Sweet corn (Zea mays L.) varieties carrying the sh2 gene are in high demand, but such varieties have poor stress tolerance, especially during plant establishment. Trichoderma harzianum Rifai strain 1295-22 is a biocontrol fungus developed to provide season-long colonization of crop roots. It has the potential to reduce root rot and increase root growth. In the absence of detectable disease, colonization by Trichoderma increased root and shoot growth by an average of 66%. The enhancement was not uniform among the plants. Low- and intermediate-vigor plants were larger in the presence of Trichoderma, but high-vigor plants were not further enhanced by the fungus. Seeds that were subjected to oxidative stress with 0.05% NaOCI had much-reduced vigor; subsequent treatment with Trichoderma fully restored vigor. This result indicates that the damage caused by hypochlorite is specifically repaired by Trichoderma. Treatment of imbibed but unemerged seeds with cold (5/10 °C night/day) for varying periods reduced subsequent growth. Plants with Trichoderma-colonized roots were 70% larger at all durations of cold treatment. The absence of interation indicates the growth reduction due to cold and the growth enhancement due to Trichoderma are by different mechanisms. Allelopathic reduction in root growth by rye was mimicked by applying benzoxazolinone to the soil. Trichoderma-colonized roots grew faster, but the characteristic shortening of the radicle still occurred. There was no interaction between Trichoderma and allelopathy, indicating that these two treatments affect growth by independent mechanisms. The different ways that growth was enhanced by Trichoderma lead us to propose that this fungus acts, in part, by reversing injurious oxidation of lipids and membrane proteins. Root growth is markedly enhanced by colonization with Trichoderma harzianum. This enhancement can restore some stress-induced growth reduction and may directly reverse oxidative injury.
Average global surface temperatures are predicted to rise due to increasing atmospheric CO2 and other greenhouse gases. Attempts to predict plant response to CO2 must take into account possible temperature effects on phenology and reproductive sink capacity for carbohydrates. In this study, we investigated the effects of atmospheric CO2 partial pressure [35 Pa ambient CO2 (aCO2) vs. 70 Pa elevated CO2 (eCO2)] and temperature (26/15 vs. 35/21 °C day/night) on short- and long-term net CO2 assimilation (An) and growth of red kidney bean (Phaseolus vulgaris). During early vegetative development [14-31 days after planting (DAP)], An, and relative growth rate (RGR) at eCO2 were significantly greater at the supra-optimum (35/21 °C) than at the optimum (26/15 °C) temperature. At 24 DAP, the CO2 stimulation of An by eCO2 was 49% and 89% at optimum and supra-optimum temperature, respectively, and growth enhancement was 48% and 72% relative to plants grown at aCO2. This high temperature-induced growth enhancement was accompanied by an up-regulation of An of eCO2-grown plants. In contrast, during later reproductive stages (31-68 DAP) the eCO2 stimulation of An was significantly less at the supra-optimum than at optimum temperature. This was associated with reduced seed set, greater leaf carbohydrate accumulation, and down-regulation of An at the higher temperature. At final harvest (68 DAP), the eCO2 stimulation of total dry weight was 31% and 14% at optimum and supra-optimum temperature respectively, and eCO2 stimulation of seed dry weight was 39% and -18% at optimum and supra-optimum temperature, respectively. These data indicate substantial shifts in the response to eCO2 during different phenological stages, and suggest that impaired reproductive development at high temperature could reduce the potential for CO2 stimulation of photosynthesis and productivity in bean and possibly other heat-sensitive species.
A 12-week greenhouse experiment was undertaken to test the efficiency of inoculation of vesicular-arbuscular mycorrhizal fungi on four apple (Malus domestica Borkh) rootstock cultivars: M.26, Ottawa 3 (Ott.3), P.16, and P.22. The plants were grown in soil from an apple rootstock nursery, containing high levels of extractable P (644 kg Bray/1 ha-1). Inoculation treatments were Glomus aggregatum Shenck and Smith emend. Koske, G. intraradix Shenck and Smith, and two isolates of G. versiforme (Karsten) Berch, one originally from California (CAL) and the other one from Oregon (OR). Mycorrhizal plants were taller, produced more biomass, and had a higher leaf P concentration than the uninoculated control plants. Mycorrhizal inoculation also significantly increased the leaf surface area of `M.26' and `Ott.3' compared to the control. Glomus versiforme(CAL)-inoculated plants generally had the best nutrient balance, the greatest final height and shoot biomass, and produced an extensive hyphal network. All the mycorrhizal plants had similar percentages of root colonization, but the size of the external hyphal network varied with fungal species. Glomus versiforme(OR) had a larger extramatrical phase than G. aggregatum and G. intraradix. Mycorrhizal efficiency was associated with a larger external hyphal network, but showed no relation with internal colonization. Despite the high P fertility of the soil used, growth enhancement due to mycorrhizal inoculation was attributed to improved P nutrition.
Belowground positive and negative feedbacks on CO 2 growth enhancement Plant Soil 187 119 131 Cardon, Z.G. 1996 Influence of rhizodeposition under elevated CO 2 on plant nutrition and soil organic matter Plant Soil 187 277 288 Curl, E.A. Truelove, B. 1986
. Yousaf, S. Pastar, M. Afzal, M. Sessitsch, A. 2014 The endophyte Enterobacter sp. FD17: A maize growth enhancer selected based on rigorous testing of plant beneficial traits and colonization characteristics Biol. Fertil. Soils 50 249 262 Penrose, D
The establishment and performance of vesicular–arbuscular mycorrhizae (VAM) formed by Glomus fasciculatum (Thaxter) Gerd. & Trappe were studied on geranium (Pelargonium × hortorum L.H. Bailey) and subterranean clover (Trifolium subterraneum L.) in various growth media at 2 P fertility levels. Colonization by G. fasciculatum was not extensive and shoot dry weight and P uptake consequently were not increased by VAM in soilless media such as peat, bark, perlite, and vermiculite. In media containing soil and fertilized at the low P level, roots were colonized extensively by G. fasciculatum, and host shoot growth and P concentrations were increased by VAM. Host growth enhancement by VAM was not observed at the higher P fertility level. Differences in colonization and mycorrhizal response in different fertilized growth media were correlated negatively with the logarithm of the equilibrium solution P concentration. Colonization, growth response, and P uptake by geranium inoculated with G. mosseae (Nic. & Gerd.) Gerd. & Trappe or Acaulospora spinosa Walker & Trappe were affected by growth medium and P fertilizer in the same way as plants inoculated with G. fasciculatum. Peat mosses from different sources varied considerably in their effects on mycorrhiza formation by G. fasciculatum, and on growth response of geranium when the peat was diluted with different amounts of soil. These differences appeared to be related to the equilibrium solution P concentration of the fertilized peats, and not to extractable P of the unfertilized peats. Use of rock phosphate or bonemeal instead of NaH2PO4 as a source of P did not improve the establishment of VAM and host growth response in soil, peat, or vermiculite. Addition of 5–10% Turface, bentonite, silt loam soil, or clay subsoil to peat or vermiculite resulted in increased colonization of host roots and significant mycorrhizal growth response, whereas amendment with liquid sludge inhibited formation of mycorrhizae.
2016 and 116% in Fall 2017. These results suggest that nighttime O 3 may have stimulated the productivity of R123. Agathokleous et al. (2019a) showed that O 3 can induce nonlinear responses with an initial growth enhancement known as hormesis. The