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11.
The effects of repeated annual application of methiocarb-based slug pellets, broadcast on the soil surface and drilled into the seed bed, on carabid beetle activity were investigated over a four year period on a winter-sown cereal field using pitfall traps in barriered plots. Following applications in late autumn all winter-active carabid populations were severely depressed; total carabid activity falling to less than 5% and 10–15% following broadcast and drilled applications, respectively, compared with untreated plots. Spring and summer-active species, not active at the time of application, were largely unaffected by applications and were responsible for a gradual recovery of total activity from early spring onwards. Activity of all affected winter species remained demonstrably depressed on treated areas for the remainder of their seasonal incidence. However, all except one species, Bembidion obtusum, recovered to normal activity levels in the following season prior to reapplication. Recovery patterns are discussed in terms of the known biology of the species involved. Evidence that a minority of summer-active species were also affected by treatments, sometimes positively and sometimes negatively, were attributed to indirect effects possibly involving prey availability and foraging behaviour. The long-term ecological and short-term agronomic implications of methiocarb effects on carabid populations in winter-sown cereals are discussed. 相似文献
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The Physiology and Nitrogen-fixing Capability of Aquatically and Terrestrially Grown Neptunia plena: The Importance of Nodule Oxygen Supply 总被引:3,自引:0,他引:3
The aquatic legume Neptunia plena (L.) Benth. was grown in non-aeratedwater culture or vermiculite. Growth, nodulation, nitrogen fixationand nodule physiology were investigated. Over an 80-d period,plants grew and fixed nitrogen and carbon equally well in bothrooting media, although distribution of growth between plantparts varied. Total nodule dry weights and volumes were similarbut vermiculite-grown plants had three times as many (smaller)nodules than those grown in water. Oxygen diffusion resistanceof nodules exposed to 21% oxygen and 10% acetylene did not differsignificantly. Both treatments showed similar declines in rootrespiration and acetylene reduction activity (approx. 10%) whenroot systems were exposed to stepped decreases and increasesin rhizosphere oxygen concentration. However, nitrogenase activityof aquatically grown plants was irreversibly inhibited by rapidexposure of nodules to ambient air, whereas vermiculite-grownplants were unaffected. Aeration of water-cultured N. plenareduced stem length (but not mass) and number of nodules perplant. The concentration of nitrogen fixation by 163%. PossibleO2 transport pathways from the shoot atmosphere to roots andnodules are discussed. Aquatic legume, diffusion resistance, Neptunia plena, nitrogen fixation, oxygen, root nodules 相似文献
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The Influence of Carbon Dioxide and Daily Photon-flux Density on Optimal Leaf Nitrogen Concentration and Root: Shoot Ratio 总被引:5,自引:1,他引:4
Using a cost-benefit model, the leaf nitrogen concentrationand root : shoot ratio that maximize whole-plant relative growthrate are determined as a function of the above-ground environment(integrated daily photon flux density and the concentrationof carbon dioxide at the site of fixation within the leaf).The major advantage of this approach is that it determines theadaptive significance of leaf physiology by considering thefunctional integration of leaves and roots. The predicted responseto increasing daily photon flux densities is an increase inoptimal leaf N concentration (Nopt) and a concomitant increasein root: shoot ratio. Increased carbon dioxide concentrations,on the other hand, reduce Nopt and only slightly change root:shoot ratio. The observed increase in leaf nitrogen concentrationfound in plants growing at high altitudes (low CO2 partial pressure)is also predicted. Since these responses to light and CO2 maximizethe whole-plant relative growth rate, the observed adjustmentsthat plants make to light and carbon dioxide concentration appearto be adaptive. We show that the relationship between photosynthesis and leafnitrogen concentration is complex and depends on the light andCO2 levels at which photosynthesis is measured. The shape ofthis function is important in determining Nopt and the oppositeresponse of leaf nitrogen to light and carbon dioxide is shownto be the result of the different effects of light and CO2 onthe photosynthesis-leaf nitrogen curve. Plant growth, photosynthesis, leaf nitrogen, biomass allocation, optimization, carbon dioxide light 相似文献
17.
MILLER ROBYN M.; KAUL VIJAY; HUTCHINSON JAMES F.; MAHESWARAN GOWRI; RICHARDS DENNIS 《Annals of botany》1991,68(6):563-568
Adventitious shoots were regenerated from fragmented flowerbuds, individual petals and receptacles in a number of differentcarnation cultivars. The major site of shoot formation was thesubepidermal cells at the proximal end of the petals. The yieldof shoots from a single flower bud was high, ranging between70 and 275, for the 11 cultivars tested. The regeneration mediumcontained Murashige and Skoog basal medium supplemented with48 µm -naphthaleneacetic acid and 48 µmbenzyladenine. The preferred regeneration protocol appears highlysuited to the development of gene transfer systems. Adventitious shoots, Dianthus caryophyllus L., tissue culture, explant, auxin, cytokinin, cut flowers, floriculture, organogenesis 相似文献
18.
Ruta graveotens subshrubs, known to contain a large fractionof their furanocoumarins on the leaf surface, were used forinvestigation of salt and acid rain effects on the plant surfaceand substances occurring there. Groups of shoots on each plantcovered by plastic bags were sprayed with either sulphuric acid,pII 2.5, saturated sodium chloride solution, or a distilledwater control. Uncovered shoots, an additional control, hadthe highest concentrations of furanocoumarins both on the surfaceand in the whole leaf. The upper leaves contained less furanocoumarinsin absolute amounts but were similar to the lower leaves ona percentage basis. Spraying caused a decrease in total furanocoumarinconcentrations, slight in the case of distilled water and greaterfor acid and salt, but the percentage on the surface after sprayingincreased. The upper and lower leaves reacted differently tosalt than to sulphuric acid and water: with salt, the percentagesof furanocoumarins on the surface of both kinds of leaves showedsimilar increases; with the other two sprays, upper leaves showeda similar increase, but the lower leaves had a much higher percentageon the surface owing to a high rate of extrusion. Simulated acid rain, salt sprays, plant surface, furanocoumarins, Ruta graveolens 相似文献
19.
JAMES B. COUPLAND 《Ecological Entomology》1991,16(1):11-15
Abstract.
- 1 The oviposition behaviour of Simulium reptans L. is described from two sites on the River Spey, Scotland. Female aggregations were observed immediately downstream of oviposition sites and were composed mainly of gravid flies (range 60–80%0) together with smaller numbers that were either freshly bloodfed (range 2–17%) or infected with mermithid nematodes (range 0–30%).
- 2 The time from landing on the oviposition sites to the onset of oviposition was recorded. The time in the presence of greater than 1-day-old eggs did not significantly differ from sites with no eggs present. However, the presence of freshly laid or I-day-old eggs significantly shortened the time to onset of oviposition. The cues that elicit oviposition are unknown but it is speculated that they may involve a pheromone.
20.