Improve crop water-use efficiency through enhancing harvest index in cereals

摘要

Water-use efficiency (WUE), defined as biomass accumulation over water consumed, may be a highly inheritable characteristics. In practice, WUE can also be enhanced by less irrigation, particularly via stomatal control. However, such enhancement is largely a trade-off between lower biomass production and higher WUE. We have presented a case here that WUE may be enhanced through an improved harvest index. Harvest index has been shown as a variable factor in field crop production, especially in cases where whole plant senescence of rice and wheat is unfavourably delayed. Such delayed senescence can delay the remobilisation of pre-stored carbon reserves in the straw, and result in lower harvest index. A controlled soil drying, i.e. moderate drying such that overnight rehydration of plants is still possible, should enhance whole plant senescence, and therefore improve the remobilisation of pre-stored carbon reserves. The gains from the improved harvest index may outweigh a possible biomass loss due to a shortened photosynthetic period in grain filling, such as at high N supply, or in lodging-resistant cultivars that stay green for too long, and hybrid cultivars with excessive heterosis. The harvest index and WUE can be substantially improved in these cases.