Effects Of Norflurazon Research Articles

Effects of Norflurazon and UV Radiation on Symbiotic and Free-Living Hydra

In this study, we aimed to document the freshwater symbiotic interactions along with the impact of the abiotic environment and anthropogenic effects on the functionality of freshwater organisms. Symbiotic green hydra (Z) and free-living brown hydra (S), either separately or both species together, were treated with the herbicide norflurazon in concentrations of 2 × 10−6 mol/L (N6) and 2 × 10−7 mol/L (N7) for 72 h. Also, hydras were treated with both norflurazon and UV radiation at a wavelength of 254 nm for 2 min or were irradiated only. The next part of the experiment was performed in the same way but with added suspensions of isolated endosymbiotic alga, free-living alga, or both algae together. Mortality, migration, tentacle and tissue damage, changes in the thickness of the mesoglea of hydras, and clustering of algae were monitored. Green hydra generally showed lower rates of migration, and mortality was observed only in green hydra exposed to UV radiation. Tentacle damage was more pronounced in green hydra and included a specific fork-like structure. The use of cryofixation and TEM enabled us to partly elucidate the effect of clustering of algae. In summary, our study provides new insights into the influence of different environmental stressors and their combination on symbiotic and free-living freshwater hydras and algae and a better understanding of interactions in freshwater ecosystems.

Effects of norflurazon on СО2 fixation and Rubisco activity in some C3 and C4 plants under different light intensity

Effects of norflurazon on СО2 fixation and Rubisco activity in some C3 and C4 plants under different light intensity

Effects of Norflurazon on Green and Brown Hydra

For the first time effects of norflurazon on green (Hydra viridissima Pallas, 1766) and brown hydra (Hydra oligactis Pallas, 1766) in high- and low-light conditions were investigated in order to establish the extent of damage that this substance inflicts, with special emphasis on the "bleaching effect" and the effect on hydra-algae symbiosis. Green hydra is a typical example of an endosymbiotic organism. The gastrodermal myoepithelial cells of green hydra contain endosymbiotic algae. Norflurazon is a selective translocational herbicide that induces a "bleaching effect" on newly developed chloroplasts, resulting in a decrease of photosynthetic activity and viability of the organism. In the experiment, morphological (binocular), cytological and histological (Bouin fixative, dehydration, paraplast embedding, Hämalaun-eosine staining, light microscope) and conventional transmission electron microscopy (cTEM) (glutaraldehyde, dehydration, raisin, uranyl-acetate, Pb-citrate) were used. Depending on the concentration and light conditions, norflurazon caused mortality, deformations, changes in behavior, locomotion and asexual reproduction, changes in the structure of all 3 layers in hydras, changes in the position and shape of endosymbiotic algae inside the hydra body as well as ultrastructural changes of treated hydras and endosymbiotic algae. Under low concentrations of norflurazon the effects on hydra were similar to the controls, while in the highest concentrations especially manifested were antichloroplastal and antimitochondrial effects. Norflurazon caused a great extent of damage and induced deleterious effects also upon other cellular components such as cellular membranes, ER, Golgi apparatus, ribosomes. Newly developed buds in symbiotic green hydras were not bleached. After a recovery period, the green hydra individuals that had survived re-established regular endosymbiosis with algae and recovered completely, whereas brown hydras recovered only partially.

The effect of norflurazon on protein composition and chlorophyll organization in pigment–protein complex of Photosystem II

The pyridazinone-type herbicide norflurazon SAN 9789 inhibiting the biosynthesis of long-chain carotenoids results in significant decrease in PS II core complexes and content of light-harvesting complex (LHC) polypeptides in the 29.5-21 kDa region. The Chl a forms at 668, 676, and 690 nm that belong to LHC and antenna part of PS I disappear completely after treatment. The intensity of the Chl b form at 648 nm is sharply decreased in treated seedlings grown under 30 or 100 lx light intensity. The bands of carotenoid absorption at 421, 448 (Chl a), 452, 480, 492, 496 (beta-carotene), and 508 nm also disappear. The band shift from 740 to 720 nm and decrease in its intensity relative to the 687 nm emission peak in the low-temperature fluorescence spectrum (77 K) suggests a disturbance of energy transfer from LHC to the Chl a form at 710-712 nm.

