Improved Mineral Acquisition, Sugars Metabolism and Redox Status after Mycorrhizal Inoculation Are the Basis for Tolerance to Vanadium Stress in C3 and C4 Grasses

Vanadium (V) can be beneficial or toxic to plant growth and the interaction between arbuscular mycorrhizal fungi (AMF) and V stress was rarely investigated at physiological and biochemical levels of plant groups (C3 and C4) and organs (roots and shoots). We tested the potential of AMF to alleviate the negative effects of V (350 mg V/Kg soil) on shoots and roots of rye and sorghum. Relative to sorghum (C4), rye (C3) showed higher levels of V and lower levels of key elements under V stress conditions. V inhibited growth, photosynthesis, and induced photorespiration (increased HDR & GO activities) and oxidative damage in both plants. AMF colonization reduced V stress by differently mitigating the oxidative stress in rye and sorghum. This mitigation was accompanied with increases in acid and alkaline phosphatase activities in plant roots and increased organic acids and polyphenols exudation into the soil, thus reduced V accumulation (29% and 58% in rye and sorghum shoot, respectively) and improved absorption of mineral nutrients including Ca, Mg and P. AMF colonization improved photosynthesis and increased the sugar accumulation and metabolism. Sugars also acted as a supplier of C skeletons for producing of antioxidants metabolite such as ascorbate. At the antioxidant level, rye was more responsive to the mitigating impact of AMF. Higher antioxidants and detoxification defence system (MTC, GST, phenolics, tocopherols and activities of CAT, SOD and POX) was recorded for rye, while sorghum (C4) improved its GR activity. The C3/C4-specificity was supported by principal component analysis. Together, this study provided both fundamental and applied insights into practical strategies to mitigate the phytotoxicity hazards of V in C3 and C4 grasses. Moreover, our results emphasize the importance of AMF as an environment-friendly factor to alleviate stress effects on plants and to improve growth and yield of unstressed plants.

The Effect of Prolonged Drought Legacies on Plant-Soil Feedbacks

Background Climate changes can shift plant-soil feedbacks (PSFs) causing unexpected knock-on effects on plant community dynamics. We test the hypothesis that prolonged drought legacies cause shifts in PSFs due to changes in plant-soil biotic interactions.Methods PSFs of twelve plant species representing four functional groups (C3 and C4 grasses, forbs, and legumes) were assessed in monocultures, and communities composed of one species from each of the four functional groups, in soils collected from plots with a five-year legacy of ambient rainfall or drought conditions under laboratory conditions. Plants were grown under well-watered conditions, with observed effects, therefore, being related to field drought legacies rather than experimental drought. Sterile soil conditioning was included to assess shifts in plant-soil biotic interactions associated with field rainfall legacies explicitly.Results C3 and C4 grasses displayed negative and positive PSFs, respectively, in both rainfall legacies treatments. PSFs of Plantago lanceolata shifted from positive to negative in drought legacies, while Cichorium intybus showed neutral PSFs in both soils. PSFs of Medicago sativa shifted from negative to positive, while Biserrula pelecinus and Trifolium repens showed neutral PSFs, in prolonged drought legacies. PSFs at the community level showed a trend to shift from near-positive to neutral PSFs in soils with a drought legacy, with significant negative PSFs observed when comparing home versus sterile soils, suggesting that drought may destabilise plant communities. Conclusion Our results provide evidence that prolonged drought legacies can modify plant community dynamics due to species-specific changes in PSFs that persist after droughts are alleviated.

Grazing management.

This chapter focuses on grazing management. Topics discussed include: (i) C3 and C4 grasses; (ii) the nutritive value of pastures; (iii) grazing systems; (iv) pasture yield, growth and quality assessment; (v) pasture utilization rate; (vi) calculation of carrying capacities and stocking rates; (vii) pasture budgeting; and (viii) feed-year plans.

LATE PLEISTOCENE SHASTA GROUND SLOTH (XENARTHRA) DUNG, DIET, AND ENVIRONMENT FROM THE SIERRA VIEJA, PRESIDIO COUNTY, TEXAS

We present new information about the Late Pleistocene Shasta ground sloth (Nothrotheriops shastensis). Spirit Eye Cave in the Sierra Vieja along the Rio Grande provides the newest evidence that the Shasta ground sloth inhabited further south in the mountains of the southwestern Trans-Pecos, Texas, than has been previously documented. The cave is one of only twelve known Nothrotheriops dung localities. During excavation of the cave, packrat middens and sloth dung were discovered. Two areas within the cave provide radiocarbon dated ground sloth dung and packrat midden macrobotanical remains which permit the reconstruction of the sloth diet and local biotic habitat at 30,800 and 12,900 calibrated YBP. The local community at 30,800 calibrated years ago was a pinyon-juniper woodland with yucca, sandpaper bush, globemallow, cactus, and barberry in the understory based on the packrat midden from the cave. The dung contents indicate that the diet of the sloth included C3 and C4 grasses along with Agave. Data for the local vegetation community and sloth diet from 12,900 years ago indicate that during this late glacial time, the region was still a pinyon-juniper woodland but also contained Celtis, Quercus, and Larrea, among other taxa.