Search results for " leaves"
showing 10 items of 251 documents
Carbon autonomy of peach shoots determined by 13C-photoassimilate transport
2009
We used (13)CO(2) tracing and source-sink manipulation to determine if fruiting shoots of peach (Prunus persica (L.) Batsch) trees are autonomous or if they import carbon from neighboring shoots, and if the degree of shoot autonomy is influenced by the source-sink relationship of the shoot. In three experiments, leaf to fruit ratio (L:F) of selected fruiting shoots was moderately (2005 and 2006) or strongly (complete sink removal, 2006) altered to either enhance or inhibit movement of carbon from (13)C-labeled fruiting shoots (LFS) to adjacent non-labeled shoots (NLFS), both located within 10 cm on the same main scaffold of V-shaped peach trees. At Stages I and III of fruit growth, fruit an…
CPMAS 13C NMR Characterization of Leaves and Litters from the Reafforestated Area of Mustigarufi in Sicily (Italy)
2010
Reafforestation is generally based on the planting of exotic fast growing tree species suitable for adapting to even harsh environments. Once the introduced plants ameliorate soil conditions, they can be progressively replaced by au- tochthonous plant species. Reafforestation is applied worldwide. However, only few studies on the effect of reafforesta- tion on lands from Mediterranean regions are available. This paper reports the characterization by cross polarization 13C NMR spectroscopy of fresh leaves and superficial litters from a reafforestated area in central Sicily (Italy). NMR assign- ment is attempted. A differentiation among the molecular systems within leaves and litters is also …
Chlorophyll b is involved in long-wavelength spectral properties of light-harvesting complexes LHC I and LHC II.
2001
AbstractChlorophyll (Chl) molecules attached to plant light-harvesting complexes (LHC) differ in their spectral behavior. While most Chl a and Chl b molecules give rise to absorption bands between 645 nm and 670 nm, some special Chls absorb at wavelengths longer than 700 nm. Among the Chl a/b-antennae of higher plants these are found exclusively in LHC I. In order to assign this special spectral property to one chlorophyll species we reconstituted LHC of both photosystem I (Lhca4) and photosystem II (Lhcb1) with carotenoids and only Chl a or Chl b and analyzed the effect on pigment binding, absorption and fluorescence properties. In both LHCs the Chl-binding sites of the omitted Chl species…
Plant chlorophyll fluorescence: active and passive measurements at canopy and leaf scales with different nitrogen treatments
2015
Highlight We studied for the first time the temporal and spatial limits within which active and passive chlorophyll fluorescence measurements are comparable.
A field study on solar-induced chlorophyll fluorescence and pigment parameters along a vertical canopy gradient of four tree species in an urban envi…
2013
Abstract: To better understand the potential uses of vegetation indices based on the sun-induced upward and downward chlorophyll fluorescence at leaf and at canopy scales, a field study was carried out in the city of Valencia (Spain). Fluorescence yield (FY) indices were derived for trees at different traffic intensity locations and at three canopy heights. This allowed investigating within-tree and between-tree variations of FY indices for four tree species. Several FY indices showed a significant (p < 0.05) and important effect of tree location for the species Morus alba (white mulberry) and Phoenix canariensis (Canary Island date palm). The upward FY parameters of M. alba, and the upward…
A new tool for direct non-invasive evaluation of chlorophyll a content from diffuse reflectance measurements
2017
Abstract Chlorophyll is a key biochemical component that is responsible for photosynthesis and is an indicator of plant health. The effect of stressors can be determined by measuring the amount of chlorophyll a , which is the most abundant chlorophyll, in vegetation in general. Nowadays, invasive methods and vegetation indices are used for establishing chlorophyll amount or an approximation to this value, respectively. This paper demonstrates that H-point curve isolation method (HPCIM) is useful for isolating the signal of chlorophyll a from non-invasive diffuse reflectance measurements of leaves. Spinach plants have been chosen as an example. For applying the HPCIM only the registers of bo…
Linking chlorophyll a fluorescence to photosynthesis for remote sensing applications: mechanisms and challenges
2014
Chlorophyll a fluorescence (ChlF) has been used for decades to study the organization, functioning, and physiology of photosynthesis at the leaf and subcellular levels. ChlF is now measurable from remote sensing platforms. This provides a new optical means to track photosynthesis and gross primary productivity of terrestrial ecosystems. Importantly, the spatiotemporal and methodological context of the new applications is dramatically different compared with most of the available ChlF literature, which raises a number of important considerations. Although we have a good mechanistic understanding of the processes that control the ChlF signal over the short term, the seasonal link between ChlF…
Pigment binding of photosystem I light-harvesting proteins.
2002
Light-harvesting complexes (LHC) of higher plants are composed of at least 10 different proteins. Despite their pronounced amino acid sequence homology, the LHC of photosystem II show differences in pigment binding that are interpreted in terms of partly different functions. By contrast, there is only scarce knowledge about the pigment composition of LHC of photosystem I, and consequently no concept of potentially different functions of the various LHCI exists. For better insight into this issue, we isolated native LHCI-730 and LHCI-680. Pigment analyses revealed that LHCI-730 binds more chlorophyll and violaxanthin than LHCI-680. For the first time all LHCI complexes are now available in t…
Evaluation of Sentinel-2 Red-Edge Bands for Empirical Estimation of Green LAI and Chlorophyll Content
2011
ESA’s upcoming satellite Sentinel-2 will provide Earth images of high spatial, spectral and temporal resolution and aims to ensure continuity for Landsat and SPOT observations. In comparison to the latter sensors, Sentinel-2 incorporates three new spectral bands in the red-edge region, which are centered at 705, 740 and 783 nm. This study addresses the importance of these new bands for the retrieval and monitoring of two important biophysical parameters: green leaf area index (LAI) and chlorophyll content (Ch). With data from several ESA field campaigns over agricultural sites (SPARC, AgriSAR, CEFLES2) we have evaluated the efficacy of two empirical methods that specifically make use of the…
Responses of citrus plants to ozone: leaf biochemistry, antioxidant mechanisms and lipid peroxidation.
2006
The effects of ozone upon 3-year-old trees of Clementina mandarin (Citrus clementina Hort. ex Tan.) cv. Marisol exposed for 12 months to ambient (10 nl l(-1)) and high (30 and 65 nl l(-1)) concentrations in open top chambers (OTCs) were investigated. The data showed that in leaves, ozone reduced total chlorophylls, carotenoid and carbohydrate concentration. and increased 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production. In treated plants, the ascorbate leaf pool was decreased, while lipid peroxidation and Solute leakaGe were significantly higher than in ozone-free controls. The data indicated that ozone triggered protective mechanisms against oxidative stress in c…