Effect of Plant Growth Regulators on Sweetpotato Stem Tissue Development and Structure

Sweetpotato (Ipomoea batatas) is an important global food crop, yet propagation through greenhouse-produced slips is limited by low transplant establishment rates. Previous studies have focused on external morphological traits to improve transplant quality, but the internal anatomical structure of sweetpotato slips remains largely unexplored. This study examined the effects of four plant growth regulators (PGRs)—flurprimidol, paclobutrazol, uniconazole, and indole-3-butyric acid (IBA)—applied foliarly at varying rates to sweetpotato slips grown in a greenhouse. Cross-sections of the stem were stained with toluidine blue O and analyzed microscopically to assess epidermal, collenchyma, parenchyma, and xylem tissue thickness. Flurprimidol at 120 mg·L−1 significantly increased epidermal thickness by 31.8% compared to the control. Paclobutrazol at 30 and 60 mg·L−1 significantly reduced collenchyma thickness by 37.8% and 39.7%, respectively. Other treatments showed no statistically significant differences across measured tissues, although some trends were observed. These findings suggest that certain PGRs may influence internal slip anatomy, particularly the epidermis, which could improve transplant resilience and field performance. Further research is needed to optimize application rates and evaluate long-term agronomic outcomes of anatomical modifications in sweetpotato slips.