Effect of thidiazuron and gibberellic acid on leaf yellowing of cut stock flowers

Plant hormones such as cytokinins and gibberellins are able to inhibit leaf yellowing in different species of cut flowers and potted plants. These hormones can be used alone or in combination among them for preserving chlorophyll in floriculture items. In the present study thidiazuron was tested alone or combined with GA₃ for delaying leaf yellowing of cut stock flowers during vase life. Cut flowers were placed in a controlled environment and treated for 24 hours with the following solutions: distilled water (control) or solutions containing 5, 10 μM thidiazuron (TDZ), 0.5 mM gibberellic acid (GA₃), or a combination of 0.5 mM GA₃ with 5 μM TDZ. The effect of treatments was evaluated by measuring chlorophyll content, ethylene production, leaf gas exchanges and chlorophyll a fluorescence. Results showed that TDZ was able to delay leaf yellowing in light during whole experimental period (30 days). The effect of TDZ on dark stored flowers was less effective, and also delayed chlorophyll losses for 10–12 days. TDZ and GA₃ combination did not show any synergistic nor beneficial effect. Gas exchange values such as net photosynthesis, vapour pressure deficit, stomatal conductance and water use efficiency were higher in the TDZ only treatment.     

A comparison of mutagenic effectiveness and efficiency of NMU and MNG in Sorghum

Summary A comparative study of the effectiveness and efficiency of NMU and MNG in relation to the effects in M1 plants and induction of mutations in M2 was made in a cultivated variety ofSorghum. There was a decrease in the values obtained in each of the biological criteria in the M1, namely germination, survival, seedling growth and seed fertility, with an increase in the concentration of NMU and MNG. Of the characters, survival following MNG treatments and seed fertility following NMU treatments showed the maximum reduction. NMU was not only effective in decreasing the mean of various characters in the M1, but also efficient in inducing a high frequency and wide spectrum of chlorophyll mutations in the M2 compared with MNG. Low concentrations were found to be more efficient than higher concentrations of NMU. The treated M2 population showed not only a decrease but also an increase in the mean height of plant and length of ear compared with the untreated control population. NMU caused a greater decrease in the mean of both characters and induced greater variability in the length of ear than did MNG treatment.     

Mutagenic activity of antibiotics alone and in conjunction with alkanesulfonates

Differential and combined effects of 0.25 and 0.50% antibiotics (ampicillin, neomycin, furadentine) and alkylating agents (ethyl methanesulfonate, methyl ethanesulfonate, methyl methanesulfonate) were assayed on Phaseolus vulgaris L. (2 n = 22) at the M₂ generation for chlorophyll mutations. The general types scored were Albino, Xantha, Virescens and Maculata. Yellowish-green leaves having red mid-veins and veinlets were observed only amongst the progeny raised after treatment with 0.25% ethyl methanesulfonate or 0.25% methyl ethanesulfonate + 0.25% ampicillin. The frequency of chlorophyll mutation after combined treatments in general was higher than after differential treatments. Methyl methanesulfonate among alkanesulfonates and neomycin among antibiotics induced higher frequencies of chlorophyll mutations. No chlorophyll mutant was produced by ampicillin.Although antibiotics induced a lower frequency of chlorophyll mutation than alkylating agents, the frequency and pattern of spectra of chlorophyll mutants showed an action of antibiotics in inducing mutation similar to that of alkylating agents. Therefore, it is considered that antibiotics are potential mutagens.     

Mutagenicity of radiations and chemical mutagens in Sorghum

Summary A comparative study on the relative mutagenicity of radiations (X-and gamma rays) and chemical mutagens (EMS, MMS, dES and NEU) in inducing chlorophyll, viable and total mutations was made on three cultivated varieties (Co. 11, Co. 12 and Co. 18) of Eu-Sorghum. A critical comparison of the chlorophyll, viable and total mutations shows that the mutation rate increased with an increase in dose up to a certain dose level beyond which the saturation effect was observed. EMS was found to be the most potent mutagen in inducing chlorophyll, viable and total mutations. The treatments with NEU (viable mutations) and dES (viable and total mutations) also proved to be effective. In a large number of cases the relationship between chlorophyll and total mutations was more close than that of viable to total mutation rates.This work forms part of the thesis submitted for Ph. D. degree of Univ. of Madras.     

