ARS | Publication request: Whole-photosynthesis and transpiration in field-grown papaya plants

Submitted to: International Symposium on Integrating Canopy, Rootstock and Environmental
Publication Type: Abstract Only
Publication Acceptance Date: August 8, 2008
Publication Date: N/A

Technical Abstract: Papaya (Carica papaya L.) is a principal horticultural crop of tropical and subtropical regions. Knowledge of papaya response to environmental factors provides a scientific basis to develop management strategies to optimize fruit yield and quality. In papaya, the photosynthetic capacity also influences papaya fruit quality. In this research, we measured the whole-plant photosynthesis and transpiration rate in field grown papaya plants (6 months of age, plant leaf area of 3.5 m2 with drip fertigation) using chambers (3,400L) made of transparent (97%) Mylar (Dupont, Wilmington, DE, USA) film. In addition, we measured the relationship between the chamber whole-plant transpiration and whole-plant transpiration measured with sap flow gauges inserted in the trunk of the plants (TDP30, Dynamax, Houston,Texas, USA). For the conditions of the study, [sunny days (maximum PAR=1600umol m-2 s-1), average air temperature of 23 degrees celcius and maximum VPDair 3.5kPa), papaya plants transpired (6:00 am to 17:00 pm) 8.6 L of water/day and assimilated 67g of CO2/day (18.27g of C/day) with a water use efficiency of 3.2 mmol CO2/mol H2O. There was no evidence of heat accumulation in the chambers. The mathematical sap flow model proposed by Reis et al. (2006) using Granier’s coefficient overestimated whole-plant transpiration, but there was a high correlation (R2=0.85) between sap flow rates and instant transpiration measured in the chambers. There was also a high correlation (R2=0.90) between hourly transpiration measured in the whole-plant chamber and the calculated reference evapotranspiration (ET0 mm h-1), which may represent a low cost methodology to estimate papaya water demand. These results are important for irrigation management and drip fertigation in papaya, and can promote greater water and fertilizer use efficiency in commercial plantings.