The xanthophyll cycle and the water-water cycle had different functional significance in chilling-sensitive sweet pepper upon exposure to chilling temperature (4 °C) under low irradiance (100 µmol m-2 s-1) for 6 h. During chilling stress, effects of non-photochemical quenching (NPQ) on photosystem 2 (PS2) in dithiothreitol (DTT) fed leaves remained distinguishable from that of the water-water cycle in diethyldithiocarbamate (DDTC) fed leaves. In DTT-fed leaves, NPQ decreased greatly accompanied by visible inhibition of the de-epoxidized ratio of the xanthophyll cycle, and maximum photochemical efficiency of PS2 (Fv/Fm) decreased markedly. Thus the xanthophyll cycle-dependent NPQ could protect PS2 through energy dissipation under chilling stress. However, NPQ had a slighter effect on photosystem 1 (PS1) in DTT-fed leaves than in DDTC-fed leaves, whereas effects of the water-water cycle on PS1 remained distinguishable from that of NPQ. Inhibiting superoxide dismutase (SOD) activity increased the accumulation of O2, the oxidation level of P700 (P700+) decreased markedly relative to the control and DTT-fed leaves. Both Fv/Fm and NPQ changed little in DDTC-fed leaves accompanied by little change of (A+Z)/(V+A+Z). This is the active oxygen species inducing PS1 photoinhibition in sweet pepper. The water-water cycle can be interrupted easily at chilling temperature. We propose that during chilling stress under low irradiance, the xanthophyll cycle-dependent NPQ has the main function to protect PS2, whereas the water-water cycle is not only the pathway to dissipate energy but also the dominant factor causing PS1 chilling-sensitivity in sweet pepper. and X.-G. Li ... [et al.].
Morphology of the nematode Viguiera dicrurusi Gupta, 1960 harboured by Dicrurus macrocercus albirictus (Hodgson) (Passseriformes: Dicruridae) from Baruipara in 24-Pargonas (South) district, West Bengal, India was studied by light and scanning electron microscopy (SEM). This represents the first study of V. dicrurusi using SEM. Scanning electron micrographs provided detailed information about the nature of pseudolabial plates, number and shape of teeth, dentate nature of striae, and the relative position of vulva, anus and phasmid opening in female. A detailed morphometrical comparison of this species with Viguiera viduae Chabaud, 1960 described from Dicrurus forficatus from Madagascar indicates that V. viduae is a junior synonym of V. dicrurusi. Two other species, Viguiera bhujangai Jehan, 1972 and Viguiera adsimilisai Sood et Kalia, 1978 are considered species inquirendae.
Let $\lbrace \beta (n)\rbrace ^{\infty }_{n=0}$ be a sequence of positive numbers and $1 \le p < \infty $. We consider the space $H^{p}(\beta )$ of all power series $f(z)=\sum ^{\infty }_{n=0}\hat{f}(n)z^{n}$ such that $\sum ^{\infty }_{n=0}|\hat{f}(n)|^{p}\beta (n)^{p} < \infty $. We investigate strict cyclicity of $H^{\infty }_{p}(\beta )$, the weakly closed algebra generated by the operator of multiplication by $z$ acting on $H^{p}(\beta )$, and determine the maximal ideal space, the dual space and the reflexivity of the algebra $H^{\infty }_{p}(\beta )$. We also give a necessary condition for a composition operator to be bounded on $H^{p}(\beta )$ when $H^{\infty }_{p}(\beta )$ is strictly cyclic.