The influence of post-treatment storage on the frequency of ethyleneimine-induced chromosomal aberrations and gene mutations in barley

Summary Dry seeds of spring barley variety MOS-121 were treated with ethyleneimine and after the treatment were stored in the desiccator over granulated KOH from 6 to 46 days. During this period statistically significant changes in the general level of chromosome rearrangements, number of chlorophyll mutations, death-rate and fertility of M 1-plants were observed. The spectrum of chlorophyll mutations also changed. The maximum genetic effect resulting from storage was noted by the 18th day, and this was followed by the decrease of injuries reached zero by the 46th day.The mode of changes in dynamics of the formation of chromosome aberrations, chlorophyll mutations and recessive lethal mutations proves the similar nature of the initial mechanisms of their potential changes.     

Mutagenicity of nitrofuran derivatives, including furylfuramide, a food preservative.

The effects of sodium azide (NaN₃) in combination with diethyl sulfate (dES) or N-methyl-N′-nitrosourea (MNH) on mutation frequency in barley were studied. It was found that sodium azide produced high frequencies of chlorophyll mutations when used alone and has a synergistic effect on mutation yields following MNH treatments. However, the mutation frequency was decreased whe azide was applied following dES treatment of seeds. The mutagenic efficiency of azide was found to be high, possibly because of low “physiological” damage. The synergistic increase in mutation yields by MNH and azide treatment indicates that azide has unusual promise as a mutagen for both practical and research applications.     

不同盐胁迫下小麦叶片渗透性调节和叶绿素荧光特性

盐胁迫对植物伤害机理受到普遍关注。本试验以‘西旱3号’小麦幼苗为材料,通过比较钠盐(150 mmol·L^-1)、钙盐(5、30 mmol·L^-1)单独及其复合胁迫对叶片渗透调节和光合特性的影响,揭示不同盐胁迫对小麦的伤害机理。结果表明: 钠盐或钙盐单独胁迫显著抑制了小麦幼苗根、茎的生长,使叶片可溶性糖和脯氨酸含量、调节性能量耗散电子产量、非光化学猝灭及玉米黄质相对含量均显著增加,而叶绿素a和叶绿素b含量、最大光化学效率、PSⅡ实际光化学效率、光化学猝灭及光合电子传递效率均显著下降。此外,钙盐对小麦幼苗生长的抑制作用更强,钠盐处理下叶片叶绿素含量减少和叶绿素荧光参数降低更显著。除了可溶性蛋白、叶黄素和玉米黄质相对含量以外,低浓度钙盐有效缓解了钠盐诱导其他各指标的变化,而高浓度钙盐进一步增大了钠盐处理小麦幼苗各参数的变化幅度。总之,钠盐和钙盐显著抑制了小麦幼苗的生长,低浓度钙盐能有效缓解钠盐对小麦幼苗的伤害,而高浓度钙盐加剧了钠盐的毒害作用。这均与叶片光合色素含量、光能捕获及光合电子传递的改变有关。此外,渗透调节物质在增强钠盐或钙盐环境中小麦幼苗的抗性方面发挥着重要作用。     

The effect of kinetin and auxin on the chloroplast structure and chlorophyll content in wheat coleoptiles

Kinetin and auxin when applied to excised segments of wheat coleoptiles bring about changes in chloroplast structure and chlorophyll content of parenchymatous cells. Auxin (IAA) alone at a concentration of 10^-5M stimulated the elongation (growth), but the chloroplast membrane system was less developed and the chlorophyll content was lowest in comparison with control and other variants. Kinetin (KIN) exhibited various effects depending on the concentration used. 10^-6M KIN somehow stimulated the elongation and enhanced the amount of grana coming to one chloroplast section, but the individual grana were relatively small and the chlorophyll content a little higher than in the control. On the other hand 10^-5M KIN which did not promote the elongation of wheat coleoptiles, had the maximum stimulatory effect on the chloroplast membrane system, especially on the occurrence of large grana, and the chlorophyll content was highest in comparison with the other variants. The occurrence of starch grains in chloroplasts was lower than in the other variants. The effect of a joint treatment of KIN and IAA did not exceed that of KIN (10^-5M) alone. Thus the development of chloroplasts and the accumulation of chlorophyll in wheat coleoptiles are stimulated by the concentration of KIN which does not promote the elongation of coleoptiles.     

