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1.
The use of entomopathogenic nematodes on cabbage leaves against larvae of the diamondback moth (DBM) Plutella xylostella requires the addition of formulation adjuvants to achieve satisfying control. Without adjuvants nematodes settle in the tank mix of backpack sprayers causing uneven distribution. The polymers arabic and guar gum, alginate and xanthan were used in concentrations between 0.05 and 0.3% to retard sedimentation of Steinernema carpocapsae. Arabic gum had no effect, guar gum prevented sedimentation at 0.3% but the effect dropped significantly at lower concentration. At 0.05%, xanthan prevented nematode sedimentation better than alginate. Deposition of nematodes on the leaves was significantly increased by the addition of any of the polymers. Spraying nematodes on leaves with an inclination of 45° without the addition of any formulation resulted in 70% run-off. Adding 0.2% alginate or xanthan reduced the losses to <20%. The use of a surfactant–polymer formulation significantly reduced defoliation by DBM larvae. Visual examinations provided evidence that nematodes are not ingested by DBM larvae. Invasion of S. carpocapsae is an active process via the anus. The function of the formulation is not to prolong nematode survival, but to provide environmental conditions which enable rapid invasion of the nematodes. Nematode performance was improved by selection of the best surfactant in combination with xanthan and by optimisation of the concentrations of the surfactant Rimulgan® and the polymer xanthan. The best control results were achieved with Rimulgan® at 0.3% together with 0.3% xanthan, causing DBM mortality of >90% at 80% relative humidity and >70% at 60%. The formulation lowered the LC50 from 12 to 1 nematode/larva. The viscosity of the surfactant–polymer formulations correlated well with nematode efficacy, prevention of sedimentation and adherence to the leave. This physical parameter can therefore be recommended for improvement of nematode formulations to be used for foliar application against DBM. 相似文献
2.
Concentrations of soluble aluminum (Al) and manganese (Mn) frequently reach phytotoxic levels in acid soils. While dose response relationships for these metals are well documented, the effects of combined exposure have received less attention. We have examined the effect of combinations of Al and Mn on growth and metal accumulation in Vigna unguiculata (L.) Walp. grown in solution culture under conditions of low ionic strength (conductivities typically < 100 µS cm−1 ). The nature of interaction between these metals varied with the specific physiological response, the part of the plant investigated, and the relative amount of stress imposed. Analysis of growth data provided evidence for amelioration of metal toxicity (antagonistic effects), although this effect was dose dependent. Analysis of metal content data provided evidence for antagonistic and synergistic (exacerbation of toxicity) effects, again depending on dose. Analysis of foliar symptoms also provided evidence for antagonisms and synergisms, with the nature of the response dependent on the specific physiological response and specific plant part investigated. In contrast with previous reports, evidence for antagonistic, synergistic, and multiplicative effects on growth, metal uptake, and expression of foliar symptoms have been obtained under physiologically and environmentally relevant conditions. These results suggest a more detailed analysis of the potential for interactions between metals in the environment is required. 相似文献
3.
A series of eight experiments was conducted using large pots to (1) find the most effective date, site, concentration of K-solution
and K-salt for foliar K-fertilization of maize plants (Zea mays, L.) grown with sufficient K-supply in soil, (2) explain why maize responded to the K-treatment, and (3) examine the influence
of various levels of N and P supplies on the effectiveness of K-fertilizer via the leaves.
A single spraying on sweet maize and field maize on any day between 50% tasselling date to 10 days after tasselling shortened
maturity date, increased grain yield, stover yield, grain-stover ratio, absorption of N, P, K, Ca and Mg, sweetness of young
grain (of sweet maize), and crude protein content of grain. However spraying on the third day after 50% tasselling was most
effective. The second application later than 7 days after the 50% tasselling date suppressed the effects of spraying on the
most effective date. In application of many repetitive sprayings covering the most effective date, a spraying program with
late spraying could reduce grain yield. KNO3, 2.5% KNO3-solution, and applications on all aerial parts were found to be the most effective. Increases in grain yield for spraying
on all aerial parts, spraying on ear leaf only, spraying on all leaves above ear leaf and applying K to soil were 74%, 51%,
41% and 23%, respectively. The foliar K-fertilization affected maize by stimulating chlorophyll synthesis and not by increasing
leaf area. A balance in N and K supplies was determined to be effective for the K-fertilization. 相似文献
4.
Many soybean [Glycine max (L.) Merr.] genotypes that are grown in solution cultures are highly sensitive to the combination of both salinity and inorganic
phosphate (Pi) in the substrate. This effect has been observed on numerous occasions on plants grown in a saline medium that
contained a substantial amount of Ca (i.e., CaCl2/NaCl=0.5 on a molar basis). Because Ca is important in regulating ion transport and membrane permeability, solution culture
experiments were designed to examine the effects of various concentrations of Pi and ratios of CaCl2/NaCl (0 to 0.5 on a molar basis) at a constant osmotic potential (−0.34 MPa) on this adverse interaction. Four soybean cultivars
(‘Lee’, ‘Lee 74’ ‘Clark’ and ‘Clark 63’) were tested.
No adverse salinity x Pi interaction was found on Lee at any ratio and leaf P and Cl were maintained below 300 and 200 mmol
kg−1 dry wt, respectively. Clark, Clark 63 and Lee 74 soybean plants, on the other hand, were severely injured by solution salinity
(−0.34 MPa osmotic potential) when substrate Pi was ≥0.12 mM. Reduced substrate Ca did not intensify the salinity x Pi interaction. On the contrary, the onset of injury was hastened
and more severe with increased CaCl2/NaCl ratios in isotonic solutions. Shoot and root growth rates decreased as injury increased. Leaf P concentrations from
these cultivars grown in saline solutions with 0.12 mM Pi were excessive (>600 mmol kg−1 dry wt) compared with concentrations commonly found in soybean leaf tissue yet they were independent of the severity of injury.
