Fatbardha Babani

Detection of photosynthetic activity and water stress by imaging the red chlorophyll fluorescence.

Abstract It is shown that with a new flash-lamp chlorophyll (Chl) fluorescence imaging system (FL-FIS), the photosynthetic activity of several thousand points of an intact attached leaf can be screened in a non-destructive way within a few seconds. The method allows the detection of the gradients in photosynthetic capacity over different parts of the leaf. The photosynthetic activity is sensed via imaging the Chl fluorescence at its maximum Fm and at steady state Chl fluorescence Fs of the induction kinetics and by the subsequent determination of the image of the fluorescence decrease ratio (R Fd ) which is known as the vitality index of the photosynthetic apparatus. Under water stress the photosynthetic activity decreases as seen in the images of the two fluorescence ratios R Fd and Fm/Fs. Histogram and profile analysis of Chl fluorescence images and Chl fluorescence ratios allow the quantification of the differences between normal and stressed leaves with a high statistical significance.

Measurement of differences in red chlorophyll fluorescence and photosynthetic activity between sun and shade leaves by fluorescence imaging.

With a flash-lamp chlorophyll (Chl) fluorescence imaging system (FL-FIS) the photosynthetic activity of several thousand image points of intact shade and sun leaves of beech were screened in a non-destructive way within a few seconds. The photosynthetic activity was determined via imaging the Chl fluorescence at maximum Fp and steady state fluorescence Fs of the induction kinetics (Kautsky effect) and by a subsequent determination of the images of the fluorescence decrease ratio RFd and the ratio Fp/Fs. Both fluorescence ratios are linearly correlated to the photosynthetic CO2 fixation rates. This imaging method permitted to detect the gradients in photosynthetic capacity and the patchiness of photosynthetic quantum conversion across the leaf. Sun leaves of beech showed a higher photosynthetic capacity and differential pigment ratios (Chl a/b and Chls/carotenoids) than shade leaves. Profile analysis and histogram of the Chl fluorescence yield and the Chl fluorescence ratios allow to quantify the differences in photosynthetic activity between different leaf parts and between sun and shade leaves with a high statistical significance.

Multicolour Fluorescence Imaging of Sugar Beet Leaves with Different Nitrogen Status by Flash Lamp UV-Excitation

Fluorescence images of leaves of sugar beet plants (Beta vulgaris L. cv. Patricia) grown on an experimental field with different fertilisation doses of nitrogen [0, 3, 6, 9, 12, 15 g(N) m−2] were taken, applying a new multicolour flash-lamp fluorescence imaging system (FL-FIS). Fluorescence was excited by the UV-range (280–400 nm, λmax = 340 nm) of a pulsed Xenon lamp. The images were acquired successively in the four fluorescence bands of leaves near 440, 520, 690, and 740 nm (F440, F520, F690, F740) by means of a CCD-camera. Parallel measurements were performed to characterise the physiological state of the leaves (nitrogen content, invert-sugars, chlorophylls and carotenoids as well as chlorophyll fluorescence induction kinetics and beet yield). The fluorescence images indicated a differential local patchiness across the leaf blade for the four fluorescence bands. The blue (F440) and green fluorescence (F520) were high in the leaf veins, whereas the red (F690) and far-red (F740) chlorophyll (Chl) fluorescences were more pronounced in the intercostal leaf areas. Sugar beet plants with high N supply could be distinguished from beet plants with low N supply by lower values of F440/F690 and F440/F740. Both the blue-green fluorescence and the Chl fluorescence rose at a higher N application. This increase was more pronounced for the Chl fluorescence than for the blue-green one. The results demonstrate that fluorescence ratio imaging of leaves can be applied for a non-destructive monitoring of differences in nitrogen supply. The FL-FIS is a valuable diagnostic tool for screening site-specific differences in N-availability which is required for precision farming.

Changes of Chlorophyll Fluorescence Signatures during Greening of Etiolated Barley Seedlings as Measured with the CCD-OMA Fluorometer