Influence of chlorocholinechloride and ethrel on chlorophyll content and the “epinastic response” of the primary leaf of wheat seedlings

Wheat seedlings were cultivated in nutrient solutions containing 10^-3 M CCC, 10^-3 M CEPA or 5 × 10^-4 M CCO and CEPA, respectively. CCC applied alone or mixed with CEPA increased chlorophyll content per unit fresh matter but had no influence on the epinastio response of the primary leaf. In contrast, CEPA had no influence on chlorophyll content but greatly increased the epinastic response. The different response to the application of these substances with regard to chlorophyll content ha been claimed in a previous paper to be due to their different effect on cell extension and cell division. The epinastic response of the primary leaf suggests that ethylene participates in the reaction chain of CEPA effect on plant tissues.     

Changes occurring during aging and senescence in a submerged aquatic angiosperm (Potamogeton pectinatus)

Changes occurring during aging and senescence of leaves of a submerged aquatic angiosperm ( Potamogeton pectinatus L.) were studied. Total chlorophyll and chlorophylls a and b were maximal in mature, and minimal in old leaves. The chlorophyll a to b ratio was highest in mature leaves. During senescence, the chlorophyll content and the ratio of chlorophyll a to b decreased. The content of DNA, RNA, protein and dry weight, and the activity of alkaline pyrophosphatase decreased while free amino acids, the activity of protease, RNase and acid pyrophosphatase, and the ratio of acid to alkaline pyrophosphatase activity increased during aging and senescence. Kinetin (0.23 m M ) deferred leaf senescence by delaying the loss of chlorophyll, protein, nucleic acids and dry weight, and reducing the rise in free amino acids, the activity of protease, RNase and acid pyrophosphatase and the ratio of acid to alkaline pyrophosphatase activity; while both 0.69 m M ethrel and 0.075 m M ABA hastened senescence. Kinetin pretreatment for an optimum period (12 h) followed by ethrel or ABA treatment partially erased the senescence-promoting effect of the latter. But treatments in a reverse order markedly reduced the delaying effect of kinetin on senescence.     

Effectiveness of different mutagens in single and combined treatments

An experiment was made on the effectiveness of combined treatments with some chemical (EMS, HA, 5BDUR) and physical (UV, gamma rays) mutagens in inducing visible mutations in hexaploid wheat (Triticum aestivum) variety N.P. 870. Irradiation with gamma rays and chemical treatment with EMS produced a high frequency as well as a wide spectrum of mutations. Treatments with UV, HA and 5BDUR gave a very low frequency of mutations. Combined treatments with any of the latter three mutagens reduced the mutation frequency of gamma rays alone and of EMS alone. The probable reasons for the reduction of the mutation frequency in combined treatments are discussed.     

Interactive effects of cadmium and aluminum on growth and antioxidative enzymes in soybean

The effects of Al, Cd and pH on growth, photosynthesis, malondialdehyde (MDA) content, and some antioxidant enzyme activities of the two soybean cultivars with different Al tolerance were determined using a hydroponic culture. There were six treatments as follows: pH 6.5; pH 4.0; pH 6.5 + 1.0 μM Cd; pH 4.0 + 1.0 μM Cd; pH 4.0 + 150 μM Al; pH 4.0 + 1.0 μM Cd + 150 μM Al. The results showed that the low pH (4.0) and Al treatments caused marked reduction in the growth (root and shoot length and dry mass), chlorophyll content (SPAD value) and net photosynthetic rate. Higher malondialdehyde content, superoxide dismutase (SOD) and peroxidase (POD) activities were detected in the plants exposed to both Al and Cd than in those exposed to Al treatment alone. An expressive enhancement of SOD and POD was observed in the plants exposed to 150 μM Al in the comparison with the control plants, especially in Al-sensitive cv. Zhechun 2 which had also significantly higher Al and Cd content than Al tolerant cv. Liao-1. Cd addition increased Al content in the plants exposed to Al + Cd stress, and cv. Zhechun 2 had relatively lower Al content. The present research indicated that Al and Cd are synergistic in their effects on plant growth and some physiological traits.     

Studies on interaction of Meloidogyne incognita (Kofoid and White) Chitwood and Fusarium solani (Mart.) Sacc forming a disease complex in lentil (Lens culinaris Medik.)

