Soybean Growth Responses to Enhanced Levels of Ultraviolet‐b Radiation Under Greenhouse Conditions

Abstract

Soybean (Glycine max [L.] Merr. cv. Essex) was grown in an unshaded greenhouse under three levels of biologically effective ultraviolet‐B (UV‐BBE) radiation (effective daily dose: 0, 11.5 and 13.6 kJ m–2) for 91 days. Plants were harvested at regular intervals beginning 10 days after germination until reproductive maturity. Mathematical growth analysis revealed that the effects of UV‐B radiation varied with plant growth stage. The transition period between vegetative and reproductive growth was the most sensitive to UV‐B radiation. Intermediate levels of UV‐B had deleterious effects on plant height, leaf area, and total plant dry weight at late vegetative and reproductive stages of development. Specific leaf weight increased during vegetative growth but was unaffected by UV‐B during reproductive growth stages. Relative growth, net assimilation, and stem elongation rates were decreased by UV‐B radiation during vegetative and early reproductive growth stages. Variation in plant responses may be due in part to changes in microclimate within the plant canopy or to differences in repair or protection mechanisms at differing developmental stages.

Growth and production of buckwheat (Fagopyrum esculentum) treated with reduced, ambient, and enhanced UV-B radiation

“…The most sensitive time for developing plants is the transition from vegetative to reproductive phase [31]. Successful reproduction is an important aspect in agricultural plants.…”

A Method for Evaluation of UV and Biologically Effective Exposures to Plants

“…Murali et al (4) and Teramura and Sullivan (2) measured an ambient daily UVBE exposure of 11.5 kJ m -2 using the generalised plant response action spectrum with the UV lamps at a height of 0.75 m. This present research employed an average ambient daily UVBE of 3.5 kJ m -2 or alternatively an average daily UVBE of 2.0 kJ m -2 to the individual plant canopy. This difference in ambient exposure is due mainly to the thickness of 0.08 mm of the CA filter material in the studies in the literature (2,4) and this study employing a thickness of 0.13 mm.…”

“…Murali et al (4) did not measure plant height but found reductions in leaf area and total plant dry mass of 19 and 17% respectively at the V6 stage for Essex soybean. Teramura and Sullivan (2) measured plant height at the V4 stage for Essex soybean and found no statistically significant difference. These differences in results may be related to differences in the studies in the literature compared to this research, firstly in levels of UV exposure and secondly in microclimate conditions including the levels of photosynthetically active radiation which influences the UVB sensitivity of plants (2,3) .…”

“…A number of studies (1,2) have reported that UV effects on plants are dependent on the exposure levels. Consequently, a more accurate measure of the UV exposure to the plant canopy is required.…”

“…This cultivar is not normally grown in Australia, but is popular in the USA and previous greenhouse (2,3,4) and field studies (5) have shown it to be sensitive to UVB radiation.…”