Seasonal changes in photosystem II organisation and pigment composition in Pinus sylvestris

Conifers of the boreal zone encounter considerable combined stress of low temperature and high light during winter, when photosynthetic consumption of excitation energy is blocked. In the evergreen Pinus sylvestris L. these stresses coincided with major seasonal changes in photosystem II (PSII) organisation and pigment composition. The earliest changes occurred in September, before any freezing stress, with initial losses of chlorophyll, the D1-protein of the PSII reaction centre and of PSII light-harvesting-complex (LHC II) proteins. In October there was a transient increase in F₀, resulting from detachment of the light-harvesting antennae as reaction centres lost D1. The D1-protein content eventually decreased to 90%, reaching a minimum by December, but PSII photochemical efficiency [variable fluorescence (F_v)/maximum fluorescence (F_m)] did not reach the winter minimum until mid-February. The carotenoid composition varied seasonally with a twofold increase in lutein and the carotenoids of the xanthophyll cycle during winter, while the epoxidation state of the xanthophylls decreased from 0.9 to 0.1 from October to January. The loss of chlorophyll was complete by October and during winter much of the remaining chlorophyll was reorganised in aggregates of specific polypeptide composition, which apparently efficiently quench excitation energy through non-radiative dissipation. The timing of the autumn and winter changes indicated that xanthophyll de-epoxidation correlates with winter quenching of chlorophyll fluorescence while the drop in photochemical efficiency relates more to loss of D1-protein. In April and May recovery of the photochemistry of PSII, protein synthesis, pigment rearrangements and zeaxanthin epoxidation occurred concomitantly. Indoor recovery of photosynthesis in winter-stressed branches under favourable conditions was completed within 3 d, with rapid increases in F₀, the epoxidation state of the xanthophylls and in light-harvesting polypeptides, followed by recovery of D1-protein content and F_v/F_m, all without net increase in chlorophyll. The fall and winter reorganisation allow Pinus sylvestris to maintain a large stock of chlorophyll in a quenched, photoprotected state, allowing rapid recovery of photosynthesis in spring.Abbreviations Elips early light-induced proteins - EPS epoxidation state - F₀ instantaneous fluorescence - F_m maximum fluorescence - F_v variable fluorescence - LHC II light-harvesting complex of PSII - LiDS lithium dodecyl sulfate This research was supported by the Swedish Natural Science Research Council. We wish to thank Dr. Adrian Clarke¹ (Department of Plant Physiology, University of Umeå, Sweden) for advice on electrophoresis, valuable discussion and providing antibodies. Dr. Stefan Jansson¹ and Dr. Torill Hundal (Department for Biochemistry, University of Stockholm, Sweden) provided antibodies. Jan Karlsson¹ helped with the HPLC, Dr. Marianna Krol gave advice on green gels and Dr. Vaughan Hurry (Cooperative Research Centre for Plant Sciences, Australian National University, Canberra, Australia) provided valuable discussion.     

低温预处理过程中大麦花药内源激素的变化

很多文章曾报道低温预处理可以明显提高大麦花药反应频率。但对于低温预处理的机理,至今研究报道甚少。我们应用ＥＬＩＳＡ方法测定了大麦花药低温预处理过程中内源激素ＩＡＡ、ｉＰＡ和ＡＢＡ含量。根据实验结果,推测低温预处理改变了花药内源ＩＡＡ和ｉＰＡ含量,阻断了花粉原来的发育方向,使其由配子体的发育途径转向孢子体的发育途径。     

Effect of low-humidity treatment on growth of the lichenParmotrema tinctorum in a growth cabinet

Low-humidity treatment triggered an increase of the thallus area and the chlorophyll content in the following high-humidity condition. When low-humidity treatment for 4 days was intercalated in high-humidity conditions every 16 days, the thallus area increased 40% in 76 days.     

Resonance Raman spectra of beta-carotene in native and modified low-density lipoprotein

Low-density lipoproteins isolated between density 1.02 and 1.063 g/cm3 from normal fasting human plasma, show strong resonance Raman spectra due to the presence of beta-carotene. Three intense bands, at 1010, 1160 and 1530 cm-1, are assigned to the stretching vibrations of -C-CH3, = C-C = and -C = C- bonds, respectively, of beta-carotene. High-resolution spectra of the 1500-1600 cm-1 region reveal multiple features, suggesting the coexistence of several structural populations of beta-carotene. The modifications of lipoproteins with pH and temperature (30 degrees-42 degrees) change the resonance Raman spectra of beta-carotene. The specific binding of LDL at pH 7.0 by fibroblast cells is suppressed. Our experiments thus suggest that physical and chemical perturbations of plasma lipoproteins modify the lipid-protein interactions and thereby alter the configurational distribution of beta-carotene molecules within these particles.     

