Involvement of Hormonal Balance in the Control of the 'Bullhead' Malformation in Baccara Rose Flowers

Gibberellin activity is much lower and cytokinin activity ishigher in the flowers of roses grown at a relatively low temperatureand in ‘pbullhead’ malformed flowers which appearin such conditions, compared to ‘normal’ flowersgrown at higher temperatures. Injection of gibberellin intothe receptacle of flowers grown at low temperature preventsthe symptoms of malformation. Injection with cytokinin of thoseflowers had no effect, but addition of BA¹ to GA injection abolishesthe malformation-preventing effect of the gibberellin. Cytokinintreatment of plants grown at higher temperatures causes proliferationof the nectary and promotes appearance of adventitious floretswhich are characteristic symptoms of malformed flowers. The level of auxin is higher in higher temperatures, but therewas no effect on the development of flowers at the various temperaturesby applying auxin. The involvement of hormonal balance in theabnormal development of rose flowers is discussed.     

Cytology of Encephalartos hildebrandtii A. Br. & Bouche

The chromosomes of Encephalartos hildebrandtii A. Br. &Bouche were studied from root tip cells (2n–27), and theplant was found to be a triploid on the basic chromosome number9. Karyotype analysis has shown that the somatic complementconsists of two sets of chromosomes, a diploid set of 18 chromosomesin nine paris, and a haploid set of 9, and therefore it is suggestedthat this is an allotriploid. This is the first report of a polyploid species in the genusEncephalartos, and also in the whole of the Cycadales.     

Changing land use reduces soil CH4 uptake by altering biomass and activity but not composition of high-affinity methanotrophs

Forest ecosystems assimilate more CO₂ from the atmosphere and store more carbon in woody biomass than most nonforest ecosystems, indicating strong potential for afforestation to serve as a carbon management tool. However, converting grasslands to forests could affect ecosystem–atmosphere exchanges of other greenhouse gases, such as nitrous oxide and methane (CH₄), effects that are rarely considered. Here, we show that afforestation on a well-aerated grassland in Siberia reduces soil CH₄ uptake by a factor of 3 after 35 years of tree growth. The decline in CH₄ oxidation was observed both in the field and in laboratory incubation studies under controlled environmental conditions, suggesting that not only physical but also biological factors are responsible for the observed effect. Using incubation experiments with ¹³CH₄ and tracking ¹³C incorporation into bacterial phospholipid fatty acid (PLFA), we found that, at low CH₄ concentrations, most of the ¹³C was incorporated into only two PLFAs, 18 : 1ω7 and 16 : 0. High CH₄ concentration increased total ¹³C incorporation and the number of PLFA peaks that became labeled, suggesting that the microbial assemblage oxidizing CH₄ shifts with ambient CH₄ concentration. Forests and grasslands exhibited similar labeling profiles for the high-affinity methanotrophs, suggesting that largely the same general groups of methanotrophs were active in both ecosystems. Both PLFA concentration and labeling patterns indicate a threefold decline in the biomass of active methanotrophs due to afforestation, but little change in the methanotroph community. Because the grassland consumed CH₄ at a rate five times higher than forest soils under laboratory conditions, we concluded that not only biomass but also cell-specific activity was higher in grassland than in afforested plots. While the decline in biomass of active methanotrophs can be explained by site preparation (plowing), inorganic N (especially NH₄⁺) could be responsible for the change in cell-specific activity. Overall, the negative effect of afforestation of upland grassland on soil CH₄ uptake can be largely explained by the reduction in biomass and to a lesser extent by reduced cell-specific activity of CH₄-oxidizing bacteria.