Temperature stress induced anatomical and histological alterations in reproductive organs of Capsicum annuum L.

Capsicum annuum L. comprising hot pepper and sweet pepper, is highly vulnerable to temperature extremes, which adversely impact fruit and seed set in Capsicum species. The present study investigates the anatomical and histological changes in the male and female reproductive organs of Capsicum genotypes under temperature stress. The study includes sweet pepper (Capsicum annuum var. grossum) exposed to low temperature conditions and hot pepper (Capsicum annuum var. annuum) genotypes differing in heat tolerance under high temperature stress. Using Periodic acid–Schiff (PAS) and Haematoxylin–Eosin (H&E) staining techniques, we examined cross-sections of anthers and ovaries to assess tissue integrity, carbohydrate accumulation, pollen development and ovary structure. In sweet pepper, low temperature stress resulted in abnormal ovary enlargement with vascular bundle degeneration, increased giant cell counts and excessive PAS-positive staining in anther tissues, indicating disrupted carbohydrate utilization. Although pollen count remained relatively unaffected, the structural disorganization in ovules and tapetum suggested compromised reproductive function. In hot pepper, the heat-tolerant genotype maintained clear anther architecture, higher pollen viability and intact ovary tissues, whereas the susceptible genotype exhibited significant degeneration of vascular bundles, increased giant cell count, reduced pollen count and low PAS reactivity. The results highlight the sensitivity of reproductive organ development to temperature extremes and reveal histological traits that differentiate tolerant and susceptible genotypes. These findings provide a foundational understanding of the anatomical basis of temperature stress tolerance in Capsicum genera with implications for breeding thermo-tolerant genotypes.