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The physiological response of two species of grasses with C3 and C4 mechanisms syndromes, Napier grass (Pennisetum purpureum Schumach × Pennisetum glaucum (L.) R. Br) and hydric common reed grass (Phragmites australis (Cav.) Trin. Ex Steud) was examined under ambient (aCO2) and elevated CO2 (eCO2), in combination with water and temperature stress treatments. Under eCO2 and subjected to water and temperature stress, the Napier grass maintained higher daytime leaf water potential (LWP) by reducing transpiration (E) and executing larger osmotic adjustment (OA) at an average of 0.85 MPa compared with 0.42 MPa for common reed; carbon assimilation (PN) was thus higher for the Napier grass. Under aCO2 and low temperature, water stress induced no significant differences in OA between the grasses, but Napier grass still had higher PN than that of common reed. Recovery in LWP and PN following re-watering of water-stressed plants was more rapid in Napier grass than that in the common reed; the former had also higher water-use efficiency due to its low specific water use (water use/leaf area) that was just a fraction (less than 6%) that of the common reed. Exposure of common reed to eCO2 reduced stomata number, but increased it in the Napier grass, especially when subjected to water stress and high temperature. Exposure to eCO2 enhanced OA capacity and E control in Napier grass resulting in superior physiological profile over the common reed subjected to water and heat stress. [ABSTRACT FROM AUTHOR]

Ten accessions of Napier grass (Pennisetum purpureum Schumach.) were evaluated for their dry matter (DM) yield and forage quality in a semi-arid lowland (Katumani) and a relatively wet highland (Muguga) over seven growth cycles from 2011 to 2013 in tropical Kenya. Three biomass yield clusters were identified from the 10 accessions as high-yielding (HYC), medium-yielding (MYC) and low-yielding (LYC) clusters for both sites. Total biomass (shoot and root) yields (t ha−1) over the seven growth cycles were 25.3 for HYC, 22.2 for MYC and 19.6 for LYC at Katumani and 40.0, 41.4 and 29.1 at Muguga. Total biomass yield averaged over the study period was DM 22.4 t ha−1 at Katumani and 36.8 at Muguga. Rainfall productivity was higher at Katumani (28.8 kg ha−1 mm−1) than 20.8 kg ha−1 mm−1 at Muguga. Neutral detergent fibre (NDF) was lower in LYC, which was more leafy than the other clusters and there was little difference in NDF between the two sites. [ABSTRACT FROM PUBLISHER]

The article presents information on the biology of Australian weed Hyparrhenia hirta, commonly known as Coolatai grass, Tambookie grass, South African bluestem and common thatching grass. Topics discussed include its description and taxonomy, its history, current distribution and potential distribution. Also mentioned are the weed's climatic requirements, substratum, morphology and perennation and floral biology.

We examined the effects of grazing exclusion over a period of 14 years on the species richness and community composition of three plant communities with different dominant species and water regimes in the Gwydir Wetlands in eastern Australia. Responses to grazing exclusion varied among the three plant communities, and were most likely to be evident during dry periods rather than during periods of inundation. In frequently flooded plant communities, there was an increase in phytomass following exclusion of domestic livestock, but changes in plant community composition and species richness due to livestock exclusion varied depending on the morphological attributes of the dominant plant species. In a plant community where tall sedge species were dominant, livestock exclusion further increased their dominance and overall species richness declined. In contrast, where a prostrate grass species such as Paspalum distichum was dominant, species richness increased following livestock exclusion, due to an increase in the abundance of taller dicotyledon species. However, livestock exclusion in a community where flooding was less frequent and native grass species have been largely replaced with the introduced species Phyla canescens, resulted in no significant changes to phytomass, species richness or community composition among the grazing exclusion treatments over time. Our results indicate responses to exclusion of domestic livestock are dependent upon the dominant species within the plant community and will likely vary over time with the extent of wetland inundation. Grazing exclusion alone, without increased flooding, is unlikely to restore floristically degraded floodplain plant communities. [ABSTRACT FROM AUTHOR]