Transmission properties of an oak canopy in relation to photoperception

Abstract The spectra of incoming daylight and shadelight in a mature oak woodland were measured at intervals during the canopy cycle, and mean transmittance spectra were derived. Transmittance was spectrally neutral at ca. 0.55 during the light phase but, following leaf emergence, transmittance of PAR (400–700 nm) fell to ca. 0.1. Simultaneously, the red : far-red transmittance ratio fell to circa 0.6. Both showed little change during the summer and autumn until senescence, indicating that the optical properties of the canopy were surprisingly stable. There was no evidence that cloud cover influenced mean canopy transmittance, although transient sunflecks introduced great variability which, in combination with sampling bias, might explain previous contradictory reports. The red : far-red fluence rate ratio in the woodland showed a temporary increase in late summer, a result of a small increase in the red : far-red ratio of incoming daylight during this period. Reflectance and transmittance spectra and pigment content of sun and shade leaves were measured. Leaf transmittance spectra showed changes correlated with those of the canopy, and were related to changes in pigment content.     

Interrelations of Flowering and Vegetative Growth in Callistephus chinensis (var. Queen of the Market)

In a study of the effect of photoperiod upon the growth andflowering of Calistephus chinensis (var. Queen of the Market)it has been shown that a one-hour night break of low intensityred light given to plants growing in eight hours daylight canhave a number of morphogenetic effects. In the young plant, such a treatment increased the total areaof the leaf surface and the area per unit weight of leaf material,i.e. the specific leaf area. This effect enabled the treatedplants to make greater use of the incident light, for afternine weeks they were at least 25 per cent heavier than comparableplants which had not had the benefit of the night-break treatment.This treatment also caused flower induction and concomitantstem extension, but transfer back into eight-hour days afteran inductive period accelerated further flower development andrestricted stem extension of both the main axis and the laterals.If flower development was delayed by continuing night breaksor by delaying the onset of induction then more flowers wereeventually formed, but in the very prolific treatments flowersize was reduced. The experiment also indicated that the partition of availabledry weight between leaves, stems, and roots followed a definitepattern dependent only upon total plant dry weight. The diversionof dry weight into flowers was strongly accelerated by transferinto eight-hour days after induction but the remaining dry matterstill appeared to be distributed between the vegetative partsalong the general pattern determined by total vegetative weight. Finally the experiment showed that a wide range of plant formsbearing varying amounts of flowers could be obtained by appropriatetransfers between treatments.     

The Butterflies of Malacca.

THE author has already, in a brief communication (Journ. Linn. Soc. no. 67, vol. xiii. p. 115), given a preliminary notice of two new species of Lepidoptera from Malacca, and mentioned the donor and circumstances which have enabled him to draw up an extended list, with annexed remarks on geographical distribution. It is only necessary to add that the paper, with figures of the new and more remarkable forms, will subsequently appear in the Society's ‘Transactions’     

Isolation and characterization of eight polymorphic microsatellite loci in the rainforest canopy tree,Syzygium sayeri (Myrtaceae)

Eight polymorphic microsatellite loci were isolated from the rainforest canopy tree, Syzygium sayeri, in order to study parentage and subsequently pollen dispersal among individuals in wild populations. Screening of one natural population (n = 64) mapped in a 500 × 500 m area at Cape Tribulation, north Queensland, Australia, yielded two to 11 alleles per locus with observed levels of heterozygosity ranging from 0.07 to 0.70. One locus was significantly out of Hardy–Weinberg equilibrium after Bonferroni correction for multiple tests. These loci should provide a useful tool in further understanding the dispersal patterns of this species.     

Response of Leaf Spectral Reflectance in Loblolly Pine to Increased Atmospheric Ozone and Precipitation Acidity

Leaf reflectance responses to increased ozone and precipitationacidity were determined at visible (400–720 nm) and infra-red(720–2500 nm) wavelengths for field-grown seedlings ofloblolly pine (Pinus taeda L.). Treatments were maintained continuouslyfrom 3 April to 3 November. In a relatively ozone-sensitivevariety of pine, increased ozone decreased visible and infra-redreflectance by late May. By late August, continued exposureto ozone increased visible and infra-red reflectance. As oflate November, ozone at 17ambient or greater concentrationshad increased visible reflectance substantially in an ozone-insensitiveas well as the ozone-sensitive variety. Acidic precipitationdecreased visible and infra-red reflectances in both varietiesin May and decreased infra-red reflectances in the ozone-sensitivevariety in August, but did not produce significant reflectanceresponses in November. Visible reflectance responses to ozoneand acidic precipitation, particularly those near 700 nm, werespectrally similar to reflectance responses reported previouslyfor other deleterious environmental influences. Key words: Pinus taeda, reflectance, ozone, acidic precipitation     

Effects of soil incorporation on the efficacy of the rhabditid nematode, Phasmarhabditis hermaphrodita, as a biological control agent for slugs

The effects of soil cultivation immediately after application of the rhabditid nematode, Phasmarhabditis hermaphrodita , to the soil surface were investigated in two field experiments. The first experiment was done in mini-plots separated by barriers, with an artificially introduced population of slugs ( Deroceras reticulatum ). Nematodes were applied as a drench at a rate of 3 times 10⁹ ha^-1 in one of two application volumes and then left undisturbed or incorporated into the soil by cultivation to 2 cm or 10 cm depth. Moist soil conditions were maintained by irrigation throughout the experiment. Nematode application significantly reduced slug damage to Chinese cabbage seedlings throughout the 7 wk duration of the experiment and the population of D. reticulatum in soil 7 wk after treatment. However, soil cultivation had no effect and did not interact with the effect of nematodes. In the second experiment, in a crop of winter wheat, nematodes were applied to soil by hand-lance at a rate of 3 times 10⁹ ha^-1 and left undisturbed on the soil surface or incorporated by spring-tine cultivation to a depth of 2, 5 or 10 cm. In this experiment, nematodes were applied to dry soil. Cultivation alone had no effect. Nematode application reduced slug damage to wheat plants in plots where nematodes were incorporated into the soil, but not where they were left on the surface. There was no detectable impact of nematodes on slug populations in the wheat experiment.     

Developmental plasticity in a meristic character: the number of tentacles in the lophophore of a bryozoan species

There is increasing interest among evolutionary biologists in developmental plasticity. Previously ignored by many as being irrelevant to evolution because a plastic response to an environmental change is not inherited, the current, more positive, view of plasticity focuses on the fact that, although any individual plastic response is nonheritable, the overall pattern of developmental response to environmental variation (i.e. the developmental reaction norm) is heritable and may vary among genotypes within a population. Characters subject to plastic variation, like those that are entirely genetically determined, may vary in continuous, meristic or discrete ways. Of these, the least work has been carried out on meristic variation. In the present study, we contribute to the rectification of this imbalance by examining the plastic response of the number of tentacles in the lophophore of a species of bryozoan, Membranipora membranacea, to three environmental variables: temperature, salinity and food concentration. Because the approach taken was an experimental one, unlike the majority of studies of bryozoan tentacles to date, we are able to make statements about the causality of variation in tentacle number. The main conclusions of the present study are: (1) that plastic responses occur to all three environmental variables; (2) that these are part of a more generalized plastic response in the overall development of the zooids rather than being lophophore‐specific; and (3) that the issue of whether the relevant developmental reaction norms are adaptive or not is an open (and interesting) question. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 541–551.