Summary In greening barley seedlings the chlorophyll fluorescence emmission spectra were recorded by the Karlsruhe CCD-OMA spectrofluorometer during the fast rise (fast component of Kautsky effect) and the slow decline (slow component of Kautsky effect) of the chlorophyll fluorescence kinetics. The relationships between fluorescence signatures and photosynthetic pigments were used to characterize the development of photosynthetic activity in 7d old etiolated barley seedlings during illumination with continuous white light, The shape of the chlorophyll fluorescence spectra exhibited characteristic changes during the greening of etiolated barley seedlings. At the onset of greening and a very low chlorophyll content only one fluorescence peak near 690 nm was detectable, whereas the second fluorescence peak near 735 nm, initially expressed only as a shoulder, was developed during the chlorophyll accumulation to a separate fluorescence maximum. The time course of the fluorescence intensity near 690 nm and 735 nm at maximum (fm) and steady-state of the chlorophyll fluorescence (fs) can be explained on the basis of a partial reabsorption of the emitted red chlorophyll fluorescence band F690 by the leaf chlorophyll. The chlorophyll fluorescence ratios F690/F735 at fm and fs were determined from the CCD-OMA spectra. The decreasing of the chlorophyll fluorescence ratio F690/F735 with increasing chlorophyll content during greening of the etiolated barley leaves can be expressed by a power function (curvilinear relationship): y=ax -b . The variable chlorophyll fluorescence decrease ratios (Rfd-values) as vitality index were calculated from the fluorescence intensities measured at 690 nm and 735 nm of the CCD fluorescence spectra. The Rdf690 and Rfd735 values increased during greening and exhibited the characteristics of a saturation curve. The latter was reached for Rfd690 after 24 h of illumination (chlorophyll content 14 μm -2 ) and for Rfd735 already after 6h of illumination (chlorophyll content 8 μ cm -2 ). The Karlsruhe CCD-OMA spectrofluorometer is excellently suited for photosynthetic studies as well as stress detection in plants.

Photosynthetic Activity During Autumnal Breakdown of Chlorophyll in Tree Species

The chlorophyll fluorescence analysis has been applied to describe and investigate the photosynthetic light processes and quantum conversion as well as to detect damage to the photosynthetic apparatus and its function due to the inverse relationship between photosynthetic performance and Chl emitted fluorescence (1-6). The Chl fluorescence ratio F690/F735 has been established as a non-invasive indicator of the in vivo Chl content of leaves (1, 2-5, 7). In a pre-darkened leaf the fast Chl fluorescence rise (from ground fluorescence Fo to a maximum fluorescence level Fm) and the slow fluorescence decline (from Fm to steady-state fluorescence Fs), known as Kautsky effect, reflect the functioning of the photosynthetic apparatus (4, 6). The variable Chl fluorescence decrease ratio Rfd, defined as (Fm-Fs)/Fs, measured at 690 and 735 nm is a measure of the potential photosynthetic capacity of a leaf and is correlated to the photosynthetic net CO, assimilation (4, 5, 7). The aim of this work was to determine the decline of photosynthetic activity and chlorophyll levels during the autumnal breakdown of the photosynthetic pigments via the variation of Chl fluorescence parameters.

UV-A induced fluorescence images in sun and shade leaves

Background At their natural environment plants are exposed to high fluxes of photosynthetically active and UV radiation. The increased synthesis of UV-absorbing compounds, such as flavonoids and other polyphenols, are accepted as a plant response to increased UV radiation. The increase of leaf flavonoid content can be a protection against the harmful effect of UV-B radiation as they function as antioxidant and UV filters in plants. Differences between sun and shade leaves (adapted to high light and low light respectively) of some tree species are analysed, taking in consideration differences on the UV-A absorption via fluorescence imaging of leaves.

Photosynthetic pigments of Zoster a noltii and Ruppia cirrhosa in some Albanian lagoons

In the coastal lagoons of Adriatic Sea Zostera noltii and Ruppia cirrhosa are plants with seeds and flowers, that colonizes the sandy bottom of lagoons. They are capable to produce oxygen with very weak light. Characterization of photosynthetic pigments of eelgrass Zostera noltii and Ruppia cirrhosa, were performed during the period 2002–2008 in some Adriatic lagoons: Kune‐Vaini, Patog, Karavasta and Narta. Dynamics of chlorophylls and carotenoids during the vegetation period of these plants were characterized. As a result, the chlorophyll content of Zoostera noltii taken from the Kune‐ Vain lagoon is higher than at plants collected from the other lagoons. The photosynthetic pigment content of the Zostera noltii plants is higher than of Ruppia cirrhosa. The differences on the distribution of these species in the analyzed lagoons are represented in this presentation.

Light Stress as Revealed by Chlorophyll Fluorescence in Different Ecotypes of Wheat and Triticale

The exposure of plants to high irradiance results in different responses of the photosyn-thetic apparatus, and photoinhibition is an essential one. The main site of the photo-inhibitory response seems to be located in PS2 (1, 2). All stress factors, which cause a decrease in the photosynthetizing ability (high temperature, drought, etc.), can also increase the level of photoinhibition (3). Various Chl fluorescence techniques have been applied to explain the effect of high irradiance on the photosynthetic apparatus (4-6). High light may lead to a differential damage of electron transport and to thylakoid peroxidation (4). It is not yet clear, if cultivated wheat varieties respond in the same way or differently to photoinhibition as induced by high irradiance. We have chosen Albanian and Romanian varieties of wheat and triticale to cover different types of resistance with respect to drought and heat, the most damaging environmental stresses in Albania and Romania. The main objective was to detect different sensitivity to high irradiance (2000 µmol m−1 s−1) in these cultivars using chlorophyll fluorescence techniques.