摘要:

SummaryDesign and performance of a 100‐cell seed germinator capable of simultaneously generating 100 different diurnal temperature cycles with extremes lying between 0 and 45°C is discussed. Each individual cell is equipped with a separate electronic temperature controller employing a thermistor for temperature sensing. The set temperature for each cell is determined by a precision reference resistor in the controller circuit. Six different reference resistors corresponding to six different temperatures are provided for each cell. The reference resistors are mounted on plug‐in modules with one module for each cell. Heating or cooling of the individual cells is provided by thermoelectric heat pumps. Temperature cycling, which approximates a sine function, is achieved by switching the six reference resistors, one at a time, into the controller circuits at appropriate times during a 24h period. Each cell is designed to accept a standard 100 mm Petri dish to contain the seeds. The cells have glass covers to allow entry of light essential for germination of some species.The benefit of using this type of germinator to assess the germination response ofAlyssum alyssoidesL.,Artemisia absinthiumL.,Euphorbia esulaL. andSetaria viridis(L.) Beauv., is discussed. Three dimensional germination response surfaces are given for the four spe

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1985.tb00632.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryInterspecific hybrids were obtained between two triazine‐resistant forms of the wild speciesSetaria viridisand the triazine‐susceptible cultivated foxtail millet (Setaria italica). The main agronomic characteristics of the hybrids were generally intermediate between the parental forms, except for fertility which was low. Some differences were observed according to the wild parent used. Progeny analysis confirmed the cytoplasmic inheritance of the resistance. The creation of resistant cultivars would allow the use of triazines in foxtail millet cultivat

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1985.tb00633.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryCurrently important alien weeds that have reached their final distributions are characterized by the high initial rates of spread with which they attained these distributions. Alien weeds, now seemingly unimportant but spreading at high rates, might be tomorrow's noxious weeds. It is suggested that rates of spread of species in a regional alien weed flora that have not yet reached final distributions may be used as indices for identifying future troublesome species. A literature search of several plant ecological attributes revealed that rapid seed germination, especially at low temperatures, may be associated with rapidly spreading weeds.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1985.tb00634.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryThe elongation rates of single attached leaves of rice (Oryza salivaL.) were recorded. The effect of pretilachlor on the elongation rates and the safening effect of CGA 123407 [4, 6‐dichloro‐2‐phenyl‐pyrimidine] were evaluated. Both chemicals were applied to the roots in a nutrient solution.Pretilachlor reduced leaf elongation in concentrations as low as 300 μg−1(9–6 × 10−7M) but. for combination trials with the safener, 3 mg 1−1(9–6 × 10−6M) was used. in combination with pretilachlor the safener prevented damage in very low concentrations. The ratio of pretilachlor to safener, 30:1, was sufficient when both chemicals were given to roots in nutrient solution, although for field work the ratio of 3:1 is recommended. The safener alone did not influence the elongation rate of rice leaves in the concentrations used. When pretilachlor was given to the roots and CGA 123407 to the shoot, some delay in the herbicidal action was recorded but even with high concentrations of the safener no continuous safening effect was achieved.CGA 123407 was also effective when given previous to the herbicide. This proved true even with a 2‐day interval between safener uptake and application of the herbicide. When pretilachlor was given first, the safener effected recovery to various degrees when given 1–4 days after the herbicide application.When pretilachlor was given for a limited period of time only (1–3 days) and was subsequently removed from the nutrient solution, recovery of the plant occurred. It is speculated that the safener either helps this recovery or else competitively prevents the herbicide from occupying the sites of action or from keeping them occupi

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1985.tb00635.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryThe survivalof Alopecurus myosuroidesseeds was studied in soil under arable cropping and short term grass leys in which seed return was prevented. At two winter wheat sites, where weed seeds were sown, the mean annual seed decline was 73–83% over a 2‐ or 3‐year period. The rate of decline was similar with all the cultivation systems studied: ploughing, tine cultivation and direct drilling. Seeds buried initially by ploughing, and then not disturbed by cultivation, were slightly more persistent.At five arable sites with natural populations ofA. myosuroides, seed numbers declined to an average of 3% of the original amount present after 3 years, and to 1% after 4 years. Initial populations of over 50 000 seeds m−2were recorded. Plant populations were not always proportional to the total seed content of the soil, especially on ploughed land.Seed decline in two grass fields was similar to that under arable cropping.A. myosuroidesplants were recorded in a wheat crop following a 2‐year grass ley. Weed plants did not persist in the vegetative state in grass used for conservation and grazing.At all sites, appreciable quantities of seeds were still present in the soil after 2–4 years. Although a relatively small proportion of seeds survived, the actual number of seeds surviving was substantial. For this reason, it was concluded that any eradication policy is unlikely to be effective in a cropping system dominated by win

