Effect of some substituted benzonitriles on photosynthetic activity of spinach and wheat in vivo and in vitro

The inhibitory effects of nine nitro and/or bromo-substituted benzonitrile compounds on the photosynthetic electron flow in isolated chloroplasts and on the in vivo CO₂ fixation of spinach (Spinacia oteracea L.) and wheat (Triticum aesticum L. cv. Bezoslaya) were investigated. Bromoxynil and 3-nitro-5-hromo-4-hydroxy-bcnzonitrile were the strongest and equally effective inhibitors of Ihe in vivo CO₂ fixation of spinach, hut in wheat the nitro-bromo-compound is ineffective and 3-nitro-benzonitrile is even more inhibitory than bromoxynil. None of the substances affected DCPIPH → methylviologen reduction. In the inhibition of the DCPIP reduction only the 3,5-disuhstituted 4-hydroxy-derivatives were effective. The fact that these compounds affect only the PS II reaction with both H₂O and DPC as electron donors suggests a site of inhibition on the reducing side of PS II, between Ihe PS II reaction centre and ihe DCPIP Site. It is suggested that in the inhibition of the DCPIP reduction only steric factors are important and the different electron configuration of the sterieally similar molecules may be involved only in the absorption and translocation processes of the compounds.     

Holocene eruptive activity of el chichon volcano, chiapas, Mexico

Geologic and radiometric-age data indicate that El Chichón was frequently and violently active during the Holocene, including eruptive episodes about 600, 1250, and 1700 years ago and several undated, older eruptions. These episodes, involving explosive eruptions of sulfur-rich magma and associated dome-growth processes, were apparently separated by intervals of approximately 350 to 650 years. Some of El Chichón's eruptions may correlate with unusual atmospheric phenomena around A.D. 1300 and possibly A.D. 623.     

Incorporation dynamics of dietary vegetable oil fatty acids into the triacylglycerols and phospholipids of tilapia (Oreochromis niloticus) tissues (fillet,liver, visceral fat and gonads)

Tilapia (Oreochromis niloticus) previously reared on a commercial feed were fed three experimental diets with added 60 g kg⁻¹ of soybean (SO), linseed (LO) or fish oils (FO), for 6 weeks. The final bodyweight (week 6) of fish was significantly lower when feeding the vegetable oils. At 0, 2, 4 and 6 weeks, fillet, liver, visceral fat, testis and ovary triacylglycerols (TAG) and phospholipids (PL) were analysed for their fatty acid (FA) composition. The simple FA dilution model has been successfully applied to describe the incorporation of numerous dietary FAs into both tissue TAGs and PLs. Fillet PL FAs reacted more sensitively on the FAs of the SO and LO diets, when compared to the TAGs. Alterations of the hepatic TAG and PL fractions were minor and less predictable. Testicular PLs have been found to preferentially accumulate n3 FAs, in particular docosahexaenoic acid (DHA) (C22:6 n3). In contrast, ovarian TAGs showed a predominant accretion of oleic acid by the FO diet. The increased dietary unsaturation index (SO, FO) was found to augment hepatic in vivo lipid peroxidation, as assessed by the tissue malondialdehyde concentrations.     

起苗时间对杜梨生长的影响

对定植的杜梨 (PyrusbetulaefoliaBge .)苗进行了假植苗和随栽随起苗的成活率、新梢生长量、叶片生长状况和蒸腾速率、气孔阻抗、叶温、叶温与气温差日变化的测定。结果表明 ,随栽随起苗的成活率和生长状况与各项生理指标均好于假植苗。揭示了影响树木生长的水分生理状况和过程。提出了生产中要提倡采用随栽随起苗 ,或应尽量接近随栽随起的时间。