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Transcriptome-Wide Gene Expression Plasticity in Stipa grandis in Response to Grazing Intensity Differences
(MDPI (Basel, Switzerland), 2021-11-02) Dang Z; Jia Y; Tian Y; Li J; Zhang Y; Huang L; Liang C; Lockhart PJ; Matthew C; Li FY; Hobza R
Organisms have evolved effective and distinct adaptive strategies to survive. Stipa grandis is a representative species for studying the grazing effect on typical steppe plants in the Inner Mongolia Plateau. Although phenotypic (morphological and physiological) variations in S. grandis in response to long-term grazing have been identified, the molecular mechanisms underlying adaptations and plastic responses remain largely unknown. Here, we performed a transcriptomic analysis to investigate changes in gene expression of S. grandis under four different grazing intensities. As a result, a total of 2357 differentially expressed genes (DEGs) were identified among the tested grazing intensities, suggesting long-term grazing resulted in gene expression plasticity that affected diverse biological processes and metabolic pathways in S. grandis. DEGs were identified in RNA-Seq and qRT-PCR analyses that indicated the modulation of the Calvin-Benson cycle and photorespiration metabolic pathways. The key gene expression profiles encoding various proteins (e.g., ribulose-1,5-bisphosphate carboxylase/oxygenase, fructose-1,6-bisphosphate aldolase, glycolate oxidase, etc.) involved in these pathways suggest that they may synergistically respond to grazing to increase the resilience and stress tolerance of S. grandis. Our findings provide scientific clues for improving grassland use and protection and identifying important questions to address in future transcriptome studies.
A study of seed production in 'Grasslands Ruanui' perennial ryegrass(Lolium Perenne L.) 'Grasslands Kahu' Timothy (Pheleum Pratense L.) prairie grass (Bromus Unioloides H.B.K.) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, New Zealand
(Massey University, 1971) Hill, Murray John
The place of grasslands in the economy of New Zealand is paramount. Consequently grassland seeds must and do play a vital role in the agricultural industry. Increasing land values and soaring costs make it imperative that our farms are sown with seed of the highest quality. On many farms seed production is only considered as secondary to the production of meat and milk. It is only in seasons when stock feed is abundant that many areas are closed for the production of seed. It would be to the advantage of the seed industry if grass seed production was viewed more as a primary consideration with stock grazing being employed to assist in the management of the seed crop rather than the present 'catch' crop system employed on many farms. This system would also help to reduce the large annual fluctuation in national seed production. Herbage seed production in this country amounts to about 18,000 tons annually although fluctuations in this figure do occur (1967 20,370 tons, 1968 17,430 tons, 1969 18,770 tons, 1970 14,880 tons). In 1970 seed exports represented a total value of over $7 million, of which approximately $0.7 million was obtained from the export of perennial ryegrass seed. In recent years a number of grassland workers have carried out studies on various aspects of seed development and production. Despite this, however, much work still remains to be done before the physiological processes underlying seed production are fully understood. Some of these workers have found it necessary to study the position and contribution of individual tillers to seed production. In comparison, studies of the factors influencing anthesis, fertilisation and seed maturation have been somewhat neglected. The production of a large number of head-producing tillers, each bearing large numbers of florets is obviously not enough. A high percentage of these florets must undergo anthesis, be effectively fertilised and ultimately develop to maximum seed weight and germination capacity if the potential yield of the crop is to be fully realised. This suggests that seed yield might be considerably increased if the conditions required at each of these stages were more fully understood. During the late summer, autumn and winter tillers grow vegetatively and it is not until the spring that those tillers destined to produce heads actually begin reproductive development. It is at this time that the first contribution to total seed yield occurs, viz. the number of reproductive tillers per unit area. Ear development continues until shortly before ear emergence at which point the number of florets per head is fixed. Subsequently, anthesis, pollination and fertilisation follow to determine the seed-set component of total yield. Finally the seeds develop and mature to determine the final yield component-seed weight.
Effects of elevated atmospheric CO2 concentrations on carbon and nitrogen fluxes in a grazed pasture : a thesis presented in partial fulfilment of the requirements for the degree of Ph. D. in Plant Science at Massey University and the degree of Docteur en Sciences, speciality Sciences Agronomiques at the Institut National Polytechnique de Lorraine
(Massey University, 2003) Allard, Vincent
Predicting the response of grazed grasslands to elevated CO2 is of central importance in global change research as grasslands represent 20% of the worlds' land area and grassland soils are a major sink for carbon (C). Grasslands responses to elevated CO2 are strongly controlled by the availability of other nutrients and nitrogen (N) in particular. There have been many previous studies of N cycling in grasslands exposed to elevated CO2 but none of these experiments were grazed. In this thesis I present data on CO2 effects on N cycling from an experimental system (FACE: Free Air Carbon dioxide Enrichment) that enabled grazing to be included. The thesis focuses on the effects of elevated CO2 on the different processes involved in organic matter (OM) returns from the plant to the soil and the consequences for N availability. In Chapter 1, it was shown that elevated CO2 modified N returns by grazing animals by altering the partitioning of N between faeces and urine creating a potential for enhanced N losses at elevated CO2. Plant litter decomposition rates were, at the ecosystem scale, not affected by elevated CO2 (Chapter 3), but a marked increase in the organic matter fluxes, from roots, led to an accumulation of coarse OM in the soil (Chapter 4). In Chapter 5, using 14C and 15N labelling, I compared short-term (plant mediated) and long-term (soil mediated) effects of elevated CO2 on soil OM dynamics and concluded that soil OM accumulation under elevated CO2 was not caused by C or N limitation but probably by the availability of other nutrients. The thesis demonstrates that the inclusion of grazing animals can strongly modify N cycling under elevated CO2. As most grasslands are grazed, the prediction of grassland responses to elevated CO2 must be derived from systems in which animals are an integral part.

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