Whole-canopy photosynthesis and transpiration in field-grown papaya plants

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 influen...

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Bibliographic Details
Published inActa horticulturae no. 9032; pp. 1169 - 1174
Main Authors Ferraz, T.M, Campostrini, E, Torres-Netto, A, Reis, F.O, Sousa, E.F. de, Glenn, D.M
Format Journal Article
LanguageEnglish
Published International Society for Horticultural Science 2011
Subjects
air temperature
canopy
carbon dioxide
Carica papaya
environmental factors
fertigation
fruit quality
fruit yield
gauges
heat
horticultural crops
leaf area
papayas
photosynthesis
photosynthetically active radiation
sap flow
subtropics
transmittance
transpiration
water use efficiency
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Summary: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. We measured the whole-canopy net CO2 exchange and transpiration rate in field grown papaya plants (5 months of age, plant leaf area of 3.5 m2 with drip fertigation) using whole-canopy chambers (3,400 L) of Mylar film (97% transmittance PAR). In addition, we measured the relationship between whole-canopy transpiration rate measured with the chamber and measured with the temperature difference between sap flow gauges inserted in the trunk of the plants using the Granier heat coefficient (K). For the conditions of the study, [sunny days (maximum PAR=1,600 µmol m-2 s-1), average air temperature of 23°C and maximum VPDair 3.5 kPa], papaya plants transpired 8.6 L of water/day (8:00 am to 17:00 pm) and assimilated 67 g of CO2/day (18.27 g 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) (forced-flow through a stem section) overestimated whole-canopy transpiration but there was a high correlation (R2=0.85) between K and instant whole-canopy transpiration rate measured in the chambers for the data measured after 12:00. However, there was a morning lag phase in sap flow. There was also a high correlation (R2=0.89) between hourly transpiration rate measured in the whole canopy chambers and the calculated reference evapotranspiration (ET0 mm h-1), which may represent a low cost methodology to estimate papaya water demand.
ISSN:0567-7572