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Showing papers by "Adrian C. Newton published in 1993"


Journal ArticleDOI
TL;DR: It is suggested that an integrated method of pest management might be achieved by the incorporation of pest resistant planting stock in silvicultural systems which encourage natural biological control.

142 citations


Journal ArticleDOI
TL;DR: Preliminary results suggest that dipterocarp seedlings may only be responsive to fertilizer addition when grown at very low nutrient availabilities, and that ECM infection may be of great importance to seedling growth under such conditions.

75 citations



Journal ArticleDOI
TL;DR: It is suggested that any conservation strategy developed for mahoganies should include a genetic selection and improvement programme as well as the protection of natural stands in situ.
Abstract: Mahoganies (Swietenia spp; Meliaceae) are amongst the most economically important tropical hardwoods, and yet little information exists concerning their patterns of genetic variation The characterization of this variation is essential for defining more accurately the conservation status of mahogany populations, and for their economic utilization The loss of genetic variation through deforestation may be critical for these species, which are highly susceptible to pest attacks when grown in plantations This paper assesses the current state of knowledge concerning the extent of genetic variation in mahoganies, and highlights its potential importance It is suggested that any conservation strategy developed for mahoganies should include a genetic selection and improvement programme as well as the protection of natural stands in situ Techniques by which particular genotypes may be captured for ex situ conservation are briefly described

32 citations


Journal ArticleDOI
TL;DR: Results support the suggestion that leafy cuttings actively photo- synthesize during propagation, by measurement of stomatal conductance, relative water content (RWC) and water potential during the first three weeks after insertion in the propagators.
Abstract: Variation in the water status of leafy cuttings of four tropical tree species was assessed in both mist and non-mist propagation systems, by measurement of stomatal conductance, relative water content (RWC) and water potential during the first three weeks after insertion in the propagators. Significant water deficits developed in all four species, with a minimum water potential of -3.1 MPa recorded for Triplochiton scleroxylon K. Schum. However, unrooted cuttings in both propagation systems were able to recover turgor, with peak RWCs over 90% recorded for all four species. Stomatal conductances were generally above 0.4 cm s-’, with a maximum of over 1.2 cm s“' recorded for Terminalia spinosa Engl. These results support the suggestion that leafy cuttings actively photo- synthesize during propagation. The two propagation systems had a contrasting effect on the water status of the cuttings, but this effect differed between the two experiments, and there was no overall effect of propagation system on rooting ...

30 citations


Journal ArticleDOI
TL;DR: In this article, the microclimates of two contrasting propagation systems, a polyethylene-covered mist unit and a low-technology, non-mist polymethylene propagator, were examined in detail over a two year period.
Abstract: The microclimates of two contrasting propagation systems, a polyethylene-covered mist unit and a low-technology, non-mist polyethylene propagator, were examined in detail over a two year period. Both systems were able to maintain relative humidities (r.h.) of over 90% for much of the time; r.h. below 60% was associated with peaks in irradiance of over 1000 nmol m'2 s'1. Leaf-to-air vapour pressure difference (VPD) tended to vary in a manner similar to irradiance, remaining close to zero during night, and often reaching values over 3.0 kPa during early afternoon. Maximum VPD in the non-mist system was associated with opening of the propagator lid, which caused an immediate decline in r.h. When the propagator lid was kept closed, VPD under mist was consistently 2-3 times higher than under non-mist. The relationship between VPD and irradiance was found to vary both diurnally and from week to week. In general, a large part of the variation in VPD was unaccounted for by irradiance, as air temperature in both s...

25 citations


Journal ArticleDOI
TL;DR: Three-component mixtures of two barley cultivars expressing partial resistance to mildew with the third component either expressing complete resistance or a defeated major gene gave more yield than the mean of their components in monoculture in a series of field trials.
Abstract: Three-component mixtures of two barley cultivars expressing partial resistance to mildew (Erysiphe graminis f. sp, hordei) with the third component either expressing complete resistance or a defeated major gene gave more yield than the mean of their components in monoculture in a series of field trials. However, there was no reduction in mildew infection in the mixtures and even a significant increase in one trial. The potential for using partially resistant cultivars in mixtures is discussed

10 citations


Journal ArticleDOI
TL;DR: Seedling leaves of four cultivars of barley were inoculated with powdery mildew and enclosed in an apparatus which enabled accurate control of humidity, air speed and temperature, showing greater reduction in infection frequency and more reduction in biomass per colony under low humidity than the other cultivars.
Abstract: Seedling leaves of four cultivars of barley, three of which express partial resistance, were inoculated with powdery mildew (Erysiphe graminis f.sp. hordei) and enclosed in an apparatus which enabled accurate control of humidity, air speed and temperature. Infection frequency was always greater at high humidity (> 95%) than at low humidity (40-50%). Cultivar 7204 (Ethiopian) showed a greater reduction in infection frequency at both 12 and 16°C, and more reduction in biomass per colony at 16°C under low humidity than the other cultivars. The potential for exploiting such differences in barley breeding is discussed

7 citations


Journal ArticleDOI
TL;DR: The results indicate the severity of the transplant shock in semi-arid sites for seedling water status, and imply that initial irrigation treatments are more likely to increase establishment rates of tree seedlings than application of synthetic polymers.

3 citations