Hydraulic, morphological, and anatomical changes over the development of cotton bolls and pedicels leading to boll opening under well-watered and water deficit conditions

The growth, development, and opening of cotton bolls largely determine the yield and quality of cotton plants. However, the hydraulic, morphological and anatomical changes of cotton bolls over this course are unclear. This study investigated the hydraulic properties, xylem structure and function of the cotton boll and the pedicel, and the boll transpiration over the developmental course of bolls under well-watered and water deficit conditions based on hydraulic measurements, dye tracing, boll water uptake, and microscopy. Results revealed that xylem structure and function of the boll and the pedicel were well maintained and bolls had a high transpiration rate during boll dehydration period under both conditions. Water deficit significantly reduced boll number, had no significant effect on the final dry matter content of bolls, and had limited effects on boll transpiration and hydraulic properties of the boll and the pedicel. This study indicates that vascular transport between the parent plant and the boll and boll transpiration were well coupled to ensure dry matter accumulation in the boll and promote boll dehydration.