Abstract

An experiment was conducted to study the effects of interaction between Meloidogyne incognita and Fusarium solani on plant length, fresh and dry weights, number of pods, chlorophyll, carotenoid, nitrogen and phosphorus contents and nitrate reductase activity in lentil plants. The results reveal a maximum damage occurring in all the plant growth, biochemical and nutrient parameters, in plants inoculated with M. incognita 10 days prior to F. solani (Mi?→?Fs). This was followed by simultaneous (Mi?+?Fs) inoculations, fungus inoculation 10 days prior to nematode (Fs?→?Mi), M. incognita alone and F. solani alone treatments. Nematode reproduction factor and root galling were highest in individual inoculation of M. incognita, while root rotting percentage was highest when nematode was inoculated 10 days prior to fungus followed by simultaneous inoculation with both nematode and fungus.     

Effects of sodium acetate and sodium chloride on EMS-induced chlorophyll mutations in barley

Sodium acetate solutions to which sodium chloride was added, and acetate or chloride alone have been used as pre-, simultaneous, and post-treatment of dry and pre-soaked seeds of barley to study their effect on the types and frequencies of ethyl methanesulphonate (EMS)-induced chlorophyll mutations in spring barley, variety Elsa, and winter barley, varieties $\text{436}\text{35}$ and Ager. Application of acetate/chloride on dry seeds before or simultaneously with EMS both resulted in the frequency of chimeral plants with chlorophyll-deficient sectors in M₁ and chlorophyll mutants in M₂ approximately being halved as compared with the controls (EMS treatment alone).An opposite effect was observed after simultaneous treatment with acetate/ chloride and EMS (pH 4.5 and pH 7.0) and application of acetate/chloride after EMS treatment of pre-soaked seeds. In this case the mutagen sensitivity, i.e. the frequency of chimeral plants with induced chlorophyll-deficient sectors in M₁ and of chlorophyll mutants in M₂, was approximately doubled as compared with the control.Separate application of both acetate or chloride as a simultaneous treatment with EMS resulted also in an increase in the chlorophyll mutation frequency as compared with EMS treatment alone.Based on these results some aspects of the acetate/chloride effect are briefly discussed.     

Frequency and spectrum of chlorophyll-deficient mutations in rice after treatment with radiation and alkylating agents

Three varieties of rice were treated with gamma rays and two alkylating agents EMS and DES, alone and in combinations, with a view to finding out the frequency and spectrum of chlorophyll mutations in relation to the genotype and the nature of the mutagen.Chlorophyll mutation frequency was enhanced with increasing dose but dropped at very high doses (doses that induced over 90% seedling lethality in M₁). The fall was attributed to either the increased mutated sector and diplontic selection after exposure to very high doses or relatively high resistance of some of the seeds.Among chlorophyll mutants in M₂ induced by radiations as well as alkylating agents, the albina type formed the majority class. EMS induced a significantly higher proportion of albinas than did gamma rays.     

Synergistic interaction between two cockroach sodium channel mutations and a tobacco budworm sodium channel mutation in reducing channel sensitivity to a pyrethroid insecticide

Pyrethroid insecticide resistance due to reduced nerve sensitivity, known as knockdown resistance (kdr or kdr-type), is linked to multiple point mutations in the para-homologous sodium channel genes. Previously we demonstrated that two mutations (E434K and C764R) in the German cockroach sodium channel greatly enhanced the ability of the L993F mutation (a known kdr -type mutation) to reduce sodium channel sensitivity to deltamethrin, a pyrethroid insecticide. Neither E434K nor C764R alone, however, altered sodium channel sensitivity. To examine whether E434K and C764R also enhance the effect of pyrethroid resistance-associated sodium channel mutations identified in other insects, we introduced a V to M mutation (V409M) into the cockroach sodium channel protein at the position that corresponds to the V421M mutation in the Heliothis virescens sodium channel protein. We found that the V409M mutation alone modified the gating properties of the sodium channel and reduced channel sensitivity to deltamethrin by 10-fold. Combining the V409M mutation with either the E434K or C764K alone did not reduce the V409M channel sensitivity to deltamethrin further. However, the triple mutation combination (V409M, E434K and C764R) dramatically reduced channel sensitivity by 100-fold compared with the wild-type channel. These results suggest that the E434K and C764R mutations are important modifiers of sodium channel sensitivity to pyrethroid insecticides.     