Since leaf Cl increased wiht increased CaCl2/NaCl ratio, we suspect that the severity of foliar injury was related to the combined effects of excessive P and Cl within
the tissue. Lee 74, the only injured cultivar examined that excluded Cl from its leaves, was less sensitive than either Clark
cultivar and its injury was characteristically different. Other ion interactions were reported that may have played a role
in injury susceptibility. 相似文献
5.
Cryopreservation of Digitalis lanata Ehrh. cell cultures: Preculture and freeze tolerance 总被引:4,自引:0,他引:4
Cryopreservation experiments were performed with Digitalis lanata cell cultures. The main stress was laid on the behaviour of the cells during the preculture period and the capacity of various preculture additives to induce freeze tolerance. The following compounds were used as preculture additives: trehalose, mannitol, sucrose, melibiose, proline, and sorbitol. They are listed in the order of their respective efficiency. Using trehalose, high post-thaw viability rates were achieved and the cells resumed growth after a short lag period. Melibiose was used as a preculture additive for the first time. Its suitability was in the range of that of sucrose. Proline and sorbitol were not able to induce freeze tolerance in Digitalis cells. Cell viability showed a considerable decrease at the beginning of the preculture period. This reduction was found to be transient in the presence of trehalose, mannitol, sucrose, and melibiose. The damaging effects of proline and sorbitol were too severe to be compensated for by the cells. The PAL activity increased markedly in the presence of proline, whereas the trehalose-treated and the control cells behaved nearly identical to one another. 相似文献
6.
植物附生微生物与叶部病害生物防治研究进展 总被引:11,自引:0,他引:11
人们早已发现绿色植物叶面(phylloplane)栖居有大量微生物。在一百多年前微生物学家就从植物叶面分离到许多真菌和细菌。1910年Potter首先证实,叶面附生微生物在干扰真菌引起的叶部病害中起着重要作用。至本世纪上半叶,叶面微生物仍为人们所忽视。相反,在这期间土壤微生物得到很大发展,在土传植物病原菌生物防治研究方法上取得了很大进展,为后来的植物叶部病害生物防 相似文献
7.
A Osuna G Ortega F Gamarro S Castanys M C Mascaro 《International journal for parasitology》1984,14(3):253-257
The penetration of metacyclic forms of Trypanosoma cruzi into HeLa cells after different treatments was studied. When cell development was synchronized by two different processes, maximum rates of parasitization occurred during the S phase of cell cycle (29.48 and 24.3%). However, when cells were treated with trypsin (0.1%), parasitization rates appeared to be lower than controls, reaching values similar to controls 14 h after the beginning of the treatment. Infection values remained unaltered after treatment with colcemid (0.6 μg ml?1). Cell treatment either with valinomycin (1 μg ml?1) or with actinomycin D (250 μg ml?1) caused a marked decrease in the percentage of parasitization. When cells were treated and infected in the presence of tunicamycin (100 ng ml?1), parasitization rates were increased (14.7%) compared to control cells (6%). On the other hand, no differences in parasitization rates were observed when cells were treated with cycloheximide (100 μg ml?1). Infection in a low redox medium (?100 mV) resulted in considerable increase in parasitization. 相似文献
8.
J.M. Jandal 《Small Ruminant Research》1996,20(3):275-279
The effects of heating (20, 37 or 50 °C), cooling (5 °C), pasteurisation (71 °C for 15 s), boiling (100 °C), agitation (5 or 10 min), pH (acid or alkaline), and addition of chemicals such as silver and lead nitrates, copper sulphate and sodium chloride on lipase activity in Shammi goat milk were studied. There were non-significant differences (P < 0.01) in chemical composition between Shammi goat milk and Arabi cow milk. Lipase activity in Shammi goat milk was non-significantly (P < 0.01) lower than in Arabi cow milk. Lipase activity in milk of Shammi goats and Arabi cows was reduced when the milk was subjected to heating, cooling, pasteurisation, boiling, or when chemicals or acid was added, whereas in agitated and alkaline milk, the lipase activity was increased. The increase following agitation was greater after 10 min than 5 min. It can be concluded that heating, pasteurising, boiling, cooling, addition of certain chemicals and acidity are means by which lipase activity in milk can be reduced. 相似文献
9.
Ülo Niinemets 《Ecological Research》1996,11(3):269-281
Dependencies of foliage arrangement and structure on relative irradiance and total height (TH) were studied in saplings ofAcer platanoides andQuercus robur. The distribution of relative foliar area and dry weight (leaf area and weight in a crown layer per total tree leaf area
and weight, respectively) were examined with respect to relative height (RH, height in the crown per TH) and characterized
by the Weibull function. The distributions of relative area and weight were nearly identical, and the differences between
them were attributable to a systematic decline in leaf dry weight per area with increasing crown depth. Foliage distribution
was similarly altered by tree size in both species; RH at foliage maximum was lower and relative canopy size (RCS, length
of live crown per TH) greater in taller trees. However, the distribution was more uniform inA. platanoides than inQ. robur. Apart from the size effects, relative irradiance also influenced canopy structure; RCS increased inQ. platanoides and decreased inQ. robur with increasing irradiance. As crown architecture was modified by irradiance, foliage distribution was shifted upwards with
decreasing irradiance inA. platanoides, but it was independent of irradiance inQ. robur. Higher foliage maximum at lower irradiance in more shade-tolerantA. platanoides is likely to contribute towards more efficient foliar display for light interception and increase the competitive ability
of this species in light-limited environments. Consequently, these differences in crown architecture and foliage distribution
may partly explain the superior behavior ofA. platanoides in understory. 相似文献
10.