible genotypes. Also, resistant genotypes had higher WUE increases than susceptible genotypes. Improved Pn combined with high WUE could contribute to higher biomass production. Interestingly, SCMR was associated with Pn and this trait could be used as surrogate trait for improved Pn under drought conditions.