Changes in dormancy and viability of Amaranthus retro¯exus seeds were examined after placement in pots that were buried in the ®eld. Seeds were placed in woven nylon envelopes on the soil surface or buried at depths of 2.5, 5 or 10 cm. After 1, 3, 6, 9 and 12 months seeds were exhumed and their germinability was tested to assess changes in dormancy and viability. Depletion of seed stocks placed on the soil surface was partly because of in situ germination that did not exceed 21% and did not vary signi®cantly over the 12-month study period. Less germination of buried seeds occurred in situ, and seeds that did not germinate appeared to acquire dormancy. Exhumed seeds germinated readily; germinability was linearly related to the depth of burial, with those retrieved from the surface germinating least. Cyclical changes in germinability occurred during the 12-month burial period, but this in¯uence was identical for seeds buried at all depths. Germinability was greatest after periods with the lowest mean monthly temperatures and least during the hottest periods. The stimulation of remaining ungerminated seeds exhumed at each period, by the addition of ethephon to the germination medium, provided further evidence of a seasonal acquisition of dormancy, and it was concluded that other unknown factors besides cyclical changes in seasonal temperature were responsible. Irrespective of placement, all seeds lost viability at an exponential rate over time. However, the decline was most rapid for those placed on the surface, whereas the loss in viability became less with increased depth of burial. Possible explanations for this adaptation of enhanced survival when buried are discussed.

In this paper we demonstrate the ability of the Taguchi technique accurately to characterize and successfully to optimize complicated multi-response processes with the minimum of experiments, provided one uses simple statistical techniques which can ensure valid, and definitive results. We point out the usefulness of suitable data-transformations, and we suggest a systematic procedure for establishing the optimal operating conditions and for carrying out confirmatory experiments.For the particular case detailed in this paper (which is typical of multi-response processes) the Taguchi technique achieved an improvement in uniformity of a factor of 2, together with optimized process control.

Data from twenty experiments, conducted at ADAS Research Centres in England and Wales during 1986–92, were used to determine effluent production from additive‐treated grass silages made in large‐scale bunker silos. The additives compared were formic acid at 4·0  l t–1, rolled barley at 44·0 kg t–1, dried molassed sugar beet feed at 40·0 kg t–1 and liquid inoculants at 2·2 l t–1 together with a non‐additive‐treated control. The silages were made from herbage with an average dry‐matter (DM) content of 177 (s.e. 3·8) g kg–1 and water‐soluble carbohydrate content of 140 g kg–1 DM. Average silage toluene DM content was 213 (s.e. 3·8) g kg–1. The formic acid and sugar beet feed silages were both well fermented, whereas the other silages were less well fermented. Effluent produced was determined as either effluent production (l t–1 grass ensiled) during the 52‐d period in which it was measured or peak flow (l h–1) during the first 2 d of ensilage. Compared with non‐additive‐treated silage, dried molassed sugar beet feed significantly reduced both effluent production (27%) and peak flow (36%). Formic acid significantly increased peak flow (51%), but had little effect upon effluent production, and significantly reduced effluent N and lactic acid content. Barley and inoculant treatment had no significant effect upon effluent production. In general, poor relationships were found between DM content and effluent production. Nevertheless for silages, except those treated with absorbents or formic acid, a significant (P < 0·001) negative relationship between silage effluent production (l t–1 grass ensiled) and the DM (g kg–1) content of the ensiled grass was found.

Changes in soluble sugars in cauliflower seeds were followed during 50 h of imbibition in relation to desiccation tolerance Sucrose and stachyose contents decreased, and glucose and fructose accumulated This occurred in radicles first and subsequently in hypocotyls and cotyledons Loss of desiccation tolerance in the various seed parts coincided with an increase in glucose and fructose and the complete loss of stachyose, but sucrose content, the major sugar, was still high Drying imbibed seeds over silica gel did not evoke resynthesis of stachyose, but did increase sucrose and decrease glucose and fructose contents Seeds primed in solutions of 30% polyethylene glycol for 10 days showed a loss of stachyose, while sucrose remained high and glucose and fructose contents were still very low Redrying of primed seeds did not change the sugar contents The primed seeds were still tolerant of desiccation We conclude that stachyose is not a prerequisite for desiccation tolerance, but that sucrose may be We suggest that glucose and fructose may be involved in desiccation damage

