<![CDATA[Global warming poses a significant threat to agricultural sustainability, as high temperatures can disrupt plant physiology and reduce productivity in heat-sensitive crops like cayenne pepper (Capsicum frutescens L.). This study aimed to evaluate the morpho-physiological responses of cayenne pepper genotypes to heat stress. The research was conducted in a greenhouse at the University of Riau, Indonesia, from July to November 2023. The experiment employed a split-plot design; the main plots consisted of two temperature regimes (daily ambient temperature vs. heat stress conditions of 4°C–8°C above ambient), while the sub-plots comprised four genotypes: Pelita, Dewata, Bara, and Taruna. Observed parameters included physiological traits (stomatal conductance, transpiration rate) and morphological traits (plant height, stem diameter, leaf characteristics, flowering, harvest age, and fruit weight). Data were analyzed using ANOVA followed by a Tukey’s HSD test at α = 0.05. The results indicated that heat stress significantly affected stomatal conductance, transpiration rates, and vegetative growth, leading to an overall reduction in fruit weight across all genotypes. However, specific adaptive responses varied. The Taruna genotype demonstrated superior physiological adaptation, characterized by stability in stomatal conductance, chlorophyll content, and leaf morphology. Conversely, in terms of yield, the Dewata genotype produced the highest fruit weight per plant under heat stress conditions compared to Pelita, Bara, and Taruna. These findings highlight that while Taruna exhibits robust physiological defense mechanisms, Dewata maintains better production potential under thermal stress, providing critical genetic resources for developing climate-resilient varieties.]]>
