Evapotranspiration partitioning and variation of sap flow in female and male parents of maize for hybrid seed production in arid region

Understanding the variation of sap flow in female and male parents of maize for hybrid seed production and evapotranspiration (ET) partitioning is useful in accurately determining water use of the female and male parents and improving irrigation management of maize for hybrid seed production. Sap flow rate, ET, soil evaporation (E), meteorological variable, soil water content (SWC) and morphological parameters in female and male parents were measured during April to September in both 2013 and 2014 in the arid region of northwest China. Sap flow rates in female and male parents and E were respectively monitored using heat-balance technique and micro-lysimeter. We found that the variations of sap flow rates in female and male parents were similar during the vegetative growth stage, but the female parents had higher sap flow rate per plant than the male parents after the detasseling, with the maximum difference of daily sap flow rate per plant of 0.28-0.33L d⁻¹. Hourly sap flow rates in female and male parents were highly correlated with net radiation, while daily sap flow rates in female and male parents were highly correlated with net radiation, SWC, leaf area index, but not correlated with crop height. Daily E increased exponentially with SWC. Moreover, daily sap flow rates in the male parents were positively correlated with stem diameter. The total ET was 363.31-384.15mm over the whole growth stage of maize, and the transpiration (T) of female parents per ground area accounted for 63–80% of the total ET, while the T of male parents per ground area accounted for 4–14% of the total ET, primarily due to different planting quantities between the female and male parents. And the soil evaporation was 47.77-62.21mm over the whole growth stage, accounting for 13–16% of the total ET. Our results can provide scientific basis for accurate determination of water use of female and male plants and developing precise irrigation scheduling of maize for hybrid seed production in the arid region.