Compared to tree responses to elevated (e)CO2, little attention has been paid to understorey plant community responses in forest ecosystem studies, despite their critical role in nutrient cycling and the regeneration of overstorey species. Here, we present data on understorey responses from a 3‐year Free‐Air CO2 Enrichment experiment in a native, phosphorus‐limited Eucalyptus woodland in Australia (EucFACE). We conducted repeat surveys of the understorey plant community from 2012 to 2016, recording cover at the species level. Three years of eCO2 significantly decreased the diversity (Shannon‐Weaver; −30%) and species richness (−15%; c. −1 species per 4 m2 plot) of graminoid species, and the cover of C4 graminoids in both dominant (−38%) and subordinate (−48%) groups, relative to ambient conditions, leading to a significantly lower graminoid C4:C3 ratio (−59%) in the understorey plant community. The ratio of C4:C3 graminoids was negatively associated with soil nitrogen (N) availability suggesting that previously reported eCO2‐associated increases in N availability may contribute to (or be a consequence of) shifts in the composition of the graminoid community at the study site. There was, however, no effect of eCO2 on the diversity of forb species, which represented the most species‐rich functional group but only c. 1% of the understorey biomass. Synthesis. Our results suggest that eCO2 influences competition between C4 and C3 graminoid species both directly and indirectly via increasing N availability. The shift towards lower C4:C3 ratios and enhanced dominance by C3 species with their generally higher tissue N concentrations could further change soil nutrient availability and potentially accelerate community succession. Thus, eCO2 has altered the diversity and composition of the understorey plant community in this woodland, with the potential for cascading consequences for trophic interactions and ecosystem function.

In 2010, an online survey was conducted to assess the current status of the Australian stingless bee industry and its recent development. This was a follow-up survey conducted approximately one decade after the first study, by Heard and Dollin in 1998/99. It showed that the Australian industry had grown over the past ten or so years but is still underdeveloped. There was a 2.5-fold increase in the number of bee keepers and a 3.5 fold increase in the number of domesticated colonies. Seventy-eight percent of bee keepers were hobbyists, 54% of whom owned only one colony. Most colonies were kept in suburban areas. Two species, Tetragonula carbonaria and Austroplebeia australis, dominated the relatively short list of species kept. There was a high demand for Australian stingless bee colonies and their honey, but with less than 250 bee keepers currently propagating colonies, and many of them on a small scale, it is difficult to meet this demand. Pollination services were provided by less than 4% of the major stakeholders within the industry. Further research and development in the area of colony propagation may see this industry grow more quickly. La industria australiana de la abeja sin aguijón: un estudio de seguimiento, una década después ResumenEn 2010, se realizó una encuesta en línea para evaluar el estado actual de la industria australiana de la abeja sin aguijón y su evolución reciente.Este estudio de seguimiento fue llevado a cabo aproximadamente una década después del primer estudio realizado por Heard y Dollin en 1998/99. Se demostró que la industria australiana ha crecido en los últimos diez años, pero sigue estando subdesarrollada. Ha habido un aumento de 2,5 veces en el número de los apicultores y un aumento de 3,5 veces en el número de colonias domesticadas. El setenta y ocho por ciento de los apicultores fueron aficionados, de los cuales el 54% tenían sólo una colonia. La mayoría de las colonias se mantuvieron en áreas suburbanas.Dos especies, Tetragonula carbonaria y Austroplebeia australis, dominaron la relativamente corta lista de especies mantenidas. Hubo una gran demanda de colonias de abejas sin aguijón de Australia y de su miel, pero con menos de 250 apicultores distribuyendo colonias actualmente, y muchos de ellos en una escala pequeña, es difícil satisfacer esta demanda. Los servicios de polinización fueron proporcionados por menos del 4% de los factores principales dentro de la industria. Más investigación y desarrollo en el área de propagación de colonias podrían hacer que esta industria creciera más rápidamente.

Water uptake during the germination of UC 82B tomato seeds was triphasic. Seed Ψ measurements indicated that phase I imbibition occurred because of the large Ψ gradient between the seed and the imbibition solution (water). During phase II the seed Ψ was in equilibrium with the water. Phase III water uptake recommenced with the onset of radicle emergence without changes in Ψ or Ψπ. Changes in embryo water content were also triphasic. During phase II the embryo Ψ remained at - 1.5 MPa, not in equilibrium with the imbibing solution. At radicle emergence it was - 0.8 MPa and rose to -0.3 MPa as the radicle elongated. There was no evidence of a lowering of embryo Ψπ nor of a build up of Ψp prior to radicle emergence. Water uptake studies with excised embryos indicated that, within the seed, the enclosing tissues prevented the embryo from taking up water. It is suggested that embryo water content is restricted by the constraint on embryo expansion caused by the enclosing endosperm tissue. Lowering of embryo Ψπ to build up Ψp is not necessary for radicle emergence. The control of germination may lie in the mechanism which leads to weakening of this mechanical restraint of the endosperm.

No abstract