Physio-morphic traits as influenced by seasonal variation in sunflower: A review

Owing to its wide adaptability, sunflower can be planted twice a year in spring and autumn. Nonetheless crop performance is strongly influenced by this seasonal variation. In this regard, morphological and physiological performance of spring sown sunflower is slower during early season than that sown in the autumn. Nonetheless progressive increase has been witnessed in physio-morphic functions like allometry and assimilation rate with the progressive rise in temperature during spring, however any increase in temperature, after the critical limit, may result in substantial decline in physio-morphic expressions. Any decrease in temperature later in the season may suppress the performance of autumn sown sunflower. Agronomic and yield traits such as, plant height, achenes number per head and achenes weight are also influenced by temperature and growth duration and finally affect the crop yield. Decrease in ambient temperature markedly influences the physio-morphic expressions of sunflower during both vegetative and reproductive growth phases. Seasonal variability in sunflower performance regarding physio-morphic traits indicated better capture and utilization of environment-driven resource (temperature, light, photoperiod & soil water) during spring compared to autumn sowing in the sub humid conditions of Pothwar. Usually there is a linear relationship amongst growing degree days, yield and yield related traits during both spring and autumn seasons. Here we discuss the influence of environmental variation on morphological and physiological characteristics in sunflower.