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21.
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
22.
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
23.
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
24.
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.
25.
A dual-surface leaf chamber was used to investigate the responsesof net photosynthesis and leaf conductance to independent changesin the humidity environments of the upper and lower surfacesof leaves of sunflower and soybean. In sunflower decreasingthe humidity around the upper leaf surface while maintainingthat of the lower surface constant and high reduced both thephotosynthetic rate and the conductance of the lower surface.These reductions could not be attributed to changes in bulkleaf water potential since the transpiration rate of the wholeleaf remained constant. Similarly, the reductions were not relatedto localized water deficits in the lower epidermis or lowermesophyll since the transpiration rate of the lower surfacewas reduced. Possible mechanisms whereby the gas exchange characteristicsof the lower leaf surface of sunflower respond to the humidityenvironment of the upper surface are discussed. In contrastto sunflower, the photosynthetic rate of the lower surface ofsoybean was insensitive to the humidity environment of the uppersurface. In leaves of sunflower grown under a moderate temperature anda medium light level, simultaneous decreases of humidity atboth leaf surfaces reduced the photosynthetic rate of the wholeleaf without affecting the substomatal partial pressure of CO2.In contrast, with leaves developed under a cool temperatureand a high light level, both the photosynthetic rate and thesubstomatal partial pressure of CO2 were reduced. Evidently,the occurrence in sunflower of the response pattern suggestinga non-stomatal inhibition of photosynthesis by low humiditydepends upon the environment during growth. The possibilitythat this non-stomatal inhibition may be an artifact due toan error in the assumption of water vapour saturation withinthe leaf airspace is considered. Key words: Vapour pressure deficit, photosynthesis, conductance, non-stomatal inhibition, Helianthus annuus, Glycine max 相似文献
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29.
M. R. JAMES 《Freshwater Biology》1985,15(3):307-314
SUMMARY.
- 1 A study of the distribution, biomass and production of the freshwater mussel Hyridella menziesi (Gray) was carried out at six sites in Tapuaeharuru Bay, Lake Taupo, New Zealand.
- 21 H. menziesi is common in the littoral zone, with clean sand and angle of slope being the most important environmental variables measured which are positively associated with mussel density. These variables are related to the accumulation of fine material which can clog the filtering mechanism of mussels. The angle of slope may also influence the movement and supply of food.
- 3 Density (5.6 m-2), biomass (2.8 g dry weight shell free tissue m-2) and potential production (0.50 g dry weight shell free tissue m-2 yr-1) are high compared to values found for mussels from other oligotrophic lakes.
- 4 The age structure of Hyridella suggests recruitment has declined in recent years. A periodicity in generations is proposed.
30.
JAMES H. JOHNSON 《Freshwater Biology》1985,15(6):749-755
SUMMARY.
- 1 Diel feeding periodicity and diet composition of nymphs of Aeshna multicolor and Lestes unguiculatus were examined at 6 h intervals in a small pond. Feeding intensity of A. multicolor increased from 06.00 hours to approximately 18.00 hours whereas food intake by L. unguiculatus was uniformly high between 12.00 and 18.00 hours. Feeding of both species was reduced during the night.
- 2 Diel variation in diet composition was substantial in each species. Chironomid larvae were the major prey (48.9%) in the diet of A. multicolor. Zooplankton, mainly cladocerans (42.0%) and ostracods (21.1%), were the principal prey of L. unguiculatus. Detritus composed a substantial portion of the diets of both species.
- 3 Diet overlap (Cλ) at each 6 h interval was high (0.43–0.72) when detritus was included in the calculation and was low (0.48–0.54) when detrital material was omitted.