Phosphorus Nutrition Influence on Plant Growth and Nonstructural Carbohydrate Accumulation in Tobacco

Abstract

Low phosphorus nutrition generally results in increased leaf starch accumulation. The objective of this study was to determine how P nutrition, ranging from deficient to supra‐optimum, affected plant growth and development and accumulation of nonstructural carbohydrates within the plant canopy. Tobacco (Nicotiana tabacum L. cv. KY 14 and Speight G28 and N. rustica L. cv. Pumila) plants were grown in the greenhouse in pots of soil that contained six (Exp. 1) or seven (Exp. 2) levels of P (P1‐P7, ranging from 0–2150 ha‐1). Plant growth increased with P level up to P4 (269 kg P ha‐1), whereas leaf P levels remained essentially constant up to P3 (134 kg P ha‐1) or P4. Above P4, growth was constant but leaf P levels continued to increase. Increased leaf P at high fertility rates did not influence nonstructural carbohydrate accumulation. Photosynthetic capacity was depressed below P4, but the decrease was not as great as the decrease in growth. Leaf sucrose levels were unaffected by P fertility. Starch levels were differentially affected by P fertility depending on the cultivar. For both G28 and Pumilla, low P fertility led to decreased starch accumulation. For KY 14, low P fertility led to increased starch accumulation. The activity of adenosine diphosphate glucose (ADPG) pyrophosphorylase was not correlated with starch accumulation. For all genotypes, total sugar accumulation increased between P1 and P4. The results indicated that low P nutrition did not consistently lead to increased starch accumulation in tobacco; rather, the effect depended on the cultivar and/or species.