Totipotency in Tissue Explants and Callus of Some Members of the Liliaceae, Iridaceae, and Amaryllidaceae

In vitro responses of twelve species of bulbs and conns werecompared. Plantlets could be induced directly without interveningcallus on stem tissue in nine species, on ovary tissue in fivespecies, and on leaf tissue in four species. In Gladiolus, Hyacinthus,Muscari, Ornithogahim, and Scilla plantlets were formed withoutgrowth factors added to the Murashige and Skoog medium. In Hippeastrum,Schizoslylis, Sparaxis, and Ipheion auxin was required. No plantletscould be induced directly on explants of growing tissue of Freesia,Tulipa, or Narcissus. Adventitious plantlets could be inducedon pieces of bulb or corm from ten species but such materialwas difficult to free from contamination. Callus was obtained from all species except Tulipa and Hippeastrum.Plantlets could be regenerated from callus except that of Gladiolus,Sparaxis, and Schizostylis. Differences in responses of the twelve species tend to cut acrossthe three families and no simple relation is evident betweenthe natural rate of vegetative increase and the in vitro behaviour.     

Growth and Development in the Young Tomato: I. THE EFFECT OF TEMPERATURE AND LIGHT INTENSITY ON GROWTH OF THE SHOOT APEX AND LEAF PRIMORDIA

Tomato seedlings were grown at constant temperatures of 25°and 15° C. in a 12-hour day at light intensities of 1,600,800, and 400 f.c. The rate of increase in size of the shootapex and the rates of formation and growth of leaf primordiaduring the vegetative phase were followed by dissecting samplesfrom the time of cotyledon emergence onwards. The rate of enlargement of the shoot apex increased with lightintensity, but apical enlargement was delayed at the highertemperature, the delay being longer the lower the light intensity.The rates of leaf formation and leaf growth increased with bothtemperature and light intensity. Temperature had a larger effecton leaf growth than on leaf formation. More leaves were formedbefore flowering at 25° C. than at 15° C., the increasein leaf number being greater the lower the light intensity. It is suggested that the delay in the enlargement of the apexat high temperature can be explained in terms of competitionfor assimilate, the competitive potential of the expanding leafprimordia exceeding that of the apex at higher temperatures.     

Evaluation of some coccinellid species for the biological control of aphids in protected cropping

Four species of Coccinellidae, Adalia bipunctata (L.), Coccinella septem-punctata L., Coelomegilla maculata de G. and Cycloneda sanguinea L., were compared as predators of aphids on cucumbers and chrysanthemums. In laboratory feeding tests C. maculata and C. sanguinea proved the most voracious but the former could not remain on cucumber foliage long enough to be effective. The fecundity of C. sanguinea was the highest of those studied and a satisfactory laboratory rearing technique has been developed for this species.     

INSECTICIDAL CONTROL OF PAEDOGENETIC CECID LARVAE IN MUSHROOM BEDS

γ-BHC, incorporated at 50 p.p.m. in mushroom compost during the last turn of composting delayed the reproduction of paedogenetic cecid larvae without reducing the yield of mushrooms. Other insecticides were less satisfactory as they either did not control the larvae, were not sufficiently persistent or decreased the yield. Large cecid populations did not depress yields on normal composts but a proportion of the larvae migrated on to the sporophores, thus reducing the value of the crop.     

Multiscale topoedaphic heterogeneity increases resilience and resistance of a dominant grassland species to extreme drought and climate change

It is argued that the inclusion of spatially heterogeneous environments in biodiversity reserves will be an effective means of encouraging ecosystem resilience and plant community conservation under climate change. However, the resilience and resistance of plant populations to global change, the specific life‐history traits involved and the spatial scale at which environmentally driven demographic variation is expressed remains largely unknown for most plant groups. Here we address these questions by reporting an empirical investigation into the impacts of an unprecedented 3‐year drought on the demography, population growth rates (λ) and biogeographical distribution of core populations of the perennial grassland species Austrostipa aristiglumis in semiarid Australia. We use life‐history analysis and periodic matrix population models to specifically test the hypothesis that patch‐ and habitat‐scale variation in vital life‐history parameters result in spatial differences in the resilience and resistance of A. aristiglumis populations to extreme drought. We show that the development of critical soil water deficits during drought resulted in collapse of adult A. aristiglumis populations (λ?1), rapid interhabitat phytosociological change and overall contraction towards mesic refugia where populations were both more resistant and resilient to perturbation. Population models, combined with climatic niche analysis, suggest that, even in core areas, a significant reduction in size and habitat range of A. aristiglumis populations is likely under climate change expected this century. Remarkably, however, we show that even minor topographic variation (0.2–3 m) can generate significant variation in demographic parameters that confer population‐level resilience and resistance to drought. Our findings support the hypothesis that extreme climatic events have the capacity to induce rapid, landscape‐level shifts in core plant populations, but that the protection of topographically heterogeneous environments, even at small spatial scales, may play a key role in conserving biodiversity under climate change in the coming century.     

Identification of 13 polymorphic microsatellite loci in the zebra finch,Taeniopygia guttata (Passeridae,Aves)

Polymorphic microsatellite loci were identified in order to determine paternity in a captive population of the zebra finch, Taeniopygia guttata. Primer sets from 93 published passerine microsatellite sequences were tested for cross‐species amplification. Thirteen loci were found to be polymorphic, of which, eight displayed null alleles and one locus (Ase50) was found to be Z‐chromosome linked.     

In vitro Propagation of Narcissus

Adventitious shoots were induced on leaf, scale and stem explantstaken from the basal plate region of flowering-size bulbs onmedia containing 2–16 mg l^–1 6-benzylaminopurineand 0·25–4·0 mg 1^–1 1-naphthal-eneacetic acid (NAA). Only the levels of NAA had a significanteffect on the numbers of shoots produced. When trimmed and splitin half, 6 mm or more diameter in vitro shoots regenerated furtheradventitious shoots which in turn grew in size suitable forsplitting within 16 weeks. The vigour of the first generation of shoots was proportionalto the hormone levels used for their initiation. All shootseventually declined in vigour, senesced and formed dormant bulbils.Split senescent shoots regenerated only a few secondary shootswhich quickly became senescent. A total of 500–2000 bulbilscould be obtained from each initial bulb within 18 months. Bulbilsrequired 10 weeks at low temperature before planting to breakdormancy. Histological observations showed that in twin scales and splitshoots, adventitious shoots were regenerated from at least twosuperficial layers of menstematic cells near to the basal plate.This multicellular mode of origin suggests that plants multipliedfrom in vitro adventitious shoots could be as genetically uniformas those from natural vegetative increase. Narcissus, tissue culture, propagation, adventitious shoots, histology