Malaria-induced reduction of fecundity during the first gonotrophic cycle of Anopheles Stephensi mosquitoes

Abstract. Anopheles stephensi mosquitoes which had fed upon mice infected with Plasmodium yoelii nigeriensis malaria parasites produced significantly fewer eggs than mosquitoes fed on an uninfected mouse. Fecundity reduction was more pronounced when the bloodmeal contained malaria gametocytes and the mosquitoes developed oocysts. Egg production and haematin excretion were correlated for uninfected bloodfed mosquitoes; the presence of P.y. nigeriensis in the blood affected this relationship. Reduced fecundity was associated with a significant reduction of bloodmeal size (measured by haematin excretion) in mosquitoes which ingested gametocytaemic blood. The bloodmeal size in mosquitoes fed on parasitaemic blood without gametocytes was not significantly reduced. The use of haematin assays for determination of bloodmeal size in mosquitoes is discussed.     

Diversity of carbon use strategies in a kelp forest community: implications for a high CO2 ocean

Mechanisms for inorganic carbon acquisition in macroalgal assemblages today could indicate how coastal ecosystems will respond to predicted changes in ocean chemistry due to elevated carbon dioxide (CO₂). We identified the proportion of noncalcifying macroalgae with particular carbon use strategies using the natural abundance of carbon isotopes and pH drift experiments in a kelp forest. We also identified all calcifying macroalgae in this system; these were the dominant component of the benthos (by % cover) at all depths and seasons while cover of noncalcareous macroalgae increased at shallower depths and during summer. All large canopy‐forming macroalgae had attributes suggestive of active uptake of inorganic carbon and the presence of a CO₂ concentration mechanism (CCM). CCM species covered, on average, 15–45% of the benthos and were most common at shallow depths and during summer. There was a high level of variability in carbon isotope discrimination within CCM species, probably a result of energetic constraints on active carbon uptake in a low light environment. Over 50% of red noncalcifying species exhibited values below ?30‰ suggesting a reliance on diffusive CO₂ uptake and no functional CCM. Non‐CCM macroalgae covered on average 0–8.9% of rock surfaces and were most common in deep, low light habitats. Elevated CO₂ has the potential to influence competition between dominant coralline species (that will be negatively affected by increased CO₂) and noncalcareous CCM macroalgae (neutral or positive effects) and relatively rare (on a % cover basis) non‐CCM species (positive effects). Responses of macroalgae to elevated CO₂ will be strongly modified by light and any responses are likely to be different at times or locations where energy constrains photosynthesis. Increased growth and competitive ability of noncalcareous macroalgae alongside negative impacts of acidification on calcifying species could have major implications for the functioning of coastal reef systems at elevated CO₂ concentrations.     

An Effect of pH and Bicarbonate on Salt Accumulation by Disks of Storage Tissue

1. The uptake of potassium chloride by disks of several storagetissues has been determined from solutions at alkaline pH valuesand compared with that form solutions at pH 6.5. The stimulationof cation uptake under the alkaline conditions which has previouslybeen obtained with beet tissues was observed with some of thesetissues to a greater or lesser extent. 2. It is concluded that it is the accumulation of anions present in alkaline solutions which generally promotesthe uptake of cations; tissues which do not show the ‘pHeffect’ accumulate very little in the presence of the Cl^- anion. 3. In some cases the alkaline pH values also stimulated anionuptake. This was especially true in artichoke in which the absorptionof both ions was stimulated by approximately the same amount.It is concluded that this represents either a true pH effector a direct effect of anions on the overall salt sccumulation mechanism rather than an indirect effect throughorganic acid synthesis. 4. The experiments reveal a cation/anion ratio of approximatelyI:I when the uptake of ions is taken into consideration. It is suggested that this ratio may be more frequent then isgenerally accepted and that the uptake of CO₂ (converted toan anion in the tissue) may take the place ions at lower pH values. 5. The deleterious effects of frequently observed on growth contrast with the stimulations of salt absorptionobtained here; the rapid increase in the concertration of cationsand/or organic acid anions associated with HCO uptake may insome way be responsible for this.     

The Effect of an Incandescent Supplement on the Growth of Tomato Plants in Low Light

Young tomato plants were grown at low light flux densities (21W m^-2 for 8 h days) in growth cabinets under three types offluorescent lamps or under a fluorescent/incandescent mixedsource. Whilst net assimilation rates under the fluorescentlamps were in agreement with those calculated from the lampcharacteristics and the photosynthetic action spectrum, therate under the mixed source was about 20 per cent higher thanexpected. Relative growth rates and relative leaf area growthrates were also higher and leaf area ratios lower under thefluorescent/incandescent lamp combination than under the purefluorescent sources. Small differences in stem elongation, leaftemperature and dry weight distribution which were associatedwith the addition of incandescent radiation were not consideredto be responsible for these increases. When the light flux densityfrom the mixed source was reduced by 20 per cent, the plantgrowth parameters were then similar to those in fluorescentlight alone.     

