Comparative analysis of seed germination and early growth in Amaranthus thunbergii and Cleome gynandra as affected by pre-treatment methods

Abstract

Background: African Indigenous Leafy Vegetables (AILVs), including Amaranthus thunbergii and Cleome gynandra, contribute significantly to food and nutrition security in rural African communities. However, their utilisation, conservation and domestication are constrained by poor and inconsistent germination associated with seed dormancy, increasing the risk of genetic erosion and limiting their integration into formal food systems. Aim: This study evaluated the effects of seed pre-treatment methods and durations on germination and early seedling development of A. thunbergii and C. gynandra. Setting: Experiments were conducted under controlled laboratory conditions at the Botswana National Seed Laboratory. Methods: Factorial experiments arranged in a Completely Randomised Design (CRD) with three replications were conducted in 2022. Seed pre-treatment methods included control, pre-heating and pre-chilling, while durations comprised pre-heating at 0 s, 30 s, 60 s and 90 s and pre-chilling for 24 h, 84 h and 168 h. Results: Seed pre-treatment methods and durations significantly influenced germination parameters. Amaranthus thunbergii responded more positively to pre-treatments than C. gynandra. Pre-heating for 90 s increased germination of A. thunbergii to 90%, representing a 28% improvement compared with C. gynandra. Pre-heated A. thunbergii seeds reached full imbibition within 3 days, showing a 40% improvement over C. gynandra across all durations. Conclusion: Extended pre-heating enhanced water uptake, accelerated germination and improved early seedling growth in both species by softening the seed coat. Pre-heating is therefore recommended as a practical, low-cost approach to improve germination of AILVs. Contribution: This study contributes empirical evidence to support conservation, domestication and sustainable utilisation of AILVs in Botswana and across Africa.