At present, сhlorophyll meters are widely used for a quick and nondestructive estimate of the chlorophyll (Chl) content in plant leaves. Chlorophyll meters allows to estimate the Chl content in relative units -the chlorophyll index (CI). However, using such meters, one can face a problem of converting the CI into the absolute values of the pigment content and comparing the data acquired with different devices and for different plant species. Many Chl meters (SPAD-502, CL-01, CCM-200) demonstrated a high degree of correlation between the CI and the absolute pigment content, and a number of formulas have been deduced for different plant species to convert the CI into the absolute value of the photosynthetic pigment content. However, such data have not yet been acquired for the atLEAF+ chlorophyll meter. The purpose of the present research was to assess the applicability of the atLEAF+ Chl meter for estimating Chl content. A significant speciesspecific exponential relationships between the atLEAF value (corresponding to CI) and extractable Chl a, Chl b, Chl (a+b) for Calamus dioicus and Cleistanthus sp. were shown. The correlations between the atLEAF values and the content of Chl a, Chl b, and Chl (a+b) per unit of leaf area was stronger than per unit of dry leaf mass. The atLEAF value-Chl b correlation was weaker than that of atLEAF value-Chl a and atLEAF value-Chl (a+b) correlations. The influence of light conditions (Chl a/b ratio) on the atLEAF value has also been shown. The obtained results indicate that on condition of the right calibration the atLEAF+ Chl meter is a cheap and convenient tool for a quick nondestructive estimate of Chl content and can be used for this purpose along with other Chl meters.
By the bank of the Northern Dvina River for the first time Nymphoides peltata was registered in 2014. In the course of 4 years the area occupied by the popula tion increased twofold and the projective cover degree of floating leaves also rose from 50 % in 2014 to 100 % with a considerable overlap of leaf blades in 2018. Structuralfunctional adaptations (high values of SLA and leaf thickness) are aimed at the acceleration of photosynthesis and growth. The analysis of the ra pid light curves of chlorophyll fluorescence demonstrated that the species is welladapted to the medium range of light values (400-600 µmol m 2 s 1). The op ti mal values of the maximum photochemical quantum yield of PS II (Fv/Fm = 0.81) are indicative of the absence of stress conditions. Our data indicate that Nymphoides peltata is welladapted to the environment in the studied habitat, have the high capacity for extending over a new territory and demonstrates signs of an invasive species.
In the present paper, the results of the research of biometric parameters and functional peculiarities of photosynthetic apparatus of Stellaria humifusa in West Spitsbergen are discussed. The study showed that the largest proportion of the mat is composed of a brown layer of dead leaves covering the assimilative organs (about 70%). Green leaves and shoots accounted for about 20%, whereas generative organs – for about 10% of the mat mass. The values of the maximum photochemical quantum yield of PS II (FV/FM) in all the studied plants were lower than the optimal values (0.83), which suggests that the plants are exposed to stress factors. The low values of chlorophyll and carotenoid content and relatively high values of the light-harvesting complex (70-80%), the sharp decrease in the quantum yield of PS II (FPSII) entailed by a marginal increase in PPFD indicative of a sufficiently high of photochemical activity within the range of low and medium values of light. It also suggests that Stellaria humifusa is well-adapted to the shaded conditions created in the mat. Besides, a considerable decrease the maximum fluorescence yield of a light-adapted leaf (FM´) at increasing PPFD was observed, which suggests that Stellaria humifusa has a well-developed mechanism of energy dissipation via the non-photochemical (NPQ) pathway. The rapid development of NPQ gives reason to assume that, under high light conditions, non-photochemical quenching is likely to serve as the main mechanism for preventing the photodamage of the photosynthetic apparatus. Thus, it was shown that the photosynthetic apparatus of Stellaria humifusa works efficiently under the conditions created in the mat, and the thick layer of dead leaves covering the assimilative organs, on the one hand, protects them from excessive light, and on the other hand, absorbs thermal energy, which raises temperature of the local habitat.
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