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Carnegie, CA, United States

Sharma N.,University of Texas at Austin | Sharma N.,Carnegie Institute of Science | Xin R.,University of Texas at Austin | Kim D.-H.,University of Texas at Austin | And 3 more authors.
Development (Cambridge) | Year: 2016

Flowering in plants is a dynamic and synchronized process where various cues including age, day length, temperature and endogenous hormones fine-tune the timing of flowering for reproductive success. Arabidopsis thaliana is a facultative long day (LD) plant where LD photoperiod promotes flowering. Arabidopsis still flowers under shortday (SD) conditions, albeit much later than in LD conditions. Although factors regulating the inductive LD pathway have been extensively investigated, the non-inductive SD pathway is much less understood. Here, we identified a key basic helix-loop-helix transcription factor called NFL (NO FLOWERING IN SHORT DAY) that is essential to induce flowering specifically under SD conditions in Arabidopsis. nfl mutants do not flower under SD conditions, but flower similar to the wild type under LD conditions. The no-flowering phenotype in SD is rescued either by exogenous application of gibberellin (GA) or by introducing della quadruple mutants in the nfl background, suggesting that NFL acts upstream of GA to promote flowering. NFL is expressed at the meristematic regions and NFL is localized to the nucleus. Quantitative RT-PCR assays using apical tissues showed that GA biosynthetic genes are downregulated and the GA catabolic and receptor genes are upregulated in the nfl mutant compared with the wild type, consistent with the perturbation of the endogenous GA biosynthetic and catabolic intermediates in the mutant. Taken together, these data suggest that NFL is a key transcription factor necessary for promotion of flowering under non-inductive SD conditions through the GA signaling pathway. © 2016 Published by The Company of Biologists Ltd. Source


Wessels K.J.,South African Council for Scientific and Industrial Research | Mathieu R.,South African Council for Scientific and Industrial Research | Erasmus B.F.N.,University of Witwatersrand | Asner G.P.,Carnegie Institute of Science | And 5 more authors.
34th International Symposium on Remote Sensing of Environment - The GEOSS Era: Towards Operational Environmental Monitoring | Year: 2011

People in the rural, communal areas of South Africa rely on live fuel wood for more than 90% of their energy requirements. Using airborne lidar from the Carnegie Airborne Observatory (CAO) we compared tree canopy cover and height distributions between communal landscapes with heavy utilization to fully protected public and private reserves in the Lowveld of South Africa. Rangelands and fields in most of the communal sites had more vegetation cover in the 5-7m and >7m classes than most of the conservation sites, presumably due to the absence of elephants in communal rangelands. On granite substrates there was a 50% reduction in woody cover below 5m in communal rangelands. These results in conjunction with related studies, suggest that communal land use have a higher impact on the woody cover below 5m than both elephants and fire. Source


Wessels K.J.,South African Council for Scientific and Industrial Research | Mathieu R.,South African Council for Scientific and Industrial Research | Erasmus B.F.N.,University of Witwatersrand | Asner G.P.,Carnegie Institute of Science | And 10 more authors.
Forest Ecology and Management | Year: 2011

Millions of people rely on savannas for ecosystem services, such as the provision of grazing and fuel wood, so it is important to determine the extent to which utilization affects woody vegetation resources. Using airborne LiDAR from the Carnegie Airborne Observatory (CAO), we quantified and compared tree canopy cover and height distributions between areas of contrasting management in the Lowveld savanna region of South Africa - a region connecting communal landscapes with heavy utilization (especially fuel wood harvesting) to fully protected public (Kruger National Park - KNP) and private reserves (SabiSand Game Reserve - SSGR) that conserve biodiversity. Differences in total woody vegetation cover and cover within functional height classes (1-2. m, 2-3. m, 3-5. m, 5-7. m and >7. m) were investigated between 7 sites located within (i) conservation areas (in KNP, SSGR), (ii) communal rangelands or (iii) cultivated fields in communal areas. The impact of human utilization on wood resources in the communal areas varied widely between sites. Heavy utilization on gabbro substrate greatly reduced total woody cover of the rangelands, while two other communal rangelands that were presumably less intensively utilised had double the total woody cover of conservation areas. Rangelands and fields in most of the communal sites had more vegetation cover in the 5-7. m and >7. m classes than most of the conservation sites, presumably due to the absence of elephants in communal rangelands and the active preservation of large fruiting trees. On granite substrates, which account for the majority of the study area, there was a 50% reduction in woody cover below 5. m in communal rangelands. Although large trees were clearly being conserved in communal rangelands and fields, there was a relatively low cover of vegetation below 5. m, which raise doubts about recruitment and long-term sustainability of the tree resources. These results in conjunction with other studies based on the CAO LiDAR data for experimental burn plots and large mammal exclosures in KNP, suggest that communal land use on granite substrates have a higher impact on the woody cover below 5. m than both elephants and fire. © 2010 Elsevier B.V. Source

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