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.

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

Effects of photon flux density on photosynthesis, growth, flowering, and oil content in Boronia

1998 ◽  
Vol 49 (5) ◽  
pp. 791 ◽  
Author(s):  
J. M. Wann ◽  
R. Orifici ◽  
Z. E. Spadek ◽  
J. A. Plummer
Keyword(s):  
Light Intensity ◽  
Flux Density ◽  
Oil Content ◽  
Natural Habitat ◽  
Volatile Oil ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Cut Flowers ◽  
Eucalyptus Marginata ◽  
Full Sunlight

Boronia heterophylla is cultivated for cut flowers and B. megastigma for volatile oil production. Both species are endemic to south-western Western Australia and their natural habitat is often shaded by a canopy of Melaleuca parviflora or Eucalyptus marginata. Shade tents were used to examine the influence of reduced photon flux density (PFD) on photosynthesis, growth, and flower production in B. heterophylla and B. megastigma. Volatile oil content was also examined in B. megastigma. Photosynthesis in field-grown B. heterophylla was saturated at 16·2 µmol CO2/m 2·s under a PFD of 1022 µmol/m 2·s (75% full sunlight). Flower number was highest under 75% full sunlight but the number of harvestable stems was the same under 75% and full sunlight. More flowers were produced by B. megastigma plants grown under 75% full sunlight. Content of α-pinene and limonene decreased with decreasing light intensity, whereas β-ionone and docecyl acetate increased with decreasing light intensity

Intra-Leaf Gradient of Assimilation Rate and Optimal Allocation of Canopy Nitrogen: a Model on the Implications of the Use of Homogeneous Assimilation Functions.

1995 ◽  
Vol 22 (3) ◽  
pp. 425 ◽  
Author(s):  
FW Badeck
Keyword(s):  
Flux Density ◽  
Nitrogen Availability ◽  
Optimal Allocation ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Photosynthetic Photon Flux ◽  
Allocation Pattern ◽  
Experimental Findings

A model on the allocation of nitrogen available for the construction of photosynthetic apparatus in leaves in different morphological positions is presented. The allocation pattern is calculated under the assumption that nitrogen distribution is optimised in order to maximise daily whole-plant assimilation. The solution is fairly sensitive to the assimilation function applied. It is shown that assimilation functions homogeneous in irradiance and nitrogen imply assimilation gradients and light-saturation characteristics of the whole canopy which contradict experimental findings. An equation for the calculation of electron transport rates as a function of the intra-leaf gradient of the photosynthetic photon flux density is presented. This inhomogeneous assimilation function leads to substantially different predictions of nitrogen allocation which reproduce a wider array of observed allocation patterns. The results presented in this paper support the thesis that the intra-leaf gradient of photosynthetic photon flux density and self-shading of the thylakoids need to be considered if the assimilation flux is to be modelled as a function of light as well as nitrogen availability on a mechanistic basis.

scholarly journals Effect of Light Quality with Different Red/Far-red Photon Flux Density Ratio on Elongation of Pak-choi Seedlings Grown under High Temperatures.

2001 ◽  
Vol 70 (6) ◽  
pp. 774-776 ◽  
Author(s):  
Tatsuya Hayashida ◽  
Yasushi Shibato ◽  
Yuji Hamachi ◽  
Youichi Yamato ◽  
Hiroko Yamazaki ◽  
...  
Keyword(s):  
Flux Density ◽  
High Temperatures ◽  
Light Quality ◽  
Density Ratio ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Pak Choi ◽  
Effect Of Light

Gas Exchange of Field-Grown Pinus radiata - Relationships With Foliar Nutrition and Water Potential, and With Climatic Variables

1995 ◽  
Vol 22 (6) ◽  
pp. 1015 ◽  
Author(s):  
DW Sheriff
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Flux Density ◽  
Pinus Radiata ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Photosynthetic Photon Flux

Gas exchange measurements were conducted on Pinus radiata to investigate relationships between these and leaf-air vapour pressure deficit, photosynthetic photon flux density, and foliar temperature, water potential and nutrition in the field. Multiple non-linear regressions indicated strong relationships between gas exchange and foliar [P] (but of no other nutrient), leaf-air vapour pressure deficit, photosynthetic photon flux density, foliar water potential and temperature. The final regression produced for relationships between gas exchange and these variables explained 81% of the variance in the data. Micro-climate and foliar data from another site were used to predict gas exchange using the regressions and calculated parameters. Good agreement was obtained between the predicted values and carbon assimilation measured at that site. The relationship was poorer for leaf conductance.

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