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Effect of Light Quality and Temperature on Fe 3+ Reduction, and Chlorophyll Concentration in Plants 1
Author(s) -
Brown J. C.,
Cathey H. M.,
Bennett J. H.,
Thimijan R. W.
Publication year - 1979
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1979.00021962007100060029x
Subject(s) - sodium vapor lamp , chlorophyll , chemistry , horticulture , photobiology , fluorescence , lactuca , incandescent light bulb , ornamental plant , botany , biology , optics , physics
Plant species differ in their response to light; some grow best in full sunlight, some in partial shade, and others in full shade. Inside, under growth chamber conditions, cool white fluorescent (CWF) lamps, in combination with supplemental incandescent (Inc) lamps, have been a satisfactory light source. Low pressure sodium (UPS) lamps have also been used. The spectral radiant power curve for the CWF lamps extends from 350 (includes UV and blue) to above 700 nm, whereas the spectral curve for LPS lamps is between 560 to 610 nm (no UV or blue) with no radiation below 550 nm. This study was conducted to determine affect of LPS and CWF lamps, alone and in combination with Inc lamps, on plant growth and reduction of Fe 3+ to Fe 2+ . Lettuce ( Lactuca saliva L. ‘Grand Rapids’), cotton ( Gossypium hirsutum L. ‘M8’) and petunia ( Petunia hybrida Vilm. ‘Pink Cascade’) were grown in environmental control cabinets at 22 and 28 C under LPS or CWF lamps, with and without Inc lamps. Reduction of Fe 3+ to Fe 2+ was determined as Fe 2+ ferrorine [disodium salt of 3‐(2‐pyridyl)‐ 5,6‐bis(4‐phenylsulfonic acid‐l,2,4‐triazine] in solution under all light treatments to determine if chlorophyll concentration in plant tops was related to Fe 3+ reduction in solution. We had observed that cotton was chlorotic under LPS, but not under CWF lamps. Only small amounts of Fe 3+ were reduced to Fe 2+ at wavelengths above 420 nm, and more Fe 3+ was reduced to Fe 2+ in solution under CWF than under LPS lamps. Chlorophyll concentration in lettuce and cotton leaves followed about the same pattern as Fe 3+ reduced to Fe 2+ in solution. Chlorophyll levels were greater in leaves grown under CWF than under LPS lamps, and generally greater in leaves grown at 28 than at 22 C. If we assume that CWF light mediates reduction of Fe 3+ to Fe 2+ in plant foliage as it does in ferric‐ferrozine solutions then it could make Fe 2+ available for biochemical reactions related to chlorophyll synthesis. Petunia did not respond to the light regimes and temperature as did lettuce and cotton.