Effect of Norflurazon on Responses of Superoxide Dismutase and Catalase in a Standard Maize Inbred Line and Superoxide Dismutase Mutant

We compared the responses of superoxide dismutase (SOD) and catalase (CAT) to a herbicide norflurazon (NF)-induced oxidative stress in leaves and mesocotyls of a standard maize (Zea mays) inbred line (W64A) to those of a SOD mutant (A130-1) having a mutation in Sod1. The changes in activities of SOD and CAT with NF treatment did not differ between W64A and A130-1. The relative transcript levels of Sod1 and Cat1 increased greatly in response to NF in leaves and mesocotyls of the two maize lines. In leaf and mesocotyl tissues, the Sod3 transcript increased only at a 33 μM NF in W64A, whereas Sod3 increased at 33 μM and 100 μM in A130-1. The Sod4A transcript increased only in mesocotyls of NF-treated A130-1, but the total Sod4A transcript level was much higher in W64A than in A130-1. Cat2 increased in the leaves of NF-treated W64A but decreased significantly in the leaves of A130-1. In mesocotyls, the Cat2 transcript increased only in A130-1 upon NF treatment. The maize variant with a mutation in Sod1 demonstrated differences in the induction of Sod and Cat transcripts from the standard inbred line W64A in response to NF-induced oxidative stress.

Multiple plastid signals regulate the expression of the pea plastocyanin gene in pea and transgenic tobacco plants.

The expression of nuclear genes encoding photosynthesis-related proteins is regulated by signals from plastids. To investigate how the pea PetE gene encoding plastocyanin is regulated by plastid signals, the effects of norflurazon, lincomycin and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), specific inhibitors of plastid-located processes generating plastid signals, have been examined. RNA-gel blot analysis of 7-day-old pea and tobacco seedlings containing the pea PetE gene showed that treatment with norflurazon and lincomycin, but not DCMU, decreased the accumulation of transcripts of pea PetE and endogenous Lhcb1 genes. Analysis of chimeric PetE gene constructs in tobacco seedlings showed that an intact PetE mRNA 5' terminus and elements within the PetE coding region were required to confer sensitivity to norflurazon and lincomycin, suggesting post-transcriptional regulation. Analysis of 4-week-old tobacco plants containing chimeric PetE constructs showed that DCMU treatment decreased the accumulation of pea PetE and Lhcb1 transcripts, but had opposite effects on the transcription of the genes in nuclear run-on assays. DCMU upregulated transcription from the pea PetE promoter whereas transcription of tobacco Lhcb1 genes was decreased. These experiments provide evidence for multiple plastid signals operating at different developmental stages and affecting transcriptional and post-transcriptional processes regulating expression of the pea PetE gene.

Plastid photodamage and Cab gene expression in barley leaves

The effects of norflurazon (NF) and amitrole (AM), two bleaching herbicides which inhibit carotenogenesis, were compared in leaves of 7‐day‐old barley (Hordeum vulgare L. cv Express) plants grown in damaging light. The herbicide effects were analysed with respect to chloroplast organization, photosynthetic functionality and nuclear photodependent expression of the Lhcb1 gene, which codes for the Lhcb1 light‐harvesting chlorophyll a/b binding protein of photosystem II. Both herbicides caused dramatic photooxidation of organelles, which were photosynthetically unfunctional. Plastids of NF‐treated plants lacked thylakoids and pigments. Plastids of AM‐treated plants had some strikingly altered membranes and contained only very small quantities of chlorophylls. Despite the presence of severely photodamaged plastids, cells of AM‐treated leaves contained high levels of Lhcb1 transcript. This transcript, on the contrary, was completely absent in the cells of NF‐treated plants. These findings suggest that in order to block expression of nuclear genes coding for plastid‐resident proteins, photodamage leading to the complete dismantling of thylakoids and to the total absence of any form of photosynthetic pigment is required.

Influence of Abscisic Acid and the Abscisic Acid Biosynthesis Inhibitor, Norflurazon, on Interactions Between Phytophthora sojae and Soybean (Glycine max)

A comparison was made of the effects of abscisic acid (ABA) and the ABA biosynthesis inhibitor, norflurazon on the interaction between soybean leaves and Phytophthora sojae. Inoculation of leaves of cv. Harosoy resulted in a compatible interaction typified by the presence of spreading, water soaked lesions with ill-defined margins while inoculation of cv. Haro 1272 resulted in an incompatible interaction with lesions restricted to the inoculation site. Activity of phenylalanine ammonia lyase (PAL) slowly increased in the compatible interaction but in the incompatible interaction there was a rapid rise in activity within 8 h after inoculation. When Haro 1272 plants were treated with ABA the normally incompatible interaction with race 1 was changed to what resembled a compatible interaction and activity of PAL was reduced to control levels. There was no visible effect on the compatible combination. In contrast when plants of cv. Harosoy were treated with norflurazon the normally compatible interaction with race 1 was changed to that which resembled an incompatible interaction and PAL activity increased to high levels rapidly. There was no effect of norflurazon on the incompatible interaction of cv. Haro 1272 with race 1. Stomata on leaves of cv. Harosoy treated with norflurazon closed within 2 h of inoculation resembling the response of stomata in normal incompatible interactions but not compatible interactions where stomata remained open. On leaves of cv. Harosoy treated with norflurazon at sites 3 and 20 mm from the inoculation point stomata also closed. These results extend and confirm the idea that ABA is a molecule that may regulate the outcome of the interaction between soybeans and P. sojae.

