In vitro shoot regeneration from leaf explants of Echinops kebericho: an endangered endemic medicinal plant

Echinops kebericho is a critically endangered endemic medicinal plant of Ethiopia. It is threatened due to over harvesting of its roots for medicinal purposes and from poor seed viability. This study aimed to develop a protocol for in vitro shoot regeneration from leaf explants of E. kebericho. The seeds were sterilized using ethanol followed by Clorox or calcium hypochlorite. Shoots from the germinated seeds were cultured on Murashige and Skoog (MS) medium containing different concentrations of α-naphthalene acetic acid (NAA) and 6-benzyl amino purine (BAP). Young leaves were cultured on MS medium containing different concentrations of BAP and NAA for shoot regeneration. For shoot multiplication, shoots were excised and cultured on MS medium containing different concentrations of BAP or kinetin (KIN) and NAA. The highest mean number of initiated shoots (4.00 ± 0.57) with 100% shoot induction was obtained on medium containing 1.0 mg/L BAP and 0.2 mg/L NAA. The highest shoot regeneration (33%) and shoot number (2.13 ± 0.06) were obtained on MS medium containing 2.0 mg/L BAP and 0.5 mg/L NAA. Medium containing 1.0 mg/L KIN and 0.2 mg/L NAA produced the highest number of shoots (4.67 ± 0.33) per explant. This protocol can be used for genetic improvement and conservation of this endangered species.     

Decadal Trends and Common Dynamics of the Bio-Optical and Thermal Characteristics of the African Great Lakes

The Great Lakes of East Africa are among the world’s most important freshwater ecosystems. Despite their importance in providing vital resources and ecosystem services, the impact of regional and global environmental drivers on this lacustrine system remains only partially understood. We make a systematic comparison of the dynamics of the bio-optical and thermal properties of thirteen of the largest African lakes between 2002 and 2011. Lake surface temperatures had a positive trend in all Great Lakes outside the latitude of 0° to 8° south, while the dynamics of those lakes within this latitude range were highly sensitive to global inter-annual climate drivers (i.e. El Niño Southern Oscillation). Lake surface temperature dynamics in nearly all lakes were found to be sensitive to the latitudinal position of the Inter Tropical Convergence Zone. Phytoplankton dynamics varied considerably between lakes, with increasing and decreasing trends. Intra-lake differences in both surface temperature and phytoplankton dynamics occurred for many of the larger lakes. This inter-comparison of bio-optical and thermal dynamics provides new insights into the response of these ecosystems to global and regional drivers.     

Nitrogen fixation and assimilation efficiency in Ethiopian and German pea varieties

Dinitrogen (N₂) fixation and assimilation efficiency in a German and two Ethiopian varieties of Pisum sativum L. was studied in a pot experiment during vegetative and reproductive growth. The objective of the study was to assess whether genotypes having contrasting growth habits showed differences in physiological processes that affect the efficiency of N₂ fixation and assimilation. Dry matter formation, nodulation and nitrogen assimilation were compared between two treatments where one depended solely on N₂ fixation while the other was nourished with nitrate. Moreover, carbon (C) costs of N₂ fixation and the capacity of different respiratory chains in roots and nodules were determined at vegetative and reproductive growth. As compared to the Ethiopian cultivars, the German variety displayed a more rapid vegetative growth with intensive N₂ fixation and assimilation and highly efficient individual nodules. However, during reproductive growth, N₂ fixation in the German variety declined sharply, while continuing in the Ethiopian varieties. Lowest C costs of N₂ fixation coincided with most efficient individual nodules in both growth intervals. C costs of N₂ fixation were lower during reproductive growth in all varieties which was accompanied by a shift in root/nodule respiratory capacity towards more C efficient respiratory pathways. The results provide further evidence that unreliable nitrogen fixation rates during reproductive growth of pea can be connected with restricted C supply to nodules. One strategy of pea plants to adapt to critical C availability is an increase in capacity of more C efficient root/nodule respiration.