Comparative analysis of photoprotection mediated by photosynthetic pigments during summer midday heat stress in rice and wheat

摘要

© 2022, The Author(s) under exclusive licence to Society for Plant Research.An experiment was conducted to assess the comparative diurnal changes in photosynthetic pigments and chlorophyll fluorescence parameters in rice and wheat with an aim to gain insight into the photosynthetic pigments mediated photoprotection during midday heat stress in summer. Rice variety PB 1509 and wheat variety PBW 343 were grown in summer season for exposing them to high temperature condition and observations on photosynthetic pigments, carotenoids composition, pigments profile and chlorophyll fluorescence recorded diurnally in flag leaf on sunny day. In both rice and wheat, values of PSII maximum efficiency (Fv/Fm), photochemical quenching (qP) and PSII actual efficiency (Fv′/Fm′) were reduced during midday while utmost in morning and evening fluorescence (Fo) was noted highest during midday. Similarly, Chla, Chlb, carotenoids, Chla: Chlb, total carotenoids: total Chl ratio and non-photochemical quenching (NPQ) were recorded maximum in noon and higher in rice than wheat. In both rice and wheat photosynthetic pigments profile patterns were similar but pigment bands particularly of chla and zeaxanthin were bold, darker and sharper and having their higher contents in rice. Thus, our results pointed out better photoprotective role of Chla: Chlb ratio and zeaxanthin cycle pigments in rice than wheat. During midday heat stress photosynthetic pigments mediates comparatively stronger photoprotection in rice crop than wheat. Stronger photoprotection mediated by photosynthetic pigments in rice is also one of the adaptations for its cultivation under warm tropical conditions.