Publications (2)0 Total impact
-
Article: Interactive effects of salinity, light, and temperature on seed germination of Zygophyllum simplex L. (Zygophyllaceae) in Jordan
[show abstract] [hide abstract]
ABSTRACT: A number of abiotic factors are known to affect seed germination and distribution patterns of plants in natural habitats. In this study, the interactive effects of temperature, light/darkness and different salts of different concentrations on seed germination of the Jordanian succulent herb Zygophyllum simplex were investigated. Seeds showed 60% germination percentage in non-saline controls at 25ºC. Cooler temperatures diminished germination to less than 10% at 5ºC. Seed germination of Z. simplex was significantly affected by salt type, concentration, temperature and their interactions. Similar germination percentage was found for seeds incubated under light or dark conditions. Z. simplex germinated best at intermediate temperature regime (15 and 25ºC), and at this temperature, salinity co-acts and affects seed germination. Results of this study indicate that the interactive effect between temperature and salinity could be an adaptive strategy that allows Z. simplex to survive and reproduce in harsh desert habitats of Jordan.International Journal of Integrative Biology. 01/2010; -
Article: Leaf anatomy, gas exchange and photosynthetic enzyme activity in< i> Flaveria kochiana
[show abstract] [hide abstract]
ABSTRACT: Flaveria (Asteraceae) is one of the few genera known to contain both C 3 and C 4 species, in addition to numerous biochemically-intermediate species. C 3 -C 4 and C 4 -like intermediate photosynthesis have arisen more than once in different phylogenetic clades of Flaveria. Here, we characterise for the first time the photosynthetic pathway of the recently described species Flaveria kochiana B.L. Turner. We examined leaf anatomy, activity and localisation of key photosynthetic enzymes, and gas exchange characteristics and compared these trait values with those from related C 4 and C 4 -like Flaveria species. F. kochiana has Kranz anatomy that is typical of other C 4 Flaveria species. As in the other C 4 lineages within the Flaveria genus, the primary decarboxylating enzyme is NADP-malic enzyme. Immunolocalisation of the major C 4 cycle enzymes, PEP carboxylase and pyruvate, orthophosphate dikinase, were restricted to the mesophyll, while Rubisco was largely localised to the bundle sheath. Gas exchange analysis demonstrated that F. kochiana operates a fully functional C 4 pathway with little sensitivity to ambient oxygen levels. The CO 2 compensation point (2.2 µbar) was typical for C 4 species, and the O 2 -response of the CO 2 compensation point was the same as the C 4 species F. trinervia. Notably, F. vaginata (B.L. Robinson & Greenman), a putative C 4 -like species that is the nearest relative of F. kochiana, had an identical response of the CO 2 compensation point to O 2 . Furthermore, F. vaginata, exhibited a carbon isotope ratio (−15.4‰) similar to C 4 species including F. australasica Hooker, F. trinervia Spreng. C. Mohr and the newly characterised F. kochiana. F. vaginata could be considered a C 4 species, but additional studies are necessary to confirm this hypothesis. In addition, our results show that F. kochiana uses an efficient C 4 cycle, with the highest initial slope of the A/C i curve of any C 4 Flaveria species. Additional keywords: C 4 photosynthesis, C 3 -C 4 photosynthesis, C 4 evolution, CO 2 compensation point, Kranz anatomy.
