Development of a hydrothermal time model that accurately characterises how thermoinhibition regulates seed germination.

Thermoinhibition is the decline in germinability within a seed population as soil temperatures increase above the optimum for germination. Hydrothermal time (HTT) models have been developed that describe the thermoinhibition response as a function of increases in the threshold water potential for seed germination [seed base water potential, Ψ(b) (G)]. Although these models assume a normal distribution of Ψ(b) (G) and a linear upward shift in Ψ(b) (G) with increasing temperature, little research has tested these assumptions. Using germination data obtained from four unrelated plant species, we fitted HTT models that use the Weibull and normal distribution to describe Ψ(b) (G) and compared the accuracy and bias of these two HTT models. For all four species, Ψ(b) (G) and germination were more accurately described by the Weibull than the normal distribution HTT model. At supra-optimal temperatures, Ψ(b) (G) of the earliest germinating seeds showed little thermoinhibition effect so that the seeds germinated very rapidly under moist conditions. However, for the rest of the population, Ψ(b) (G) increased progressively in response to supra-optimal temperatures so that the slower germinating seeds were thermoinhibited. The fitted HTT models reveal aspects of seed thermoinhibition that appear to have adaptational value under variable conditions of soil temperature and moisture.

Using differential responses to light spectra as a monitoring and control tool for Arhopalus ferus (Coleoptera: Cerambycidae) and other exotic wood-boring pests.

Several longhorn beetles (Cerambycidae) and bark beetles (Scolytinae) have been accidentally introduced to New Zealand and are now widespread and abundant. In particular Arhopalus ferus (Mulsant) represents a significant quarantine risk for export timber. Because of this risk timber is fumigated with methyl bromide. Six different light traps baited with different colors (yellow, red, green, white, UV-black light [UV-BL], and UV-black-light-blue [UV-BLB]) were investigated for their population monitoring potential and as a push-pull (incorporating mass trapping) alternative control technique. UV-BLB light traps captured an order of magnitude more A. ferus (122 individuals per night) than yellow light traps (eight individuals per night). The bark beetles Hylurgus ligniperda (F.) and Hylastes ater (Paykull) were most attracted to UV-BL lights that captured 2-4 times more beetles than traps baited with other wavelengths. Results suggest that light traps provide a sensitive method for population monitoring. The responses of these wood borers and bark beetles to different colored light traps provide an opportunity to apply a push-pull control technique. The management of these species could be improved by minimizing the visual attractiveness (push) of wood processing facilities through a conversion to low intensity yellow site lighting, combined with the strategic placement of UV light traps for mass-trapping of residual populations (pull). Light management on its own is unlikely to eliminate the quarantine risk entirely; however, it is likely to reduce populations substantially and contribute toward the aim of reducing methyl bromide use.

Very low maternal plasma alpha-fetoprotein concentration. An indication for follow-up.

In the course of a screening programme for the detection of fetal neural tube abnormalities by measurement of maternal plasma alpha-fetoprotein (AFP), 57 patients were identified who had plasma AFP levels of less than 7 units/ml at 15-20 weeks gestation. follow-up at the time of screening included requests to confirm that the patient was pregnant and also to repeat the AFP test. Tow patients were lost to follow-up and of the remaining 55, 17 patients (31 per cent) were subsequently shown not to have a live fetus and 31 patients (56 per cent) had incorrect estimates of gestation. No particular reason for the very low plasma AFP could be identified in the other seven patients.

Social effects of genetic counselling.

In a follow-up study of 104 subjects referred for genetic counselling between 1965 and 1969 all were at risk of having children with a variety of serious genetic disorders. Most subjects were in social classes III and IV, were married, in their late 20s, and already had an affected child. Sixty-three per cent. were referred by hospital consultants, 27% by their general practitioners, and 10% were self-referrals. All of those counselled appeared to have appreciated the genetic implications, although four overestimated the risks and 11 underestimated the risks.Of those at high risk (greater than 1 in 10) of having an affected child 10 out of 55 couples "planned" further pregnancies despite the risks. In two this was because they had been unable to adopt a child, in four because they had no living children and the disorders in question usually resulted in stillbirth or death in infancy so that the "burden" of an affected child would be of relatively short duration, and one mother had had antenatal diagnosis and selective abortion. Most of the couples in the low-risk group (less than 1 in 20) were reassured and planned further pregnancies.