Effects of leaf age, nitrogen nutrition and photon flux density on the distribution of nitrogen among leaves of a vine (Ipomoea tricolor Cav.) grown horizontally to avoid mutual shading of leaves

Oecologia ◽  
1994 ◽  
Vol 97 (4) ◽  
pp. 451-457 ◽  
Author(s):  
Kouki Hikosaka ◽  
Ichiro Terashima ◽  
Sakae Katoh

Oecologia ◽  
1998 ◽  
Vol 113 (3) ◽  
pp. 314-324 ◽  
Author(s):  
N. P. R. Anten ◽  
K. Miyazawa ◽  
K. Hikosaka ◽  
H. Nagashima ◽  
T. Hirose




1977 ◽  
Vol 55 (17) ◽  
pp. 2288-2295 ◽  
Author(s):  
M. Aslam ◽  
S. B. Lowe ◽  
L. A. Hunt

The effect of plant and leaf age on CO2-exchange rates (CER) and transpiration rates in 15 genotypes of cassava (Manihot esculenta Crantz) was measured in situ by infrared gas analysis. The plants were grown in a controlled-environment room with a 14-h photoperiod, day–night temperatures of 29–24 °C, and 60–70% relative humidity.Plant age had no effect on leaf CER, whereas transpiration rates in 14-week-old plants were significantly greater than those in 7-week-old plants. Both CER and transpiration rates decreased with leaf age. The decline was negligible when measured at low photosynthetic photon flux density. At saturating light, however, both CER and transpiration rates decreased significantly in most of the genotypes. Significant genotypic differences were observed in the pattern of decline. Both stomatal (rs) and residual (rr) resistances to the diffusion of CO2 increased with leafage in all the genotypes. The relative increase in rr was much greater than the increase in rs. In all the genotypes the ratio rr:rs was greater than unity, suggesting that rr is the major component of the total resistance to photosynthesis. Chlorophyll content and specific leaf weight also varied significantly among the genotypes. However, chlorophyll content decreased and specific leaf weight increased with leaf age.





2019 ◽  
Vol 11 (8) ◽  
pp. 932
Author(s):  
Megumi Yamashita ◽  
Mitsunori Yoshimura

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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