Browsing by Subject "Chlorophyll fluorescence"

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  • Pavicic, M.; Wang, F.; Mouhu, K.; Himanen, K. (2019)
    Seed quality is an important factor for seedling vigour as well as adult plant resilience. The key quality attributes are related to physical characteristics, physiological performance, genetic background and health status of the seeds. Many ways to address seed quality attributes have been developed and recently many of them have featured automated high throughput methods. In our study, we addressed two of the seed quality attributes, namely physiological performance and genetic background by analysing germination rates in our mutant collection. These mutants represent ubiquitin E3 ligases that transcriptionally respond to abscisic acid (ABA). This plant hormone is an important regulator of germination and seedling establishment. To facilitate in vitro germination screens of large seed collections a high throughput image-based assay was developed. As a read out of the germination on ABA treatment the cotyledon emergence was detected with top view chlorophyll fluorescence camera. By applying the ABA treatment during germination, RING-type ubiquitin E3 ligase mutants were identified, showing either resistant or sensitive responses to ABA. In conclusion, a scalable high throughput screen for in vitro germination assay was established that allowed fast screening of tens of mutants in a hormone supplemented media.
  • Rey-Carames, Clara; Tardaguila, Javier; Sanz-Garcia, Andres; Chica-Olmo, Mario; Diago, Maria P. (2016)
    Precision viticulture requires the characterisation of the spatio-temporal variability of the vineyard status to design the appropriate management for each area. The goal of this work was to characterise the spatio-temporal variability of leaf chlorophyll (Chl) and nitrogen (N) content and their relationship with the vegetative growth in a three ha commercial vineyard (Vitis vinifera L.) using a geostatistical approach. Leaf Chl and N contents were assessed by two fluorescence indices provided by a hand-held fluorescence sensor. Fluorescence measurements were taken along five dates, from veraison to harvest, on 72 sampling points delineated on a regular grid across the vineyard. Shoot pruning weight (SPW) was measured for each sampling point as indicator of the grapevine vegetative growth. Geostatistical analysis was applied to model the spatial variability of leaf Chl and N content and SPW. The spread showed an increase of the variability of leaf Chl and N content during the ripening period, reaching maximum values prior to harvest. The variograms illustrated a similarity of the spatial variability structure of leaf Chl at all timings, unlike N which showed changing spatial variability structures along the ripening period. The Kappa index evidenced a slight intra-season stability for both Chl and N and showed that N could not be used alone as an indicator to delineate vigour management areas. The existence of spatio-temporal variability of key vegetative components was proved and its knowledge is crucial to implement precision viticulture approach such as variable rate application of fertilizers or water as needed. (C) 2016 IAgrE. Published by Elsevier Ltd. All rights reserved.
  • Zhang, Zhaoying; Zhang, Yongguang; Porcar-Castell, Albert; Joiner, Joanna; Guanter, Luis; Yang, Xi; Migliavacca, Mirco; Ju, Weimin; Sun, Zhigang; Chen, Shiping; Martini, David; Zhang, Qian; Li, Zhaohui; Cleverly, James; Wang, Hezhou; Goulas, Yves (2020)
    Quantifying global photosynthesis remains a challenge due to a lack of accurate remote sensing proxies. Solar-induced chlorophyll fluorescence (SIF) has been shown to be a good indicator of photosynthetic activity across various spatial scales. However, a global and spatially challenging estimate of terrestrial gross primary production (GPP) based on satellite SIF remains unresolved due to the confounding effects of species-specific physical and physiological traits and external factors, such as canopy structure or photosynthetic pathway (C-3 or C-4). Here we analyze an ensemble of far-red SIF data from OCO-2 satellite and ground observations at multiple sites, using the spectral invariant theory to reduce the effects of canopy structure and to retrieve a structure-corrected total canopy SIF emission (SIFtotal). We find that the relationships between observed canopy-leaving SIF and ecosystem GPP vary significantly among biomes. In contrast, the relationships between SIFtotal and GPP converge around two unique models, one for C-3 and one for C-4 plants. We show that the two single empirical models can be used to globally scale satellite SIF observations to terrestrial GPP. We obtain an independent estimate of global terrestrial GPP of 129.56 +/- 6.54 PgC/year for the 2015-2017 period, which is consistent with the state-of-the-art data- and process-oriented models. The new GPP product shows improved sensitivity to previously undetected 'hotspots' of productivity, being able to resolve the double-peak in GPP due to rotational cropping systems. We suggest that the direct scheme to estimate GPP presented here, which is based on satellite SIF, may open up new possibilities to resolve the dynamics of global terrestrial GPP across space and time.
  • Gehrmann, Friederike; Lehtimäki, Iida-Maria; Hänninen, Heikki; Saarinen, Timo (2020)
    In tundra ecosystems, snow cover protects plants from low temperatures in winter and buffers temperature fluctuations in spring. Climate change may lead to reduced snowfall and earlier snowmelt, potentially exposing plants to more frequent and more severe frosts in the future. Frost can cause cell damage and, in combination with high solar irradiance, reduce the photochemical yield of photosystem II (phi(PSII)). Little is known about the natural variation in frost exposure within individual habitats of tundra plant populations and the populations' resilience to this climatic variation. Here, we assessed how natural differences in snowmelt timing affect microclimatic variability of frost exposure in habitats of the evergreenVaccinium vitis-idaeain sub-Arctic alpine Finland and whether this variability affects the extent of cell damage and reduction in phi(PSII). Plants in early melting plots were exposed to more frequent and more severe frost events, and exhibited a more pronounced decrease in phi(PSII), during winter and spring compared to plants in late-melting plots. Snowmelt timing did not have a clear effect on the degree of cell damage as assessed by relative electrolyte leakage. Our results show that sub-Arctic alpineV. vitis-idaeais currently exposed to strong climatic variation on a small spatial scale, similar to that projected to be caused by climate change, without significant resultant damage. We conclude thatV. vitis-idaeais effective in mitigating the effects of large variations in frost exposure caused by differences in snowmelt timing. This suggests thatV. vitis-idaeawill be resilient to the ongoing climate change.