Progressive defects observed in mouse sperm during the course of three generations of selenium deficiency

Three successive generations of mice were fed a Torula yeast based Se-deficient diet with or without 0.1 ppm Se in the drinking water. The Se-deficient mice, in the course of three generations, showed a decrease in body weight, testis weight, epididymal weight, and sperm production. The percentage of morphologically abnormal sperm increased in successive generations. The majority of sperm defects were found in the midpiece region of the tail. Many of these aberrant sperm were motile. A progressive decrease in fertility was noted during the first two generations of Se deficiency. This system confirms the essential role of Se in spermatogenesis and provides a model for the evaluation of the primary effect of Se deprivation on the structural development of sperm.     

新兴垸低湖田莲藕引种栽培研究

本文报道了作者在湖北省监利县新兴垸低湖田进行的莲藕优良品种引种栽培试验结果,从低湖田试验莲藕的生长发育、产量、经济效益及生态适应性等方面说明了低湖田植藕是该区涝渍地开发利用的有效途径,同时简要提及了低湖田植藕应注意的若干技术问题。     

Etiologic factors and pathologic alterations in selenium-vitamin E deficiency and excess in animals and humans

The etiology of selenium-vitamin E (Se-E) deficiency diseases may be complex. Many of the syndromes involve combined deficiency of selenium and vitamin E. Selenium moves into the animal and human food chain from soil and plants, which may contain inadequate amounts of the nutrient in many areas of the world. Vitamin E may be in low concentration in many animal feeds unless supplements are added. Some syndromes, such as steatitis in cats, result from an increased requirement of vitamin E in diets that contain large amounts of polyunsaturated fatty acids, and these diseases will only respond to vitamin E administration. Deficiency syndromes in animals owing to pure Se deficiency are infrequent and have been produced mainly by laboratory studies utilizing extreme deficiency conditions. Other factors that may affect the occurrence of these deficiency diseases are concurrent dietary deficiency of S-containing amino acids, bioavailability of different forms of dietary Se, intake of compounds that antagonize Se (e.g., silver salts), and exposure to various prooxidant substances (e.g., iron compounds, oxygen, ozone, and various drugs). A wide variety of pathologic alterations occur in animals and humans with Se-E deficiency. Myocardial lesions are seen most frequently in calves, lambs, pigs, turkey poults, and ducklings. In humans, Keshan disease, an endemic cardiomyopathy in China, is attributed to Se deficiency. Necrosis of skeletal muscle is the most frequent lesion observed in animal species. Necrosis of smooth muscle of the gizzard and intestine may be a prominent lesion in turkey poults, ducklings, and quail. Other Se-E deficiency lesions include hepatic necrosis, gastric ulceration, intestinal and uterine lipofuscinosis, pancreatic damage, steatitis, exudative diathesis, encephalomalacia, and testicular necrosis. Selenium toxicosis is well characterized in animals and humans by neurological, hoof, and hair alterations.     

Effects of glutathione and of cysteine on intestinal absorption of selenium from selenite

The influence of glutathione (1 mmol/L) (GSH) on in vitro mucosal uptake and in vivo absorption of⁷⁵Se-labeled selenite (10 μmol/L) was investigated in rat jejunum. For comparison, the effect ofl-cysteine (1 mmol/L) on in vivo absorption of⁷⁵Se-labeled selenite was also studied. In the in vitro, uptake experiments, only the mucosal surface was exposed to the incubation medium for 3 min. For the in vivo experiments, a luminal perfusion technique was employed. GSH inhibited in vitro mucosal Se uptake, whereas absorption in vivo was stimulated by GSH.l-Cysteine also stimulated in vivo Se absorption, confirming former in vitro mucosal uptake experiments. Thus, unlikel-cysteine, GSH affected in vitro and in vivo absorption of Se from selenite differently. Enzymatic cleavage of products of the reaction of selenite with GSH occuring more efficiently under in vivo than in vitro conditions may be a prerequisite for the stimulatory effect of GSH on Se absorption. This apparently does not apply to the stimulatory effect of cysteine. Since, GSH occurs in the intestinal lumen under physiological conditions, it may contribute to the high bioavailability of Se from selenite.