humidity (30 vs. 92%). Light quality has been indicated as a primary factor regulating intumescence development in tomato (Lang and Tibbitts, 1983) and sweetpotato ( Craver, 2014 ), although underlying mechanisms remain poorly understood. Ultraviolet
Tomomi Eguchi, Ricardo Hernández, and Chieri Kubota
Karl N. Nilsen
Although man has effectively accelerated genetic alteration among crop plants in the direction of greater suitability for intensive culture, this has been a comparatively recent and minor genotypic rearrangement as compared to the accumulated contribution of millions of years of prior evolutionary selection. Man's concern with plants has from the beginning been based on their unique photosynthetic capability through which light energy, the ultimate source of life-sustaining free energy, is converted to biologically available chemical energy. In addition, light has been a primary environmental factor within the total regime of selection pressures which have shaped the morphogenic character of plants. It is permissable to anticipate terrestrial plants as responsive in a variety of ways (many yet undescribed) to all wavelength regions of the earth-impinging solar irradiance spectrum. This could be especially true within the shorter wavelength regions (ultraviolet) due to greater photon energies enabling greater possible photochemical and thus greater photobiological activity (39). With the foregoing in mind, how do common light sources vary and is this of any consequence?
Barbara J. Smith, Amir Rezazadeh, Eric T. Stafne, and Hamidou F. Sakhanokho
, Wilmington, MA), and WSF+UV-B (UV-B, Philips Broadband Ultraviolet-B TL 20W/12 RS, Hamburg, Germany) were suspended ≈1.2 m above strawberry plants. The light intensity adjustment of the adjustable spectrum LumiGrow Pro 325 LED grow lights was used to set the
C. Stevens, C. L. Wilson, J. Y. Lu, V. A. Khan, E. Chalutz, M. K. Kabwe, Z. Haung, S. Droby, and L. Pusey
Low doses of ultraviolet light (254nm UV–C) irradiation reduced postharvest rots of pome, stone and citrus fruits. Brown rot (Monilinia fructicola) of `Elberta' and `Loring' peaches was significantly reduced by UV–C. Alternaria rot (Alternaria spp.) and bitter rot (Colletotrichum spp.) the principal storage rots of `Golden Delicious apples showed significant reduction following UV–C treatment. Further application of UV–C was effective in controlling green mold rot (Penicillium digitatum) of `Dancy' Tangerines and `Marsh Seedless' grapefruits, stem end rot (Alternaria citri), as well as sour rot (Geotrichum candidum) of `Dancy' tangerines after irradiation.
J. Liu, C. Stevens, V.A. Khan, J.Y. Lu, C.L. Wilson, O. Adeyeye, M.K. Kabwe, L. Pusey, E. Chalutz, T. Sultana, and S. Droby
The application of low hormetic low-dose ultraviolet light (WV-C, 254 nm) on fruits and vegetables to stimulate beneficial responses is a new method for controlling storage rots and extending the shelf-life of fruits and vegetables. The present study was aimed at treating tomatoes (lycopersicon esculentum) with different UV-C dosages (1.3 to 40 KJ/m2) to induce resistance to black mold (Alternaria alternata), gray mold (Boytris cinerea), and Rhizopus soft rot (Rhizopus stolonifer). Thesediseases were effectively reduced when tomatoes were artificially inoculated following UV-C irradiation UV-C treated tomatoes were firmer in texture and less red in color than the control tomatoes, indicating a delay in ripening. Slower ripening and resistsace to storage rots of tomatoes are probably related. The positive effect of UVC on tomatoes decreased as treatments were performed at stages of increased ripeness.
C. Stevens, P. L. Pusey, V. A. Khan, J. Y. Lu, C. L. Wilson, E. Chalutz, M. K. Kabwe, Z. Haung, O. Adeyeye, and J. Lin
Low hormetic doses of ultraviolet light (UV-C) stress on exposed peaches (Prunus persica). reduced brown rot resulting from field and artificial inoculation from Monilinia fructicola. To test the hypothesis that UV-C induced resistance through host responses the following tests involving biochemical changes (phenlyalanine ammonia-lyase activity (PAL) and ethylene production (EP)), bioassay of antifungal activity of tissue extracts to the fungus, and latent infection of rot free peaches previously treated with and without UV-C were determined. Exposure of peaches to UV-C dose of 7.5×104 ergs/mm2 promoted an increase in PAL and EP compared to the control. As the PAL activity increased, percent storage rots decreased. Antifungal activity to the fungal conidia in UV-C treated peach extract showed that the percent conidia germination was reduced 3 folds. Preharvest infection of brown rot which indicated latent infection was significantly reduced. To test for the germicidal effect of UV-C on M. fructicola on the surface of peaches, an artificial epiphytic population of the fungus was deposited on the peaches. A negative relationship between UV-C dose of 1.3 to 40×104 ergs /mm2, colony forming units and number of decaying brown rot lesions were found.
Fouad M. Basiouny and R. H. Biggs
Effects of UV-B radiation (280-310 nm) and Zn deficiency on photosynthesis and carbonic anhydrase (CA) activity in peach seedlings (Prunus persica (L.) Batsch) were studied. Low Zn markedly reduced CA activity; however, the reduction was not proportional to the reduction in leaf Zn content. Zn-deficient leaves irradiated with UV-B had lower CA activity, chlorophyll content, spectral reflectance and rates of photosynthesis. The reduction was more pronounced when leaves were distinctly chlorotic. Higher CA activity was not necessary for maintaining high rates of photosynthesis. Target areas in the leaf for UV-B absorption are discussed.
Abby Pace, Bruce L. Dunn, and Charles Fontanier
, Cupertino, CA). Images were collected before black light exposure (flower mean without ultraviolet) and again while a 365-nm black light was used (Sunlite Industrial Corp., El Monte, CA); the results were reported as the flower mean with ultraviolet light
Heidi C. Anderson, Mary A. Rogers, and Emily E. Hoover
selectively block or absorb wavelengths of light in the IR or ultraviolet ranges, or diffuse incoming direct beam solar radiation without inhibiting necessary transmission of photosynthetically active radiation ( PAR ). PAR includes both visible light and
Edward J. Nangle, David S. Gardner, James D. Metzger, Dominic P. Petrella, Tom K. Danneberger, Luis Rodriguez-Saona, and John L. Cisar
−1 ) combined with UV-B (0.09 mol·m −2 ·d −1 ) treatments led to a decrease in leaf area of 47% and a decrease in leaf dry weight of ≈25% ( Cen and Bornman, 1990 ). Ultraviolet light exposure can reduce photosynthesis by 30% due to direct damage to