No abstract

Ruminants are major emitters of methane gas into the atmosphere thereby contributing to global warming. In an effort to find agents that can reduce ruminant gas emission and increase fodder digestion, plant material is being investigated. In a bioassay using ruminant faecal inoculum, the crude methanolic leaf extract of Helinus integrifolius was found to reduce gas emission at a concentration of 8.0 mg/ml. However, at this concentration fodder digestion is also reduced by 19% over a twenty four hour period and by 36% over a ninety six hour period. The sugar content of the digestate increased seven-fold and five-fold over 24 and 96 h respectively. Total phenolic content of the digestate increased 2.1 times and 1.3 times over 24 and 96 h respectively. At lower extract concentration gas emission is induced suggesting activation of microbiota. Hence, at higher concentrations gas emission is substantially decreased. The results suggest that while gas emission is reduced by addition of the extract the breakdown of cell wall material resulting in the release of sugars and phenolics is not. On the other hand, utilisation of the sugars by the ruminant flora might be substantially inhibited, since the overall digestion is reduced at this concentration of the extract.The distribution and utilisation of Sclerocarya birrea (A Rich.) Hochst., subspecies caffra (Sond) in Vhembe District, Limpopo Province, South Africa

No abstract

No abstract

No abstract

Flowering in Merxmuellera disticha was more strongly stimulated by fire in summer. Flowering tillers produced between 9 and 11 months after fire were significantly more abundant than those produced 21 to 24 months thereafter. Growth in terms of size of individuals was considered insignificant for analysis. Neighbored Hyparrhenia hirta showed, to a certain degree, an out-of-season growth, production and reproduction, whilst M. disticha and Themeda triandra on the same plots did not. The xylem water potential of H. hirta [-10.9(±0.29)], M. disticha [-14.6(±0.80)] and T. triandra [-13.8(±0.29)] on one stand differed significantly from one another (p < 0.0001), and that of H. hirta [-19.7(±0.81] and M. disticha [-34.5(±1.26)] on the other stand also differed significantly from each other (p < 0.0001). One way analysis of variance (ANOVA) thereof produced the following (F-ratio = 13.893; degrees of freedom = 29, p < 0.0001), and for H. hirta versus M. disticha, (F-ratio = 97.605; degrees of freedom = 23, p < 0.0001). Multiple range analysis tests revealed a significant difference between xylem water potentials of H. hirta from that of M. disticha and T. triandra but not between M. disticha and T. triandra.

The cycad genus, Encephalartos, is endemic to Africa with more than half of its species occurring in South Africa. Seventy-three percent of South African Encephalartos species are threatened with extinction with four species already extinct in the wild. The major threat to Encephalartos species in South Africa is the illegal trade of cycads. In addition, biotic factors, such as insect pests and microbial diseases that affect these plants, are on the increase. The aim of this study was to identify diseases and insect pests of Encephalartos species in South Africa. Symptomatic plant material and insects were collected from diseased cycad species in the KwaZulu-Natal, Limpopo and Gauteng provinces. Microbial isolates obtained were identified based on morphology and DNA sequence data. Species of Alternaria, Phoma and Pseudocercospora were often isolated from leaf spots and Bionectria and Fusarium species from dying cycads. The plant pathogen, Phytophthora cinnamomi, was isolated from dying Encephalartos tranvenosus plants in the Modjadji cycad reserve in Limpopo. Insect pests observed causing the most damage to cultivated cycads were the beetle, Amorphocerus talpa, and the scale insect, Aspidiotus capensis. A. talpa was observed infesting cycad cones in the Pretoria Botanical Gardens, causing discolouration and death of the cones. The scale insect, A. capensis, was found on the leaflets of many cycads, causing chlorosis and premature death of leaves. In this study we also report, for the first time, the scale insect, Aulacaspis yasumatsui, infesting cycads in South Africa. A. yasumatsui was identified based on morphology and DNA sequence data. Plants infested by this scale insect showed symptoms of severe leaf chlorosis and necrosis. The presence of A. yasumatsui on South African Encephalartos species is of much concern and efforts should be made to manage this pest in the country.

No abstract