Photosynthetic responses and acclimation of two castor bean cultivars to repeated drying–wetting cycles

Abstract

To investigate the responses of castor bean to repeated drying–wetting cycles (RDWC), morpho-physiological parameters of two cultivars (Jiaxiang 2 and Hangbi 8) were determined by a pot experiment under well-watered control and RDWC. RDWC inhibited plant growth and leaf development, decreased water loss rate (WLR), and enhanced leaf mass per area (LMA) and chlorophyll content as indicated by spectral reflectance indices for both cultivars. Photosynthesis was inhibited by progressive drought stress but quickly recovered after rewatering for each cycle. Both cultivars exhibit a similar pattern of acclimation to RDWC: (1) higher LMA and lower WLR, (2) increased photosynthetic capacity under drought stress with increasing cycle numbers, (3) quick recovery and over-compensation for photosynthesis after rewatering, and (4) increased chlorophyll content. Jiaxiang 2 shows a high capacity for water preservation under drought stress and an over-compensation for photosynthesis after rewatering compared with Hangbi 8.

Keywords:

• Ricinus communis L.
• repeated drying–wetting cycles
• cultivar difference
• morpho-physiological responses
• acclimation

Acknowledgments

The authors are thankful to the Opening Foundation of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau for providing financial assistance to the work through the research group project No. 10501-277.