Effect of norflurazon on lipid metabolism in soya seedlings

Norflurazon(4-chloro,5-methylamino-2- α- α- α,trifluoro-methyl-phenyl-3-(2H)pyridazinone) (San 9789) was applied before sowing to soya seeds ( Glycine max., var. Weber). At concentrations between 10 −6 M and 10 −4 M a strong effect on the morphology and the physiology of the seedlings was observed. The seedlings became depigmented due to photobleaching of the photosynthetic pigments. A 40% reduction of the total lipid content was observed at 10 −4 M. The chloroplastic contents of MGDG, DGDG and PG decreased of 41%, 63% and 22%, respectively. In contrast, the content in extra-chloroplastic lipids (mainly PC) increased. Only a few changes in total fatty composition was observed in the treated plants with a slight increase in the percentage of C 16:0 and a concomitent decrease in the C 18:3 percentage. The fatty acid composition of MGDG and DGDG were almost totally unaffected. In PG a decrease in the percentage of C 16:1 trans (from 33.6 to 21.1%) was observed, while the percentage of C 16:0 and C 18:3 increased. In the three extra-chloroplastic classes (PC, PE and Pl) a large increase in the unsaturation level was observed resulting from an increase in the percentage of C 18:3. Studies of the lipid metabolism using radioactive labelling with [1- 14C]acetate as a precursor led to the conclusion that, in plants treated with norflurazon, the intra-chloroplastic pathway of desaturation was inhibited while a stimulation of the extra chloroplastic desaturation pathway was occuring, partly compensating the deficiency of the chloroplastic desaturases.

Response of Virginia-Type Peanut to Norflurazon

Abstract Four field experiments were conducted in North Carolina from 1994 to 1996 to determine the effect of norflurazon applied preemergence at 1.6 kg ai/ha to virginia-type peanut (Arachis hypogaea L.) cvs. NC 7, NC 9, NC 10C, NC-V 11, VA-C 92R, and AT VC-1. Injury 3 wk after planting was 7% or less in three experiments. Greater injury was noted on VA-C 92R relative to other cultivars in one of these experiments. Injury ranged from 25 to 41% in the fourth experiment, with greater injury noted on NC 9, NC-V 11, and VA-C 92R than on NC 7, NC 10C, or AT VC-1. Norflurazon did not affect peanut maturity, the percentage of extra large kernels, total sound mature kernels, or fancy pods. Norflurazon reduced peanut yield 6% irrespective of cultivars in two of four experiments.

Chloroplastic Regulation of Apoplastic α-Amylase Activity in Pea Seedlings

Photobleaching of pea (Pisum sativum L.) seedling leaves by treatment with norflurazon (San 9789) and 7 days of continuous white light caused a 76- to 85-fold increase in the activity of the primary alpha-amylase, a largely apoplastic enzyme, over normally greening seedlings. Levels of chlorophyll were near zero and levels of plastid marker enzyme activities were very low in norflurazon-treated seedlings, indicating severe photooxidative damage to plastids. As levels of norflurazon or fluence rates were lowered, decreasing photobleaching of tissues, alpha-amylase activity decreased. Levels of leaf beta-amylase and starch debranching enzyme changed very little in norflurazon-treated seedlings. Infiltration extraction of leaves of norflurazon-treated and normally greening seedlings indicated that at least 57 and 62%, respectively, of alpha-amylase activity was in the apoplast. alpha-Amylase activity recovered from the apoplast of photobleached leaves of norflurazon-treated seedlings was 18-fold higher than that for green leaves. Inhibitors of photosynthesis (DCMU and atrazine) and an inhibitor of chlorophyll accumulation that does not cause photooxidation of plastid components (tentoxin) had little effect on levels of alpha-amylase activity, indicating norflurazon-caused loss of chlorophyll and lack of photosynthesis did not cause the large induction in alpha-amylase activity. An inhibitor of both abscisic acid and gibberellin synthesis (paclobutrazol [PP333]) and an analog of norflurazon which inhibits photosynthesis but not carotenoid synthesis (San 9785) caused only moderate (about five-fold) increases in alpha-amylase activity. Lincomycin and chloramphenicol increased alpha-amylase activity in light grown seedings to the same magnitude as norflurazon, indicating that the effect of norflurazon is probably through the destruction of plastid ribosomes. It is proposed that chloroplasts produce a negative signal for the regulation of the apoplastic alpha-amylase in pea.