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1985.tb00636.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryAvena fatuawas sown in a cultivation experiment in the autumn of 3 successive years. For each population seedling emergence and viable seeds in the soil were recorded for 4 years in crops of winter barley in which new seed production was prevented.About half of the seeds sown were recovered after 1 year. In subsequent years viable seeds in the soil declined more rapidly with tine cultivation than with ploughing. After 4 years up to 5% of the original seeds were still viable. One population exhibited greater seed dormancy than the other two populations, due it is thought to higher summer rainfall and the greater availability of moisture during seed maturation.Most seedlings emerged in the autumn and spring, between 12 and 18 months after sowing. A total of 950 seedlings emerged from 12 000 seeds sown; 21% of these seedlings came from new seeds (<1 year old), 57% from seeds 1–2 years old, 14% from seeds 2–3 years old and 8% from seeds 3–4 years old. Autumn seedlings arose fairly evenly from all age groups while spring seedlings mostly came from the 1–2‐year‐old seeds. With tine cultivation total seedlings over 4 years represented 9–7% and with ploughing 6–2% of the original seeds sown.A. fatuawas more persistent than in previous experiments in spring barley, which suggests that control measures would have to be applied for longer in a succession of winter cereals than spring‐sown crops to reduceA. fatuat

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1985.tb00637.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryLinear regression of dry weight of weeds against crop density, together with the use of diversity indices and principal component analysis were used to derive information about changes in the behaviour of annual weeds over the growing season and in response to a wide range of crop densities in vining peasPisum sativumL. Using linear regression it was possible to quantify reductions in weed dry weights per unit increase in crop plant density The ‘weed losse’ factor was acceptably consistent between experiments. Indices examining richness and evenness showed that numbers of weed species declined with increasing crop density and as the season progressed, but although species evenness became less at successive sampling dates the presence of a pea crop, whatever its density, did not radically alter the composition of the weed flora. Principal component analysis demonstrated that although there was competition within the weed flora, the crop did not replace the dominant weed species on high density plots, but reduced growth of all weed species al

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1985.tb00638.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryExperimental granules were made from moistened calcareous loess (pH 8·5) containing 2% w/w gum xanthan and chloramben sodium salt at w/w concentrations of 0·4–3·6%. Haloxyfopmethyl*(DOWCO‐453 ME) {Methyl 2‐(4‐((3‐chloro‐5‐(trifluoromethyl)‐2‐pyridinyl)oxy)‐phenoxy)propanoate) was dissolved in tung oil at a range of concentrations and poured on the dried chloramben granules with stirring. In the glasshouse, dry granules containing chloramben plus haloxyfop‐methyl spread pre‐emergence at the rate of 0·8 + 0·4 kg ha−1reduced the dry weight of maize(Zea maysL.), red rice (Oryza sativa L.),Abutilon theophrastiMedic., andSesbania exaltata(Raf.) Cory by 89, 100, 94, and 68%, respectively, with no injury to soybeans[Glycine max(L.) Merr.]. Coated granules spread pre‐emergence controlledA. theophrastiand volunteer maize grown from seed sown in soil up to 10 cm deep. In a preliminary field test, the experimental granules reduced numbers of weeds in soybeans and improved crop yield. Ten weeks after treatment, chloramben granules coated with haloxyfop‐methyl gave 97% control ofSorghum halepense(L.) Pers compared to 80% by uncoated granules. Linuron granules coated with haloxyfop‐methyl gave 85% control compared to 12% by uncoated granules. Yields in plots treated with coated and uncoated chloramben were 3280 and 2700 kg ha−1, respectively. In coated and uncoated linuron plots, yields were 2920 and 2340 kg ha−1, respectively. Except for the uncoated linuron plot, all yields were significantly higher than 2050 kg

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1985.tb00639.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY