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Title: Photosynthesis, growth, and ultraviolet irradiance absorbance of Cucurbita pepo L. leaves exposed to ultraviolet-B radiation (280 to 315 nm)

Abstract

Net photosynthesis, growth, and ultraviolet (uv) radiation absorbance were determined for the first leaf of Cucurbita pepo L. exposed to two levels of uv-B irradiation and a uv-B radiation-free control treatment. Absorbance by extracted flavonoid pigments and other uv-B radiation-absorbing compounds from the first leaves increased with time and level of uv-B radiation impinging on leaf surfaces. Although absorbance of uv-B radiation by extracted pigments increased substantially, uv-B radiation attenuation apparently was insufficient to protect completely the photosynthetic apparatus or leaf growth processes. Leaf expansion was repressed by daily exposure to 1365 Joules per meter per day of biologically effective uv-B radiation by not by exposure to 660 Joules per meter per day. Photosynthesis measured through ontogenesis of the first leaf was depressed by both uv-B radiation treatments. Repression of photosynthesis by uv-B radiation was especially evident during the ontogenetic period of maximum photosynthetic activity.

Authors:
Publication Date:
Research Org.:
New Mexico State Univ., Las Cruces
OSTI Identifier:
6637908
Resource Type:
Journal Article
Resource Relation:
Journal Name: Plant Physiol.; (United States); Journal Volume: 67:1
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; LEAVES; RADIOSENSITIVITY; PHOTOSYNTHESIS; ULTRAVIOLET RADIATION; ATTENUATION; BIOLOGICAL RADIATION EFFECTS; DAILY VARIATIONS; DATA; DOSE-RESPONSE RELATIONSHIPS; OZONE; PIGMENTS; PLANT GROWTH; PLANTS; QUANTITY RATIO; RADIATION DOSES; TIME DEPENDENCE; BIOLOGICAL EFFECTS; CHEMICAL REACTIONS; DOSES; ELECTROMAGNETIC RADIATION; GROWTH; INFORMATION; PHOTOCHEMICAL REACTIONS; RADIATION EFFECTS; RADIATIONS; SYNTHESIS; VARIATIONS 560141* -- Radiation Effects on Plants-- Basic Studies-- (-1987)

