The Photosynthetic Action Spectrum of the Bean Plant

Abstract

The photosynthetic action spectrum of the bean plant leaf, Phaseolus vulgaris L. (variety Red Kidney), has been determined with a diffraction grating illuminated by a 6500-watt xenon arc. An infrared CO2 analyzer was used to determine the gross photosynthetic rate of the terminal leaflet of the first trifoliate leaf. The rate was measured as a function of the light intensity at steps of 12.5 nanometers which approximates the length of the leaflet used. Twentyfive curves between 400 and 700 nanometers were used to establish the action spectrum. All light curves were some linear function of the incident intensity, and all were extrapolated to zero. The action spectrum shows the follow- Despite the large number of papers published on the action spectra of algae, we have not been able to find one complete reliable action spectrum of a higher plant that has been determined at many different narrow wave length bands. The recent work of Egneus (5) and Lundegardh (13) is of qualitative nature and covers only limited portions of the visible spectrum. Most of the early work was done by using filters that isolate a rather wide band of light. The work of Hoover (11) with such a system has been widely published and furnishes the basis for our present understanding of action spectra for higher plants. It is the purpose of this study to establish the photosynthetic action spectrum for the bean plant leaf, Phaseolus vulgaris L. (variety Red Kidney), with a diffraction grating spectrograph. nutrients, under the following environmental conditions: temperature 23 i 1 C; fluorescent light of spectral distribution shown in Figure 1, of an intensity of 1200 to 1750 ft-c on a 12-hr photoperiod, and a relative humidity of 60 + 5%. The age of the plants used varied between 18 and 21 days from the seed. Only the intact terminal leaflet of the first trifoliate leaf was used. MATERIALS AND METHODSPhotosynthesis was measured by means of an infrared CO2 analyzer (Beckman, L/B, 15 A) in a closed system. It consisted of a Plexiglass leaf chamber, a pump (Randolph Pump, model 500 with a Zero-Max gearhead Q1-Qw55-M52) and a flowmeter. Air was circulated at a constant flow rate of 1.1 liters/min. The air temperature of the chamber was controlled by controlling the ambient temperature. Apparent photosynthesis was determined from the average CO2 uptake during two consecutive 4-to 5-min light exposures at each intensity and wave length. Each CO2 uptake period was followed by an 8-to 10-min dark period, wherein CO2 evolution was measured. The system was flushed with a 500 Al/liter CO2 stream for 1 min between the two sequential determinations. Flushing with standard CO2 whenever the wave length or intensity was changed obviated the use of a drying agent in the closed system and assured against CO2 depletion.The rate of gross photosynthesis was calculated as the absolute sum of the apparent photosynthetic rate and light respiration. The latter was assumed to equal the average dark respiration before and after a light exposure. Two observations...

Plant Physiological Acclimation to Irradiation by Light-Emitting Diodes (Leds)

“…The pattern of growth response to the different NBL treatments approximately resembled the quantum yield for CO 2 fixation along the PAR spectrum found in previous research (e.g. McCree, 1972;Balegh and Biddulph, 1970). The spectrum used had no significant effect on specific leaf weight (SLW, g/cm 2 ; Fig.…”

“…1. Light sensitivity of the human eye along the PAR spectrum (data from http://www.giangrandi.ch/optics/eye/eye.shtml) and quantum yield for CO 2 fixation of a bean leaf (data from Balegh and Biddulph, 1970). .…”

Induction of Phenylalanine Ammonia-lyase in Strawberry Leaf Disks

“…8, lines 4 and 5), indicate DCMU does not inhibit the PAL inactivating system and also indicate the presence of an inactivating system in leaf disks after 36 hr of preincubation. (1) H20 and light; (2) F2O and light and 20 usg/ml cycloheximide; (3) H20 and darkness; and (4) H20 and darkness and 20 /Ag/ml cycloheximide. PAL activity was assayed at intervals as indicated.…”

“…Each point in this plot is an average of nine samples. (2). PAL activity was assayed at intervals as indicated.…”

“…The action spectra for induction and inactivation of PAL were determined with a large spectrograph capable of producing a 16-ft long continuous spectrum. Details of the structure and operation of the spectrograph were described by Balegh and Biddulph (2). Leaf disks used in determining the induction spectrum were cut and injured as described and incubated in 0.…”