Effect of food and sediment pre-treatment in experiments with a deposit-feeding amphipod, Monoporeia affinis

We experimentally investigated the effects of different pre-treatments of the sediment, and the effect of daily addition of fresh phytoplankton, on the growth and survival of 1-year-old (1+) individuals of the deposit feeder Monoporeia affinis (Amphipoda). We used three different types of sieved sediment: pre-frozen muddy clay, non-pre-frozen muddy clay, and fine sand. The muddy clay contained phytoplankton originating from the surface sediment sampled in the field during the late spring bloom. No phytoplankton was initially present in sand. The experiment lasted for 18 days. M. affinis responded to the daily phytoplankton addition by increasing growth. Phytoplankton addition had no significant effects on the survival of M. affinis. Upon phytoplankton addition, the sandy and non-frozen muddy clay gave similar growth and survival responses. In contrast, the pre-frozen sediment resulted in significantly lower growth and survival. The growth was negative in all treatments without phytoplankton. Thus, the high initial chlorophyll content in the muddy clay was not of sufficient quality or concentration to allow a positive growth response in M. affinis. The growth of M. affinis was significantly correlated with the reduction of the chlorophyll. Our results indicated that M. affinis is capable of assimilating settled phytoplankton with no, or only a few days' time delay.     

Whole plant aspects of heavy metal induced changes in CO2, uptake and water relations of spruce (Picea abies) seedlings

Spruce seedlings [ Picea abies (L.) Karst.] were exposed to a range of concentrations of Zn, Cd, Hg and methyl-Hg for 5 weeks. The chlorophyll and water content of the needles were then estimated. The rates of photosynthesis, transpiration and dark respiration of the intact plant were determined using a Li-cor portable photosynthesis measuring system. Chlorophyll and water contents of needles decreased in response to all metal treatments, as did CO₂ uptake. At 1 μ M Cd, 0.1 μ M Hg and 30 and 60 μ M Zn, the decrease in CO₂ uptake could be accounted for by decreased chlorophyll concentrations. Decreased transpiration was only found at 5 μ M Cd and 0.01 μ M methyl-Hg. At 5 μ M Cd most of the decrease in CO₂ uptake could be explained by decreased chlorophyll levels and stomatal closure induced by water stress. At 0.01 μ M methyl-Hg, besides a decrease in chlorophyll concentration and partial stomatal closure, photosynthetic reactions may have been directly affected. Respiration rates were not influenced by exposure to heavy metals.     

Towards an understanding of the nature and fitness of induced mutations in germ cells of mice: homozygous viability and heterozygous fitness effects of induced specific-locus, dominant cataract and enzyme-activity mutations

A total of 219 specific-locus, 35 dominant cataract and 44 enzyme-activity mutations induced in spermatogonia of mice by radiation or ethylnitrosourea (ENU) treatment were characterized for homozygous viability as well as fitness effects on heterozygous carriers. For all 3 genetic endpoints, the frequency of homozygous lethal mutations was higher in the group of radiation-induced mutations than in the ENU-treatment group. These observations are consistent with the hypothesis that radiation-induced mutations recovered in the mouse are mainly due to small deletions while ENU induces mainly intragenic mutations. The overall fitness of mutant heterozygotes was reduced for the group of radiation-induced specific-locus, dominant cataract and enzyme-activity mutations while the ENU-induced mutations exhibited no reduction in fitness. The fitness reduction of heterozygous carriers for a newly occurring mutation in a population is important in determining the persistence of the mutation in a population, and thus the total number of individuals affected before a mutation is eventually eliminated from the population. For the present results a maximal persistence of 12 generations and a minimal persistence of 3 generations is estimated. These results are consistent with the 6-7-generation persistence time assumed by UNSCEAR (1982) in an estimate of the overall effects of radiation-induced mutations in man.     

N^＋注入对紫薇光合特性和叶绿素含量的影响

采用离子注入诱变育种技术对紫薇种子进行处理,正常播种后测两年生植株叶片的光合特性和叶绿素含量,结果表明：与对照相比,经离子注入处理后,各处理的净光合速率都有不同程度的增加,光合速率饱和时所需要的光合有效辐射均较未注入处理的低。叶绿素a和b的绝对含量呈现双峰型变化趋势,但叶绿素a的增加量受注入剂量的影响较大,叶绿素a/b比值变化不明显,离子注入处理能提高紫薇幼苗的潜在光合能力和耐荫性。