Photosynthetic responses of muskmelon (Cucumis melo L.) to photon flux density, leaf temperature and CO2 concentration

2003 ◽  
Vol 83 (2) ◽  
pp. 393-399 ◽  
Author(s):  
N. Chen ◽  
Y. Gan ◽  
G. Wang
Keyword(s):  
Flux Density ◽  
Open Field ◽  
Cucumis Melo ◽  
Northwest China ◽  
Leaf Temperature ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Saturation ◽  
Rate Of Increase ◽  
Cucumis Melo L

Two cultivars (Huanghemi and Elizabeth) of muskmelon (Cucumis melo L.) were evaluated to determine the effect of photon flux density (PFD), leaf temperature, and CO,2 concentration on the net photosynthetic rate (Pn). The cultivars were evaluated under open field and solar-heated greenhouse conditions in northwest China. The Pn increased as the PFD increased, and then the rate of increase in Pn declined for Huanghemi and decreased for Elizabeth. Elizabeth registered 22 µmol m-2 s-1 for light compensation and 1127 µmol m-2 s-1 for light saturation, which, respectively, were 50 and 70% of those required by Huanghemi. The Pn increased with increasing leaf temperatures in the range of 9.8 to 50.8°C. The optimum temperature for photosynthesis was 35.3°C for muskmelon grown in open field, 2.4°C (7%) greater than that for muskmelon grown in the greenhouse. At optimal temperatures, the field-grown muskmelon had the Pn of 19.8 µmol m-2 s-1, 30% greater than that for the greenhouse-grown muskmelon. Both cultivars responded positively to CO2 concentrations of below the CO2 saturation points, whereas Huanghemi exhibited greater (51%) Pn and higher (49%) carboxylation efficiency than Elizabeth at optimal CO2 level. The two cultivars exhibited greater photosynthesis in open field than when grown in solar-heated greenhouses, while Elizabeth performed better than Huanghemi when light conditions were poor. Selective use of cultivars with low requirements for light and temperatures will enhance the photosynthesis and productivity of muskmelon grown in solar-heated greenhouses of northwest China. Key words: Light compensation, light saturation, photon flux density, transpiration

Gas Exchange of Four Cassava Cultivars in Relation to Light Intensity

1982 ◽  
Vol 18 (4) ◽  
pp. 375-382 ◽  
Author(s):  
Jairo A. Palta
Keyword(s):  
Gas Exchange ◽  
Light Intensity ◽  
Flux Density ◽  
Direct Effect ◽  
Photosynthetic Rate ◽  
Photosynthetic Apparatus ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Saturation ◽  
Effect Of Light

SUMMARYGas exchange measurements were carried out on four cassava cultivars, M. COL22, M. MEX59, M. COL638, and M. VEN218, under a range of light intensities, to investigate possible differences in photosynthesis and transpiration. Over the range of photon flux density 100–1500 μE m−2 s−1 leaves showed a light saturation response typical of C-3 plants with little increase in photosynthetic rate above 1000–1500 μE m−2 s−1 (200–300 Wm−2 PAR). At light saturation there were significant differences in photosynthetic rates between cultivars, with the highest 10% greater than the lowest. Part of the response could be attributed to increased stomatal aperture, and a greater part to a direct effect of light intensity on the photosynthetic apparatus. Transpiration increased with light intensity levels, but no significant differences were observed between cultivars.

Photon flux density and temperature-dependent responses of photosynthesis and photosystem II performance of apple leaves grown in field conditions

2015 ◽  
Vol 42 (8) ◽  
pp. 782 ◽  
Author(s):  
Dennis H. Greer
Keyword(s):  
Electron Transport ◽  
Flux Density ◽  
Leaf Temperature ◽  
Field Conditions ◽  
Photon Flux ◽  
Photochemical Quenching ◽  
Photon Flux Density ◽  
Temperature Dependent ◽  
Light Responses ◽  
Non Photochemical Quenching

The process of photosynthesis depends on the light, and is modulated by leaf temperature and their interaction is important to understand how climate affects photosynthesis. Photosynthetic and PSII light responses at a range of leaf temperatures were measured on leaves of apple (Malus domestica Borkh. cv. Red Gala) trees growing in field conditions. The objective was to assess the interaction between photon flux density (PFD) and temperature on these processes. Results showed leaf temperature strongly modulated the PFD-dependent response of photosynthesis and PSII performance. An interaction on photosynthesis occurred, with temperature affecting saturated rates as well as PFDs saturating photosynthesis. The efficiency of PSII electron transport (operating and maximum in light) universally declined with increasing PFD but temperature strongly influenced the response. Rates of PSII electron transport at saturating PFDs were affected by temperatures. Both photochemical quenching and non-photochemical quenching also responded strongly to temperature but at high PFDs, photochemical quenching increased linearly with decreasing temperatures while non-photochemical quenching increased curvilinearly with increasing temperatures. Modelling revealed changes in photosynthesis were positively correlated with rates of electron transport. These results greatly enhance our understanding of photosynthesis and the underpinning processes and their responses to temperature and PFD.

scholarly journals Estimation of Global and Diffuse Photosynthetic Photon Flux Density under Various Sky Conditions Using Ground-Based Whole-Sky Images

2019 ◽  
Vol 11 (8) ◽  
pp. 932
Author(s):  
Megumi Yamashita ◽  
Mitsunori Yoshimura
Keyword(s):  
Flux Density ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Diffuse Component ◽  
Photosynthetic Photon Flux ◽  
Physiological Processes ◽  
Sky Conditions ◽  
Mean Square Errors ◽  
Relative Root

A knowledge of photosynthetic photon flux density (PPFD: μmol m−2 s−1) is crucial for understanding plant physiological processes in photosynthesis. The diffuse component of the global PPFD on a short timescale is required for the accurate modeling of photosynthesis. However, because the PPFD is difficult to determine, it is generally estimated from incident solar radiation (SR: W m−2), which is routinely observed worldwide. To estimate the PPFD from the SR, photosynthetically active radiation (PAR: W m−2) is separated from the SR using the PAR fraction (PF; PAR/SR: unitless), and the PAR is then converted into the PPFD using the quanta-to-energy ratio (Q/E: μmol J−1). In this procedure, PF and Q/E are considered constant values; however, it was reported recently that PF and Q/E vary under different sky conditions. Moreover, the diffuse ratio (DR) is needed to distinguish the diffuse component in the global PAR, and it is known that the DR varies depending on sky conditions. Ground-based whole-sky images can be used for sky-condition monitoring, instead of human-eye interpretation. This study developed a methodology for estimating the global and diffuse PPFD using whole-sky images. Sky-condition factors were derived through whole-sky image processing, and the effects of these factors on the PF, the Q/E of global and diffuse PAR, and the DR were examined. We estimated the global and diffuse PPFD with instantaneous values using the sky-condition factors under various sky conditions, based on which the detailed effects of the sky-condition factors on PF, Q/E, and DR were clarified. The results of the PPFD estimations had small bias errors of approximately +0.3% and +3.8% and relative root mean square errors of approximately 27% and 20% for the global and diffuse PPFD, respectively.

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