Genotypic differences in nitrogen uptake, dry matter production, and nitrogen distribution in pumpkins (cucurbita moschatapoir.)

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Abstract
Thirteen inbred and hybrid pumpkin (Cucurbita moschata Poir.) genotypes, differing on the basis of harvest maturity, were evaluated for NO3‐uptake from solution, dry matter production, and distribution of absorbed N in plant parts, over the 8‐day time‐course corresponding to the period of the vine initiation stage. The pattern of NO3‐ removal from solution was linear in the early genotypes and curvilinear in late genotypes. Genotypic differences in NO3 ‐ absorption were found in early genotypes but not in late ones. In early genotypes, NO3 ‐ uptake from solution was greater in the Fl hybrid than in the parents, but no apparent relationship was found between parents and Fl progeny in their ability to absorb NO3 ‐ from solution. Genotypic differences in dry weight and total N accumulation in roots, stems, and leaves were larger in early genotypes than in late genotypes. Differences in total N concentrations in plant parts among early and late genotypes were small, and occurred only in leaves. As a group, late genotypes removed more NO3 ‐ from solution, produced more dry matter, and accumulated more total N than early genotypes, but differences between individual early and late hybrids were small. The results indicated a positive relationship between NO3 ‐ removed from solution and vegetative growth, suggesting that NO3 ‐ uptake may be a demand driven process.