Fig 1.
Primary photon counting lens and PMT assembly.
Primary PMT lens configuration with matched achromatic doublet pair lens (f = 40 mm) and mechanical shutter (SHB1T). Single edgepass filters were manually inserted as indicated when used for spectroscopy measurements.
Fig 2.
Spathiphyllum dark-adaptation decay plots.
Nine sample decay plots of dark-adapting Spathiphyllum. Purple curve (and inset) depicts the sample average. Enlarged scale of basal count (1.5–2.0 hrs.) reveals 32 cps after two hours. Average dark count is 5 cps.
Fig 3.
Dark-adaptation decay curve fitting.
Comparison of Spathiphyllum dark-adaptation decay data with double exponential and hyperbolic curve equations. Magenta line is 9 sample average decay data. Figure shows hyperbolic curve most closely approximates the data.
Fig 4.
UPE (300–720 nm) of three Spathiphyllum leaves (A-C) during aerobic dark-adaptation and wounding at room temperature. (A) Plant in original (large) enclosure. (B-C) Plant placed in smaller enclosure. Photo inset shows wounding apparatus (D) with 3.0 mm bamboo skewer a typical leaf with wound site highlighted (E) and enlargement of the wound (F) showing approximate image area.
Fig 5.
Typical hyperbolic and dual post wound exponential decays (in air). (A) Complete fluorescent decay/dark adapt—wounding profile. (B) Enlarged view of wounding data. Note primary and secondary post wound decays. Red curve is 25-point data smoothing for trend visibility.
Fig 6.
Spathiphyllum wounding UPE while under anoxic stress (Nitrogen gas).
Moderate increase in photocounts was observed upon anoxic wounding in leaves (D, F). No increase in counts was observed with leaf (E). 25 point smoothing of curve data was used for data visualization.
Fig 7.
Aerobic pre-wound photocount distributions.
Aerobic photocount observed frequencies vs. Poisson predicted distributions (leaves A-C) of the hyperbolic decay data (last 800 s). Observed photon count frequencies closely approximate a Poisson predicted distribution (μA = 31.25; μB = 22.03 and μC = 12.82).
Fig 8.
Leaf aerobic wounding photocount comparison.
Spathiphyllum wounding in air showing distinct peak, secondary rise & subsequent exponential decays (A, B, D). No secondary exponential decay was observed in leaf B (C). Red curve is 10 point smoothing for trend visualization.
Fig 9.
Aerobic post-wound initial decay analysis (300s).
Leaves A, B, & C photocounts (A-C) with double exponential decay fit line (red). (D-F) Observed photon count frequency vs. Poisson predicted distribution corresponding to each leaf (μA = 85.97; μB = 113.53 and μC = 59.66).
Fig 10.
Aerobic post wound secondary exponential decay.
Leaves A, B, & C photocounts with double exponential decay fit line (red) (A-C). Leaf B (B) did not display a secondary decay peak. Cyan curve in (B) is 10 pt smoothed to highlight the decay profile. Red lines (A, C) reflect double exponential curve fit. (D-F) Observed photon count frequency vs. Poisson predicted distribution for each leaf (μA = 48.55; μB = 64.19 and μC = 25.90).
Fig 11.
Aerobic post wound secondary decay photocount distributions.
Photon count statistics of leaves (A-C) approach a Poissonian distribution upon exponential decay relaxation (last 800 s before closing shutter). (μA = 34.32; μB = 44.06 and μC = 18.90).
Fig 12.
Multiple regression comparison of averaged anaerobic wound data.
Three sample average of anoxic wounding data. N2 gas introduced at 6,700 s; plant wounded 7,200 s, and N2 secured at 8,000 s. The two slopes (red = anoxic, blue = aerobic) differ significantly [F (2, 123) = 416, p = 0.05].
Fig 13.
Anoxic wounding photocount distributions.
(A-C) Photocount statistics of leaf anoxic wound data. Observed photon count frequencies closely approximate a Poisson predicted distribution (μD = 22.10; μE = 15.96 and μF = 21.34).
Fig 14.
Poisson distribution fitness (δ) of leaf wounding and dark count data.
Aerobic wound data surpassed PMT dark counts (2/3 samples). (Δ) Indicates the difference in photocounts from basal—wounding peak and correlates with the degree of divergence from Poisson. Aerobic pre-wound, post-wound end, and anoxic (δ) values show close agreement with a Poisson distribution. (Letters = leaves where indicated).
Fig 15.
Secondary photon counting lens and PMT assembly.
Secondary lens configuration showing matched achromatic doublet pair lens (f = 50 mm) and motorized high speed USB filter wheel (HSFW) used in spectroscopy measurements. Filter wheel inset shows filter type for each position. Only positions 1, 2, 5, 6, 7 and 8 were used for the HSFW spectroscopy measurements.
Fig 16.
Spathiphyllum dark adaptation filter wheel spectral analysis.
Leaf UPE during the first 250 s of dark adaptation in air using various optical filters. Solid black line is the non-normalized, 5-point smoothed adjacent average photocount data. Normalized filter data is overlaid for comparison. The decay trend plot is intentionally interrupted by the filter wheel rotation. The filter rotation sequence included a 5 s open (O) and closed (B) phase before each optical edgepass filter measurement (20 s) to better visualize and account for the filter transitions. Data shows no significant UPE above the noise floor from 393–600 nm. Comparison of the LP600 and LP650 plot data reveals that all of the UPE is > 650 nm as the counts are equivalent. The decreased LP700 count data is attributable to the sharp decline of the cathode’s radiant sensitivity at 700 nm vice the filter’s slightly reduced transmittance and thus is inconclusive.
Fig 17.
Spathiphyllum aerobic wounding filter wheel spectral analysis.
Leaf UPE during the first 200 s of aerobic wounding using various optical filters. Solid black line is the non-normalized, 5-point smoothed adjacent average photocount data. Normalized filter data is overlaid for comparison. Leaf was wounded at 2 hrs (7,200 s). The filter wheel measurement sequence was initiated 60 s after wounding. No UPE was detectable below 600 nm. LP600 and LP650 photocounts are equivalent indicating 100% of observed UPE was > 650nm. The reduced LP700 counts are confounded by the PMT cathode’s reduced sensitivity > 700nm.
Fig 18.
Spathiphyllum in plant enclosure (S). Shown with single filter lens assembly and front panel removed.
Fig 19.
Experiment layout and test equipment.
(A) Overview of lab and dark room. (B) Photon counting experiment set up.
Table 1.
Edgepass filters used for spectral analysis.