Thermal stress events threaten coral populations by disrupting symbiosis between the coral animal and microalgal symbionts in its tissues. These symbionts are key players in the response of the coral holobiont to elevated temperature. However, little is known about the microalgal symbiont type in select corals in the north-western Philippines and how they contribute to the differential responses of coral species. Based on sequencing of major ITS2 bands from DGGE, the dominant algal symbiont in Acropora digitifera, A. millepora, A. tenuis and Favites colemani was identified to be closely related to ITS2 type C3u, Montipora digitata contained ITS2 type C15, and Seriatopora caliendrum hosted ITS2 types similar to C3-Gulf and D1. Thin branching corals, such as A. tenuis and S. caliendrum, exhibited the greatest reduction in photochemical efficiency (Fv/Fm) and symbiont density at elevated temperature, followed by M. digitata and A. millepora, to a lesser extent. A. digitifera and F. colemani were least affected by the temperature treatment. Reduction in Fv/Fm and symbiont density was more apparent in A. tenuis and A. millepora than in M. digitata and F. colemani, although these species all host ITS2 type C3u symbionts. These results suggest that the impact of elevated temperature is influenced by factors apart from symbiont type. This highlights the importance of further studies on the diversity of corals and their microalgal symbionts in the region to gain insights into their potential resilience to recurring thermal stress events.

Glyphosate is regularly used to control annual bluegrass populations indormant bermudagrass turf. A population of annual bluegrass not controlledby glyphosate at 840 g ha−1 (glyphosate resistant, GR) wasidentified on a golf course in Humboldt, TN in 2010. Mature tillers of GRplants were established in a greenhouse and treated with glyphosate at 0,210, 420, 840, 1,680, 3,360, and 6,720 g ha−1. Mature tillers ofa biotype known to be susceptible to glyphosate (SS) were also establishedin the greenhouse and subjected to the same treatments. At 14 d aftertreatment (DAT), glyphosate controlled the SS biotype > 95% at rates >420 g ha−1. Comparatively, the GR biotype was only controlled 76%with glyphosate at 6,720 g ha−1. The rates required to provide50% control (I50 values) for SS and GR biotypes were 236 and 2,812 g ha−1 respectively, resulting in a resistance factor of 12.Photochemical efficiency (Fv/Fm) values on SS plants treated with glyphosate at > 210 g ha−1 measured 0.000 at 14 DAT, whereas Fv/Fm values on GR plants were not significantly different from theuntreated control with glyphosate rates ≤ 840 g ha−1 on the samedate. In laboratory experiments, the SS biotype accumulated greatershikimate concentrations than the GR biotype 3 to 6 DAT. Future researchshould evaluate strategies for managing GR and SS annual bluegrass withalternative modes of action.

Much research has been conducted on mesotrione activity on crops and weeds, but information is lacking in regards to the relative contribution of soil and foliar absorption of mesotrione. Three experiments conducted at Virginia Tech's Glade Road Research Facility in Blacksburg, VA, evaluated the effects of 50 and 90% relative humidity (RH) on the activity of mesotrione applied to foliage, soil, and soil plus foliage. Tall fescue injury ranged from 0 to 21% and was significant in 6 of 20 comparisons. Three of these injury events were caused by soil plus foliar applications, which were always more injurious than foliar only applications, which were more injurious than soil-only applications. Both application placement and RH significantly influenced smooth crabgrass responses to mesotrione. Smooth crabgrass phytotoxicity was lowest when mesotrione was applied only to foliage and highest when mesotrione was applied to soil and foliage. Increasing RH from 50 to 90% caused a 4- to 18-fold increase in plant phytotoxicity when mesotrione was applied only to foliage. By dissecting the plant canopy, it was noted at 14 d after treatment, when averaged over RH, that white leaves comprise 16% of leaves when only foliage was treated and 55 and 62% when applied to soil plus foliage and soil only, respectively. Furthermore, white tissue was found predominately in the two youngest leaves when mesotrione was applied to soil or both soil and foliage, but in older leaves when applied only to foliage. Data indicate mesotrione entering plants through soil travels quickly to growing points and has an equal or greater effect on plant phytotoxicity than foliar-absorbed mesotrione. In addition, foliar-absorbed mesotrione appears to increase in plants significantly with increasing RH, but does not move rapidly to growing points.

Studies were conducted to compare physiological characteristics of linuron-susceptible and -resistant Portulaca oleracea. The susceptible biotype had heavier seed and germinated more rapidly than the resistant biotype. Eight weeks after seeding, fresh and dry weights of susceptible P. oleracea plants were significantly greater than those of resistant plants. Susceptible P. oleracea had a significantly higher CO2 assimilation rate at 30 C, but was similar to that of resistant P. oleracea at 40 C. The susceptible biotype had a significantly higher CO2 assimilation rate at CO2 concentrations ≥ 600 ppm and at incident light levels ≥ 900 µmol m−2 s−1. The susceptible biotype had higher carboxylation and photochemical efficiencies.

The study aimed to unravel the interaction between ocean acidification and solar ultraviolet radiation (UVR) in Chaetoceros curvisetus. Chaetoceros curvisetus cells were acclimated to high CO2 (HC, 1000 ppmv) and low CO2 concentration (control, LC, 380 ppmv) for 14 days. Cell density, specific growth rate and chlorophyll were measured. The acclimated cells were then exposed to PAB (photosynthetically active radiation (PAR) + UV-A + UV-B), PA (PAR + UV-A) or P (PAR) for 60 min. Photochemical efficiency (ΦPSII), relative electron transport rate (rETR) and the recovery of ΦPSII were determined. HC induced higher cell density and specific growth rate compared with LC. However, no difference was found in chlorophyll between HC and LC. Moreover, ΦPSII and rETRs were higher under HC than LC in response to solar UVR. P exposure led to faster recovery of ΦPSII, both under HC and LC, than PA and PAB exposure. It appeared that harmful effects of UVR on C. curvisetus could be counteracted by ocean acidification simulated by high CO2 when the effect of climate change is not beyond the tolerance of cells.