Effect of Light Intensity, Carbon Dioxide Concentration, and Leaf Temperature on Gas Exchange of Spray Carnation Plants

The rates of CO₂ assimilation by potted spray carnation plants(cv. Cerise Royalette) were determined over a wide range oflight intensities (45–450 W m^–2 PAR), CO₂ concentrations(200–3100 vpm), and leaf temperatures (5–35 °C).Assimilation rates varied with these factors in a way similarto the response of single leaves of other temperate crops, althoughthe absolute values were lower. The optimal temperature forCO₂ assimilation was between 5 and 10 °C at 45 W m^–2PAR but it increased progressively with increasing light intensityand CO₂ concentration up to 27 °C at 450 W m^–2 PARand 3100 vpm CO₂ as expressed by the equation TOpt = –6.47-h 2.336 In G + 0.031951 where C is CO₂ concentration in vpmand I is photo-synthetically active radiation in W m^–2.CO₂ enrichment also increased stomatal resistance, especiallyat high light intensities. The influence of these results on optimalization of temperaturesand CO₂ concentrations for carnation crops subjected to dailylight variation, and the discrepancy between optimal temperaturesfor growth and net photosynthesis, are discussed briefly     

The effect of partial flower removal on the relation betwen root, shootand fruti growth in the indeterminate tomato

The root, vegetative shoot and fruit growth of November and January sown glasshouse tomato plants grown in flowing water culture was followed over 6–7 months. The relationship between vegetative and reproductive growth was examined after two-thirds of the flowers were removed from half the experimental plants. This resulted in larger plants which had fewer, larger fruits and eventually a fruit yield almost as large as the controls. In the control plants, fruit growth increased steadily until it reached 90% of the total incremental fresh weight of the plant 50–60 days after first anthesis. Leaf growth was markedly depressed at this stage and root growth ceased 4 wk after anthesis. Some root death was observed from anthesis onwards. When fruit growth subsequently diminished, vegetative growth recovered but to a lower rate than before fruiting commenced. Following partial flower removal, only 64% or less of the total increment of fresh weight went into the fruit. Although vegetative growth at this stage was thus greater than in the control plants, both shoot and root growth followed the same qualitative pattern with time. The ratio of vegetative shoot to root fresh weight remained essentially constant throughout the fruiting phase in plants of both sowings whether flowers were removed or not. This suggests that the fruit grew in competition with the vegetative organs as a whole, although, for a short period at early fruiting, root growth was more seriously affected. The pattern and amount of fruiting in this indeterminate plant was influenced by the size of the vegetative organs at fruiting, and by the effect of the existing developing fruit on further vegetative and reproductive growth.     

The Effect of pH and Bicarbonate Ions on the Uptake of Salts by Disks of Red Beet

1. The uptake of potassium chloride by disks of beetroot in solutionsat different pH values has been followed over periods of severaldays.
2. It was found that, as the pH was raised from approximately6to 9 the rate of uptake of potassium from 0.0024 M. potassiumchloride increased, and there was a corresponding increase inthe amount of potassium held by the disks at satura tion. Boththe rate of uptake and the final content of potassium in diskskept in solutions at pH 8.5 were frequently double those atpH 6.
3. The rate of uptake of chloride ions was only slightlyaffectedby the pH value of the medium. The final chloride contentwasapproximately the same in disks kept at different pH values.
4. The above ‘pH effect’ on potassium uptake hasbeenshown to be related to the uptake of bicarbonate ions presentin the alkaline solution; the additional potassium ions accumulatedaccompanying the bicarbonate anions taken up.
5. The bicarbonateions accumulated are converted primarily tomalic acid.

     

Effect of Night Temperature on Photosynthesis, Transpiration, and Growth of Spray Carnations

Spray carnation plants were grown for several weeks under an8 h day/16 h night regime at temperatures of approximately 21°C by day and 6, 17, or 30 °C by night. Subsequently,the rates of photosynthesis and transpiration at 20 °C weresimilar. This contrasts with evidence published for some otherspecies. Night temperature had only a slight effect on the plant's growthrate. Leaf area ratios were also similar between treatmentsand for two intervals covering a 5 week period. At the highnight temperature flowers were initiated sooner and there werefewer side shoots per plant than at the lower temperatures. The implications of these results for the optimization of theclimatic environment are discussed briefly, and the resultsare compared with those reported for other species.