Citation Formats

Sisson, W.B. Photosynthesis, growth, and ultraviolet irradiance absorbance of Cucurbita pepo L. leaves exposed to ultraviolet-B radiation (280 to 315 nm). United States: N. p., 1981. Web. doi:10.1104/pp.67.1.120.
Sisson, W.B. Photosynthesis, growth, and ultraviolet irradiance absorbance of Cucurbita pepo L. leaves exposed to ultraviolet-B radiation (280 to 315 nm). United States. doi:10.1104/pp.67.1.120.
Sisson, W.B. 1981. "Photosynthesis, growth, and ultraviolet irradiance absorbance of Cucurbita pepo L. leaves exposed to ultraviolet-B radiation (280 to 315 nm)". United States. doi:10.1104/pp.67.1.120.
@article{osti_6637908,
title = {Photosynthesis, growth, and ultraviolet irradiance absorbance of Cucurbita pepo L. leaves exposed to ultraviolet-B radiation (280 to 315 nm)},
author = {Sisson, W.B.},
abstractNote = {Net photosynthesis, growth, and ultraviolet (uv) radiation absorbance were determined for the first leaf of Cucurbita pepo L. exposed to two levels of uv-B irradiation and a uv-B radiation-free control treatment. Absorbance by extracted flavonoid pigments and other uv-B radiation-absorbing compounds from the first leaves increased with time and level of uv-B radiation impinging on leaf surfaces. Although absorbance of uv-B radiation by extracted pigments increased substantially, uv-B radiation attenuation apparently was insufficient to protect completely the photosynthetic apparatus or leaf growth processes. Leaf expansion was repressed by daily exposure to 1365 Joules per meter per day of biologically effective uv-B radiation by not by exposure to 660 Joules per meter per day. Photosynthesis measured through ontogenesis of the first leaf was depressed by both uv-B radiation treatments. Repression of photosynthesis by uv-B radiation was especially evident during the ontogenetic period of maximum photosynthetic activity.},
doi = {10.1104/pp.67.1.120},
journal = {Plant Physiol.; (United States)},
number = ,
volume = 67:1,
place = {United States},
year = 1981,
month = 1
}
  • Net photosynthesis, dark respiration, and growth of Rumex patientia L. exposed to a ultraviolet irradiance (288-315 nanometers) simulating a 0.18 atm cm stratospheric ozone column were determined. The ultraviolet irradiance corresponding to this 38% ozone decrease from normal was shown to be an effective inhibitor of photosynthesis and leaf growth. The repressive action on photosynthesis accumulated through time whereas leaf growth was retarded only during the initial few days of exposure. Small increases in dark respiration rates occurred but did not continue to increase with longer exposure periods. A reduction in total plant dry weight and leaf area of approximatelymore » 50% occurred after 22 days of treatment, whereas chlorophyll concentrations remained unaltered. 29 references, 7 figures, 1 table.« less
  • This research was conducted as part of the federal interagency Biological and Climatic Effects Research (BACER) Program established to corroborate research findings related to UV-B radiation effects on plants and to expand the available data base. Ultraviolet B (UV-B, 280-320 nm) radiation effects on gas diffusion through the upper (more exposed) vs. lower leaf surfaces of two snap bean varieties (Phaseolus vulgaris L. Bush Blue Lake 290 (BBL 290) and Astro) were compared. The bean plants were grown under greenhouse and growth chamber conditions, and irradiated for 4 weeks (6 hours/day) to 10 mW m/sup -2/ of biologically effective UVmore » (BEUV) radiation. Diffusive resistances of the upper (r/sub u/) and lower (r/sub l/) surfaces were determined at semi-weekly intervals. A distribution of mean r/sub u//r/sub l/ ratios vs. total leaf resistance (R) was plotted. Ultraviolet-B treatment appeared to increase r/sub u//r/sub l/ ratios only in BBL 290 leaves with R < 2 sec cm/sup -1/ and R > 6 sec cm/sup -1/. Chamber-grown plants were more susceptible to UV-B-induced visible injury than were greenhouse plants. In addition, selected soybean (Glycine max (L.) Merr. York), cotton (Gossyplum hirsutum L. Gregg), cucumber (Cucumis sativus L. Poinsett), clover (Trifolium pratense L. Pennscott), and wheat (Triticum aestivum L. Monon) varieties as well as BBL 290 snap bean were given extended greenhouse exposures ranging from 2 to 6 weeks (6 hours day/sup -1/) to 5-25 m W m/sup -2/ BEUV. Foliar effects on CO/sub 2/ exchange rates (CER) of leaves irradiated throughout the expansion stage and on whole plant biomass production were compared with exposures producing visible injury. Threshold exposure doses required to depress CER and reduce plant dry matter correlated closely with those causing incipient visible injury.« less
  • The expression of ascorbic acid oxidase was studied in zuchini squash (Cucurbita pepo L.), one of the most abundant natural sources of the enzyme. In the developing fruit, specific activity of ascorbic acid oxidase was highest between 4 and 6 days after anthesis. Protein and mRNA levels followed the same trend as enzyme activity. Highest growth rate of the fruit occurred before 6 days after anthesis. Within a given fruit, ascorbic acid oxidase activity was higher in young leaves, and very low in old leaves. Within a given leaf, enzyme activity was highest in the fast-growing region (approximately the lowermore » third of the blade), and lowest in the central placental region. In leaf tissue, ascorbic acid oxidase activity was higher in young leaves, and very low in old leaves. Within a given leaf, enzyme activity was highest in the fast-growing region (approximately the lower third of the blade), and lowest in the slow-growing region (near leaf apex). High expression of ascorbic acid oxidase at a stage when rapid growth is occurring (in both fruits and leaves), and localization of the enzyme in the fruit epidermis, where cells are under greatest tension during rapid growth in girth, suggest that ascorbic acid oxidase might be involved in reorganization of the cell wall to allow for expansion. Based on the known chemistry of dehydroascorbic acid, the end product of the ascorbic acid oxidase-catalyzed reaction, the authors have proposed several hypotheses to explain how dehydroascorbic acid might cause cell wall loosening.« less