Cotton carbon exchange, nonstructural carbohydrates, and boron distribution in tissues during development of boron deficiency

Abstract

Abstract An adequate supply of boron (B) is critical for optimal cotton (Gossypium hirsutum L.) growth and yield development. A better understanding of the effect of B deficiency on plant physiology and metabolism will help refine the diagnosis of B deficiency and improve B fertilizer recommendations. Determining B distribution in plant tissues and change in the pattern during growth is fundamental for diagnosis of plant B deficiency. Growth chamber and field studies were conducted in 1999 and 2000 to determine the effects of B deficiency on cotton growth, leaf photosynthesis, and nonstructural carbohydrates. The chamber study mainly investigated changes in leaf blade nonstructural carbohydrate concentrations and plant tissue B content during the development of B deficiency. The field study determined whether soil or foliar supplements of B could improve plant growth, carbon assimilation and translocation, and lint yield. In the growth chamber, B deficiency during the early growth of cotton decreased leaf CO2 exchange rate, increased leaf blade nonstructural carbohydrate concentration, and depressed photosynthate export from leaves to fruits, resulting in increased fruit abscission. Among plant parts, leaf blades had highest B concentration. Leaf blade B content accounted for more than 75% of plant total accumulating B under favorable growth chamber conditions. The critical B level of uppermost fully expanded main-stem leaf blades, which affected plant growth and physiological processes, was about 17–20 mg kg−1 during squaring and fruiting. Under our field study conditions, cotton did not respond to either soil or foliar B application due to sufficient soil B for plant growth (0.2 and 0.3 mg B kg−1 at two study sites). These results will provide useful information for cotton plant B diagnosis and B fertilizer recommendations in cotton production.