Influence of Elevated CO2 and Temperature on the Photosynthesis and Respiration of White Clover Dependent on N2 Fixation

Single clonal plants of white clover (Trifolium repens L) grownfrom explants in a Perlite rooting medium, and dependent fornitrogen on N₂ fixation in root nodules, were grown for severalweeks in controlled environments which provided two regimesof CO₂, and temperature 23/18 °C day/night temperaturesat 680 µmol mol^–1 CO₂, (C680), and 20/15 °Cday/night temperatures at 340 µmol mol^–1 CO₂ (C340)After 3–4 weeks of growth, when the plants were acclimatedto the environmental regimes, leaf and whole-plant photosynthesisand respiration were measured using conventional infra-red gasanalysis techniques Elevated CO₂ and temperature increased ratesof photosynthesis of young, fully expanded leaves at the growthirradiance by 17–29%, despite decreased stomatal conductancesand transpiration rates Water use efficiency (mol CO₂ mol H₂O^–1)was also significantly increased Plants acclimated to elevatedCO₂, and temperature exhibited rates of leaf photosynthesisvery similar to those of C340 leaves ‘instantaneously’exposed to the C680 regime However, leaves developed in theC680 regime photosynthesised less rapidly than C340 leaves whenboth were exposed to a normal CO₂, and temperature environmentIn measurements where irradiance was varied, the enhancementof photosynthesis in elevated CO₂ at 23 °C increased graduallyfrom approx 10 % at 100 µmol m^–1 s^–1 to >27 % at 1170 µmol m^–2 s^–1 In parallel, wateruse efficiency increased by 20–40 % at 315 µmolm^–2 s^–1 In parallel, water use efficiency increasedby 20–40 % at 315 µmol m^–2 s^–1 In parallel,water use efficiency increased by 20–40 % at 315 µmolm^–2 s^–1 In parallel, water use efficiency increasedby 20–40 % at 315 µmol m^–2 s^–1 to approx100 % at the highest irradiance Elevated CO₂, and temperatureincreased whole-plant photosynthesis by > 40 %, when expressedin terms of shoot surface area or shoot weight No effects ofelevated CO₂ and temperature on rate of tissue respiration,either during growth or measurement, were established for singleleaves or for whole plants Dependence on N₂, fixation in rootnodules appeared to have no detrimental effect on photosyntheticperformance in elevated CO₂, and temperature Trifolium repens, white clover, photosynthesis, respiration, elevated CO₂, elevated temperature, water use efficiency, N₂ fixation     

Effects of diet and host access on fecundity and lifespan in two fruit fly species with different life‐history patterns

The reproductive ability of female tephritids can be limited and prevented by denying access to host plants and restricting the dietary precursors of vitellogenesis. The mechanisms underlying the delayed egg production in each case are initiated by different physiological processes that are anticipated to have dissimilar effects on lifespan and reproductive ability later in life. The egg‐laying abilities of laboratory‐reared females of the Mediterranean fruit fly (Ceratitis capitata Wiedmann) and melon fly (Bactrocera cucurbitae Coquillett) from Hawaii are delayed or suppressed by limiting access to host fruits and dietary protein. In each case, this is expected to prevent the loss of lifespan associated with reproduction until protein or hosts are introduced. Two trends are observed in each species: first, access to protein at eclosion leads to a greater probability of survival and a higher reproductive ability than if it is delayed and, second, delayed host access reduces lifetime reproductive ability without improving life expectancy. When host access and protein availability are delayed, the rate of reproductive senescence is reduced in the medfly, whereas the rate of reproductive senescence is generally increased in the melon fly. Overall, delaying reproduction lowers the fitness of females by constraining their fecundity for the remainder of the lifespan without extending the lifespan. © 2013 The Royal Entomological Society     

Interactions between seed priming treatments and nine seed lots of carrot, celery and onion. II. Seedling emergence and plant growth

Samples of three seed lots of each of three cultivars of carrot, celery and onion were primed in polyethylene glycol solution for two weeks at 15 °C. Seedling emergence was recorded in the field for carrot and onion and in the glasshouse for celery. Compared to the untreated control, priming increased the percentage seedling emergence in certain poorly-emerging seed lots of carrot and celery, but had no effect on onion. Mean emergence times were reduced by priming in all seed lots, by 3–5, 5–8 and 3–9 days in carrot, celery and onion respectively. The largest effects occurred in the slowest-emerging seed lots. There were significant interactions between priming and seed lots within cultivars in carrot and celery and between priming and cultivars in celery and onion. Priming generally reduced the spread of emergence times, but the effects were not statistically significant in carrot. Drying back the primed seeds had no effect on percentage emergence in onion, but reduced it (compared to primed seed which had not been dried-back) in certain carrot and celery seed lots. Primed and dried-back seeds emerged later than primed seeds, by up to 1·5, 2·6 and 2·6 days in carrot, celery and onion respectively. The spread of emergence times was generally larger for primed and dried-back seeds than for primed seeds, but the differences were not always statistically significant. Plant fresh weights were recorded 9, 7 and 12 wk after sowing for carrot, celery and onion, respectively. In each species, mean plant weight was inversely related to seedling emergence time; thus plants grown from primed seed were always heavier than the controls, by up to 33%, 182% and 47% in carrot, celery and onion respectively.     