Abscisic Acid Content of Algae under Stress*

AbstractThe distribution of the phytohormone, abscisic acid (ABA), within the phylum of Phycophyta was investigated by an enzyme‐linked immunoassay (ELISA). Of 64 algal species tested (originating from 9 divisions, 20 classes and 36 orders, including procaryotes) all species contained ABA, whereas no ABA could be detected in the bacteria Escherichia coli, Rhodospirillum rubrum, and Halobacterium halobium. It is concluded that ABA is universally distributed within the algal kingdom and is not restricted to cormophytes. The ability to synthesize ABA must have been developed even within the procaryotes. The physiological role of ABA in some selected algae was studied by investigating 1. the distribution of ABA between the cells and the culture medium, 2. the responses of endogenous ABA to stress, 3. the synthesis of 14C‐ABA from externally applied 14C‐mevalonic acid, 4. the metabolism of ABA, 5. the effect of externally applied ABA on various physiological reactions of the algae, and the effect of norflurazon on ABA content. 14C‐mevalonic acid served as precursor of 14C‐ABA synthesis in Dunaliella cells and ABA was metabolised to the same products which have been observed in higher plants. In D. parva the internal ABA level increased upon hyperosmotic salt shocks, and in D. acidophila upon alkalization of the medium. Norflurazon caused an increase of ABA content in Dunaliella. Externally applied ABA did not affect photosynthesis, respiration and K+ content of the cells. The permeability of the plasma membrane of D. acidophila to water was slightly decreased by ABA. The possible physiological function of ABA in algae is discussed.

Effects of norflurazon, an inhibitor of carotenogenesis, on abscisic acid and xanthoxin in the caps of gravistimulated maize roots.

Maize seeds were germinated in the dark in the presence of the carotenoid synthesis inhibitor norflurazon and the levels of abscisic acid, xanthoxin and total carotenoids were measured in the root cap and in the adjacent 1.5 mm segment. In norflurazon-treated roots abscisic acid levels were markedly reduced, but an increase occurred in the levels of xanthoxin, a compound structurally and physiologically similar to abscisic acid. In the cultivar of maize (Zea mays L. cv. Merit) used for this work, brief illumination of the root is required for gravitropic curving. Following illumination both control and norflurazon-treated roots showed normal gravitropic curvature; however, the rate of curvature was delayed in norflurazon-treated roots. Our data from norflurazon-treated roots are consistent with a role for xanthoxin in maize root gravitropism. The increase in xanthoxin in the presence of an inhibitor of carotenoid synthesis suggests that xanthoxin and abscisic acid originate, at least in part, via different metabolic pathways.

Norflurazon--an inhibitor of essential fatty acid desaturation in isolated liver cells.

Norflurazon is a herbicide known to inhibit carotene biosynthesis and linolenic acid biosynthesis in plants. In the present work, the effect of norflurazon on the metabolism of studied in isolated rat liver cells and in rat liver microsomes, incubated with [1-14C] labeled linolenic acid (18:3, n-3), dihomogammalinolenic acid (20:3, n-6) and eicosapentaenoic acid (20:5, n-3). Norflurazon (0.1 mM, 1.0 mM) was found to inhibit essential fatty acid desaturation. The delta 6 desaturation is inhibited more efficiently than the delta 5 and delta 4 desaturation. The chain elongation of essential C18 fatty acids to their C20 and C22 homologs was not inhibited by norflurazon.

Effects of norflurazon (San 9789) on light‐increased extractable nitrate reductase activity in soybean [Glycine max (L.) Merr.]seedlings

Abstract. The effects of norflurazon (San 9789) on light‐increased extractable NADH nitrate reductase activity (NRA) in soybean seedlings were studied. Continuous white light (W) increased NRA steadily in root and cotyledonary tissues over a 5 d period. Morflurazon, a pyridazinone herbicide which causes chlorophyll bleaching in W, reduced the initial NRA induction rate in roots and cotyledons. However, in cotyledons of norfiurazon‐treated plants NRA increased at a more rapid rate than in the control after 24 h of W, with activity levels reaching three times those of control seedlings after 5 d. NRA induced by W in control and norflurazon‐treated cotyledons was fluence‐rate dependent. Continuous FR induced equal amounts of NRA in control and norflurazontreated tissues, suggesting that the superinduceable NRA of norflurazon‐treated plants under W is not phytochrome induced. The FR‐induced NRA of control and norflurazon‐treated cotyledons had pH optima of 6.6, but during development under W the pH optimum of control cotyledons changed from 6.3 to between 6.6 and 7.1. The pH optimum of the norflurazon‐induced NRA of the cotyledon under W was about 7.5. The NADH/NADPH NRA ratio after 4 d of W was 1.3 in control and 2.5 in norflurazontreated cotyledons. These data indicate that photosynthelic pigments are involved only secondarily in light‐induction of NRA in this system.