Enhancing Germination Performance in Crescentia cujete L. (Calabash Plant) Using Ascorbic Acid and Thiourea

Crescentia cujete L., the calabash tree, presents a promising, sustainable alternative to plastic. Nevertheless, erratic seed germination impedes its widespread propagation. This study explored the effectiveness of thiourea and ascorbic acid pre-treatments in enhancing C. cujete seed germination. Seeds underwent priming with thiourea and ascorbic acid at concentrations of 100 ppm and 500 ppm, across six different durations: 1, 3, 5, 24, 48, and 72 hours. Subsequent evaluation of germination parameters revealed that both the priming substance and the duration of exposure significantly affected germination. Optimal germination success was achieved with a three-hour priming using 100 ppm thiourea. This treatment resulted in a 45% germination rate by the second week, increasing to 49.5% by the third week, and peaking at 79.6% in the fourth week post-treatment. Conversely, a five-hour exposure to 100 ppm thiourea completely inhibited germination over the six-week observation period. Ascorbic acid also initiated sprouting; however, its final germination rates consistently remained below 50% at the 100 ppm concentration, regardless of exposure duration, falling short of the most effective thiourea applications. Beyond germination, these pre-sowing treatments positively impacted seedling development. For example, plants from seeds treated with 100 ppm thiourea for 5 hours exhibited a leaf area of 0.9 cm, while those exposed for 48 hours reached 1.73 cm. These findings suggest that seed priming, particularly with thiourea, offers significant potential to improve C. cujete propagation and early growth, thereby bolstering its role as a sustainable resource.