Heterophylly in Ranunculus flabellaris Raf.: The Effect of Abscisic Acid

Ranunculus flabellaris Raf., the Yellow Water-Crowfoot, is aheterophyllous semi-aquatic dicotyledonous plant, showing strikingmorphological and anatomical differences between terrestrialleaves and those formed underwater. After plants are submergedin a 25 µM solution of abscisic acid, leaves are producedat a normal rate but they exhibit many of the characteristicsof terrestrial leaves. Ranunculus flabellaris Raf., Yellow Water-Crowfoot, heterophylly, abscisic acid     

Elevationally biased avian predation as a contributor to the spatial distribution of geometrid moth outbreaks in sub‐arctic mountain birch forest

1. Population dynamics and interactions that vary over a species' range are of particular importance in the context of latitudinal clines in biological diversity. Winter moth (Operophtera brumata) and autumnal moth (Epirrita autumnata) are two species of eruptive geometrids that vary widely in outbreak tendency over their range, which generally increases from south to north and with elevation. 2. The predation pressure on geometrid larvae and pupae over an elevational gradient was tested. The effects of background larval density and bird occupancy of monitoring nest boxes on predation rates were also tested. Predation on larvae was tested through exclusion treatments at 20 replicate stations over four elevations at one site, while pupae were set out to measure predation at two elevations at three sites. 3. Larval densities were reduced by bird predation at three lower elevations, but not at the highest elevation, and predation rates were 1.9 times higher at the lowest elevation than at the highest elevation. The rate of predation on larvae was not related to background larval density or nest box occupancy, although there were more eggs and chicks at the lowest elevation. There were no consistent differences in predation on pupae by elevation. 4. These results suggest that elevational variation in avian predation pressure on larvae may help to drive elevational differences in outbreak tendency, and that birds may play a more important role in geometrid population dynamics than the focus on invertebrate and soil predators of previous work would suggest.     

The distributions of a wide range of taxonomic groups are expanding polewards

Evidence is accumulating of shifts in species' distributions during recent climate warming. However, most of this information comes predominantly from studies of a relatively small selection of taxa (i.e., plants, birds and butterflies), which may not be representative of biodiversity as a whole. Using data from less well‐studied groups, we show that a wide variety of vertebrate and invertebrate species have moved northwards and uphill in Britain over approximately 25 years, mirroring, and in some cases exceeding, the responses of better‐known groups.     

Regeneration and growth of coolibah,Eucalyptus coolabah subsp. arida,a riparian tree,in the Cooper Creek region of South Australia

Abstract Regeneration patterns of Eucalyptus coolabah Blakely & Jacobs subsp. arida (Blakely) L. Johnson & K. Hill (coolibah), a riparian tree of inland Australia, were inferred from size classes at two locations in South Australia; part of the floodplain of Cooper Creek and a swale in the Strzelecki Desert. These had contrasting water regimes; Cooper Creek floods on average once every 5–6 years whereas the swale has a continual water supply from a bore. A peak in size class distribution showed a regeneration event at each location but at different times. The one in the swale was more recent and was dated to the mid-1970s using aerial photography. Young (< 5 m tall) trees, interpreted as recent regeneration, were concentrated on specific topographic features, the top of a steep riverbank and a sand mound separate from the main dune system. Access to these features would have been difficult after flooding suggesting regeneration is dependent on protection from introduced herbivores. Field observations of reproductive status and canopy die-back showed coolibah condition was better in the swale. The relatively poorer condition of floodplain coolibahs was attributed to saline soils compounded by drier conditions rather than age.     

Assessment of body condition in live birds; measurements of protein and fat reserves in the mute swan, Cygnus olor

Condition in animals is often measured in relation to various demands, such as reproduction, migration and cold weather. Usually, indices of protein and fat reserves have to be measured on dead animals. Measurements on live animals enable variations in the condition of individuals to be monitored over time, and can be related to their life histories.
In birds, the size of the breast muscle is the most commonly used measure of protein reserves. A technique for measuring breast muscle thickness was developed, using ultrasound, and was tested on mute swans. The measurements were accurate and highly repeatable. Breast muscle thickness was positively related to the lean dry weight of the breast muscle, and is likely to be a good indicator of total protein reserves.
A system of fat scoring by colour was developed to assess the size of the subcutaneous fat layer. Although the method relies on subjective judgements, the results were highly correlated with the percentage of fat in the subcutaneous layer, and with other measures of fat reserves.
Measurements were made on live, non-breeding swans to monitor seasonal variations in reserves. The seasonal pattern of fat reserves was similar to the normal cycle of weight changes; high in winter and low in summer. There was no change in relation to the moult. No distinct seasonal variation in muscle thickness was found.
There is an unusual pattern of change in the relative size of reserves during emaciation in swans. Muscle reserves appear to be depleted to a greater extent than fat reserves. This is possibly due to the effects of lead poisoning, causing protein necrosis and preventing muscle regeneration.     

Prevention of potato top-roll by aphicide and its effect on leaf area and photosynthesis

In a field of potatoes, top-roll, which is induced by the aphid Macrosiphum euphorbiae feeding on the leaves, was restricted to two rows of plants which accidentally received no phorate aphicide granules at planting. The photo-synthetic rate per unit leaf area and the ground cover of top-rolled leaves were respectively 50% and 20% less than those of normal plants which may account for the smaller yields of affected plants observed in previous experiments.