Cucurbit species have epigeal cotyledons adapted for both storage and photoassimilation functions. Seedling dependence on cotyledonary leaves for initial growth and establishment was quantified for hybrid squash (Cucurbita maxima x C. moschata), watermelon (Citrullus lanatus), cucumber (Cucumis sativus), and bottlegourd (Lagenaria siceraria). One or both cotyledons were excised at 3; 6; 9; and 12 days after emergence (DAE) and initial growth was compared to control seedlings (with intact cotyledons). Initial growth was quantified at 3-day intervals, from emergence until 21 DAE, by assessing expansion rate of cotyledonary leaves, time from emergence to achieve equivalence between leaf and cotyledonary area, and total dry matter production. Squash showed the highest expansion rate of cotyledonary leaves, the shortest time to achieve equivalence between leaf and cotyledonary area, and the highest total dry matter production. Squash and cucumber seedlings showed higher dependence on cotyledonary leaves than watermelon and bottlegourd. Impairment of cotyledonary leaves, depending on species, cotiledon damage level and seedling physiological age, can drastically affect initial growth and establishment of seedlings, therefore leading to yield reductions in cucurbits.
Cucurbita maxima x C. moschata; Citrullus lanatus; Cucumis sativus; Lagenaria siceraria; photoassimilates partitioning
