The need to incorporate fast and slow relaxation kinetic parameters into photosynthesis-measuring systems

Increasing global population demands the doubling of crop production by 2050. Advancements in agricultural techniques make it possible to increase the rate of crop improvement, though utilization of molecular tools to identify traits related to yield and stress tolerance is poor. The development of effective physiological selection criteria that are fast and nondestructive, particularly those related to yield and stress tolerance, will help in developing improved crop cultivars. In plant stress physiology, established chlorophyll fluorescence parameters, such as the efficiency of photosystem II (Phi PSII), photosystem I electron transport rate (PSI ETR), and non-photochemical quenching (NPQ), have received attention. The photoprotective processes conferred by NPQ serve fundamental roles in maintaining plant fitness and sustainable yields where their importance in predicting crop performance and yield under normal or stressful environments has been widely recognized. In this review, we focus on two informative parameters, - q(E) and q(I),- which are components of NPQ that have been ignored by most photosynthesis-measuring systems. We argue for adding these parameters to photosynthesis machines as calculating them later can be cumbersome and their inclusion will help plant breeders and non-specialists in phenotyping using chlorophyll fluorescence. (C) 2019TheAuthor(s). Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative.