Yield stimulation of a commonly grown cultivar of Phaseolus vulgaris L. at near‐ambient ozone concentrations

Abstract

SUMMARYSeeds of Phaseolus vulgaris L, cv, Nerina were hand-sown inside open-top chambers (OTCs) in which the plants were exposed to charcoal-filtered air (CF treatment), ambient air (NF), or ambient air with added 6, 12, 18, 25 or 30 nl r^ of ozone (NF6, NF12, NF18, NF25 and NF30 treatments, respectively). Exposure commenced as the crop emerged and continued on a daily basis until the end of the season. Ozone (O3) was added between 10,00 and 18,00 h GMT, The seasonal 7 h mean O3 concentrations ranged from 10 nl I"^ in the CF treatment to 50 nl r ' in the NF30 treatment.The growth and yield of P. vulgaris cv, Nerina demonstrated two distinct responses to O3 depending upon concentration. At seasonal 7 h means of 20, 26 and 32 nl 1"' (NF, NF6 and NFI 2 treatments respectively), the yield increased relative to that of the CF" treatment. The increase in yield peaked at 48% in the NF6 treatment {P < 0-05), and was associated with a 55 % increase in the maximum leaf number, longer retention of the canopy, and a 45 % increase in the number of pods present at the Rnal harvest. In contrast, seasonal 7 h mean O3 concentrations of 38, 45 and 50 nl T' (NFI8, NF25 and NF30 treatments) caused 26^2 "o reductions in the yield of P, vulgaris. The leaves of such plants developed extensive symptoms of O3 injury and were prematurely abscised from the plants. The reductions in yield were due to a decrease in the numbers of seeds per pod and in the weights of individual seeds.

Growth responses of seedlings of sixBetula pubescensEhrh. Provenances to six ozone exposure regimes

“…Plant height was increased by moderate O 3 concentrations (about 40 nmol mol" 1 )-Although growth stimulation caused by O 3 is seldom reported, it has occasionally been observed in response to long-term low-level exposures (Rajput & Ormrod 1986, Sanders et al 1992. Such a stimulation of plant height in birch seems to be dependent on good light conditions, since it was not found in a previous experiment at a similar temperature (Mortensen & Skre 1990).…”

Growth response of grassland species to ozone in relation to soil moisture condition and plant strategy

“…By contrast, no biomass increase has been found in P. lanceolata and C. jacea exposed to similar conditions (Mortensen & Nilsen, 1992). Increased growth at low levels of O $ has been observed in other species, for instance in Sonchus nigrum and S. asper (Bergmann et al, 1995), Phaseolus vulgaris (Sanders et al, 1992), and Cucurbita moschata (Rajput & Ormrod, 1986). The physiological mechanisms involved in such growth stimulations as a response to ambient concentration of O $ remain unclear.…”

Environmental hormesis, a fundamental non-monotonic biological phenomenon with implications in ecotoxicology and environmental safety

“…Note: In one dose-response relationship, the maximum stimulation was lower than 105% (102%) however statistically significant and thus was considered as 105% in the calculations of the magnitude range. Hatus (evergreen) chronically (two growing seasons) exposed to increasing levels of SO 2 gas in open top chambers (OTCs) and theoretically 0 kg ha -1 year -1 soil nitrogen deposition (Yamaguchi et al, 2012); (c) Pot-grown seedlings of F. crenata chronically (two growing seasons) exposed to increasing levels of simulated nitrogen deposition with soil HNO 3 (Izuta et al, 2004); (d) Potfree-grown snap beans seedlings (P. vulgaris L. cv 'GV50') exposed to increasing levels of H 2 S gas for 18 ±2 d (66 hours in total) in rectangular minimum interference chambers when O 3 in atmosphere was either 0 (theoretically) or 72 nmol mol -1 (Coyne and Bingham, 1978); (e) Potgrown seedlings of spring barley (Hordeum vulgare L.) exposed to increasing levels of UV-B rays in phytotron chambers for one week (Kacienė et al, 2015); (f) Pot-grown seedlings of sunflower (Helianthus annuus L. cv Russian Mammoth) exposed to increasing levels of NO 2 in artificially lit growth cabinets for two weeks (Okano et al, 1985); (g) Pot-grown seedlings of barley (H. vulgare cv Hockey) and rape (Brassica napus L. cv Callypso) exposed to increasing levels of SO 2 gas in OTCs for about three months (Weigel et al, 1990); (h) Pot-free-grown seedlings of bean (P. vulgaris L. cv Nerina) exposed to increasing levels of O 3 in OTCs for about three months (Sanders et al, 1992); and (i-j) Pot-free-grown plants of winter barley (H. vulgare L. cv. Sonja) exposed to increasing levels of SO 2 in an open-air exposure system from November to July (McLeod et al, 1988).…”