A nursery experiment was conducted to determine the effects of seed pretreatment methods on the germination of Faidherbia albida at ICRAF, Nairobi from six provenances consisting of Awassa, Taveta, Lake Koka, Maseno, Chinzombo and Wagingombe. Seeds were subjected to five pretreatment methods namely nicking, soaking in acid, hot water, cold water and control. Germination percentages (GP), mean germination time (MGT) and germination index (GI) were calculated and the data was subjected to ANOVA. The study revealed significant (p B 0.05) differences in seed treatments among provenances in all studied parameters. Highest germination among pretreatments in Awassa (99 %) and Wagingombe (80 %) was observed in nicked seeds, Chinzombo (81 %) in nicked and acid treated seeds, Lake Koka (90 %) in acid treated seeds and Taveta (28 %) and Maseno (64 %) in cold water treated seeds. Nicking gave the highest cumulative GP (69.67) while lowest GP was observed in hot water treated seeds (23.17). Acid treatment exhibited lowest MGT (8.85 days) and highest GI (2.29) while highest MGT (24.35 days) and lowest GI (0.31) were observed in control and hot water treatment respectively. Although acid treatment gave a high GP and lowest MGT and GI, nicking and soaking in cold water for 24 h is being recommended as cheaper and less hazardous pretreatment methods to improve germination in F. albida since sulphuric acid is expensive and requires proper handling techniques. Significant correlation between geo-climatic data and germination parameters of seeds subjected to different pretreatments indicates that provenances are as important as pretreatments in germination of the species.

No abstract

Main conclusion Enhanced levels of indole-3-acetic and raised auxin to cytokinin ratios in the stem base contribute to the positive acropetal gradient in rooting capacity of leafy single-node stem cuttings of rose. Abstract Cuttings excised from different nodal positions in stock plants can differ in subsequent adventitious root formation. We investigated the involvement of the auxin–cytokinin balance in position-affected rooting of Rosa hybrida. Leafy single-node stem cuttings of two rose cultivars were excised from top versus bottom positions. Concentrations of IAA and cytokinins were monitored in the bud region and the stem base during 8 days after planting using chromatography–MS/MS technology. The effects of nodal position and external supply of indole-butyric acid on rooting were analyzed. Most cytokinins increased particularly in the bud region and peaked at day two before the bud break was recorded. IAA increased in both tissues between day one and day eight. Top versus bottom cuttings revealed higher levels of isopentenyladenosine (IPR) in both tissues as well as higher concentrations of IAA and a higher ratio of IAA to cytokinins particularly in the stem base. The dynamic of hormones and correlation analysis indicated that the higher IPR contributed to the enhanced IAA in the bud region which served as auxin source for the auxin homeostasis in the stem base, where IAA determined the auxin–cytokinin balance. Bottom versus top cuttings produced lower numbers and lengths of roots, whereas this deficit was counterbalanced by auxin application. Further considering other studies of rose, it is concluded that cytokinin-, sucrose- and zinc-dependent auxin biosynthesis in the outgrowing buds is an important factor that contributes to the enhanced IAA levels and auxin/cytokinin ratios in the stem base of apical cuttings, promoting root induction.

In vitro techniques have been shown to be useful in identifying relatively drought-tolerant genotypes at early stages of development. In this study, drought-induced alterations in early shoot and root development of 59 sweetpotato genotypes was evaluated in the tissue culture laboratory at the Kenya Plant Health Inspectorate Services, Quarantine station, Muguga, Kenya. These genotypes were obtained from Lima, Peru and were evaluated against two known Kenyan check varieties, Marooko (drought tolerant) and K566632 (drought susceptible). Plantlets of each genotype were raised on Murashige and Skoog basal solid medium, from an original node consisting of a 0.2-0.5 cm stem segment. These were exposed to polyethylene glycol (PEG 6000) at three different concentration levels: 0, 10 and 15 g/l. The experiment was laid out in a factorial completely randomized design with three replications. Data on shoot and root growth were recorded during tissue regeneration lasting over a period of 4 weeks per regeneration cycle. Analysis of variance indicated genotypes, salt levels and salt level × genotype interaction, were highly significant (P<0.01) with respect to all the traits. At 15 g/l concentration of PEG, genotypes 189135.9, 194515.5, 440024, 441724 and 440001 had roots that were longer than those of Marooko. Genotypes 194515.5, 194539.36, 441724, 441538, 189135.9, 41768, 192033.5 and 440429 recorded greater leaf expansion, greater stem length elongation, greater root and shoot growth and high dry matter production at all salt levels indicating their ability to withstand severe water stress conditions. Genotypes 189151.38, 420027, 440132, 440104, 440034, 421111, 440166 and 441755 were identified as susceptible. The technique was found to be a useful tool for screening a large number of sweetpotato genotypes within a relatively short period of time.

(2013) Avian foraging behaviour in relation to provision of ecosystem services in a highland East African agroecosystem, Bird Study, 60:2, 156-168,