In Cistus ladanifer L. the chlorophyll (Chl) concentration differed widely along a latitudinal transect in the Iberian Peninsula [1.15-3.56 g kg-i(d.m.) and 146-655 mg m*2(leaf area)], and Chl a/b ratio and A43o/A^65 showed also a considerable variation (2.79-3.38 and 1.93-3.32, respectively). Chl content on a dry matter basis increased from the top to the base of the plant, especially in individuals with high leaf area index (LAI) values. Young leaves, situated in the periphery of the plant, had lower Chl content per leaf area and higher A43o/A^65 values than mature, more sclerophyllous leaves. Plants ffom higher altitudes, that suffered cold winters, showed generally lower Chl contents than plants from warmer sites. The Chl content and A43o/A^65 index were more sensitive to intemal and environmental changes than the Chl a/b ratio.
Using intense ns-laser pulses up to 2 x 10** photons per cm^ per pulse the intensity dependence of fluorescence yield (O) of different photosystem 2 (PS2) subunits in spinách on the intensity of excitation pulse (/) was measured. A sti ong drop of O was observed with increasing laser pulse I. Measurements of the light-harvesting complex of PS2, LHC2, were taken at excitation wavelengths of 645-700 nm. A shift of the í) vs. I curves to lower I with increasing absorption cross section was observed. Measurements of PS2 and thylakoid membrane ífagments taken at a fixed excitation wavelength of 645 nm showed the same O V5, I dependences as LHC2. This suggests that LHC2-pigment proteins dominate the exciton concentration in the photosynthetic apparatus. A smáli drop of O measured at CP29 and CC2 particles was possibly caused by smaller domains. Smaller drop of O measured at D1D2 particles was similar to that of free chlorophyll (Chl), indicating that bimolecular annihilation was absent. Experimental results could be described using a simple two-level model including exciton-exciton-annihilation and depletion of Chl ground States. Good fits of measured O-intensity ciu-ves were possible for LHC2 with all the ušed excitation wavelengths. Outputs of these approximations are statements about excited statě concentration and time dependence of their decay as a function of excitation irradiance.
We consider preservation of exponential stability for the scalar nonoscillatory linear equation with several delays x˙ (t) + ∑m k=1 ak(t)x(hk(t)) = 0, ak(t) ≥ 0 under the addition of new terms and a delay perturbation. We assume that the original equation has a positive fundamental function; our method is based on Bohl-Perron type theorems. Explicit stability conditions are obtained.
For ordered (= partially ordered) sets we introduce certain cardinal characteristics of them (some of those are known). We show that these characteristics—with one exception—coincide.
A new application of the parametric anti-resonance is discussed. This phenomenon can be used not only for suppressing self-excited vibration or to reduce the externally excited vibration but also to suppressing self-excited vibration or to reduce the externally excited vibration but also to suppress the parametric resonance when certain conditions are met. Another aim is to stimulate further investigations and the practical applications. and Obsahuje seznam literatury