Abstract
Heat stress is an important abiotic constraint limiting crop productivity. An experiment was conducted to elucidate the impacts
of heat induced biochemical transformations on morphological attributes of Pakistani wheat genotypes. Experiment was laid
out in randomized complete block design (RCBD) with the split plot arrangement during the winter season 2014-15. Main plot
treatments were comprised of H0 (No heat imposition) and H1 [(Heat imposition from spike emergence to grain filling initiation
(Feekes Scale = 10.50 to 11.00)]. Subplots treatments were comprised of eleven wheat genotypes (Punjab-2011, AARI-2011,
Galaxy-2013, Millat-2011, Aas-2011, Fareed-2006, Chakwal-50, Mairaj-2008, Pakistan-2013, NIBGE-NIAB-1 and Kohistan97). Under heat over control, lesser decrease in chlorophyll contents and enhancement in antioxidant activities were depicted
by Aas-2011, Chakwal-50, and Mairaj-2008. Higher chlorophyll degradation and diminishment in antioxidant activities under
heat stress over control was observed for all other cultivars. Comparatively lower grain filling rate, higher duration, number of
grains per spike and grain yield was observed for cultivars Aas-2011, Chakwal-50, Mairaj-2008 and Punjab-2011 under heat
stress over control. Conclusively, based on biochemical response and morphological markers genotypes Aas-2011, Chakwal50, and Mairaj-2008 manifested heat tolerance. Genotypes Fareed-2006 and Punjab-2011 manifested medium heat tolerance.
Whereas, genotypes AARI-2011, Galaxy-2013, Millat-2011, Pakistan-2013, NIBGE-NIAB-1 and Kohistan-97 depicted
susceptibility to terminal heat stress
