Radioisotopic Method for Measuring Cell Division Rates of Individual Species of Diatoms from Natural Populations †

Populus euphratica Oliv. and Tamarix ramosissima Ledeb. are the dominant riparian plants in desert ecosystems in China, where they play a significant role in maintaining ecological balance. To obtain a better insight into the ecological adaptations of xylem structure and hydraulic traits in desert phreatophytes to extremely drought-stressed environments, we investigated various quantitative features of the vessels and intervessel pits, as well as the xylem hydraulic efficiency (Ks(max)) and native embolism rate (PLC, %), in the woody shoots and lateral roots (all c. 2–4.5 mm in diameter) of P. euphratica and T. ramosissima from natural populations in the Heihe River Basin, northwestern China. The relationships between xylem anatomy and hydraulic traits are also discussed. There were significant anatomical differences between lateral root and woody shoot xylem within individual species. For lateral roots , arithmetic, hydraulic and maximum vessel diameter (D, Dh, Dmax), average vessel area (Va), intervessel wall thickness (Tvw), intervessel pit membrane and pit aperture areas (APM, APA), and intervessel pit membrane and pit aperture diameters (DPM, DPA), were larger than in woody shoots (P < 0.05).The mean Ks(max) values in lateral roots were 6–11 times greater than in woody shoots for P. euphratica and T. ramosissima, respectively (P < 0.01). Woody shoots of T. ramosissima had higher native PLC values (68%) than P. euphratica (39%).The different vessel grouping patterns in the two species seemed to be related to their different native embolism level. It is possible that the lateral roots of these two riparian desert plants could be more resistant to embolism than the woody shoots, and that cavitation resistance in the root xylem of T. ramosissima is higher than that of P. euphratica.

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Theory of Growth and Competition in Natural Populations

Journal of the Fisheries Research Board of Canada ◽

10.1139/f53-016 ◽

1953 ◽

Vol 10 (5) ◽

pp. 211-223 ◽

Cited By ~ 7

Author(s):

Gordon A. Riley

Keyword(s):

Theoretical Analysis ◽

Population Growth ◽

Food Chain ◽

Feeding Habits ◽

Natural Populations ◽

Individual Species ◽

Ecological Groups ◽

Reproductive Patterns ◽

Complete Form

Classical theories of population growth and inter-species relations are briefly reviewed. It is shown how variations in feeding habits, reproductive patterns, and other aspects of population behaviour have required modifications of the basic theory in order to make it applicable to particular species. The role of the environment in population theory is also discussed, and this opens the way to a consideration of theoretical aspects of the ecology of natural populations. The latter are admittedly too complex to encourage the application of theory in its purest and most complete form. Practical attempts along these lines have simplified the problem by dealing with ecological groups—phytoplankton, zooplankton, etc.—rather than individual species. A review is presented of the methods, aims, and results of theoretical ecological investigations of the last few years. The significance of such work with respect to higher members of the food chain is discussed, and the paper concludes with remarks on some of the unsolved problems of theoretical analysis.

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Rapid Accumulation of Mutations in Growing Mycelia of a Hypervariable Fungus Schizophyllum commune

Molecular Biology and Evolution ◽

10.1093/molbev/msaa083 ◽

2020 ◽

Vol 37 (8) ◽

pp. 2279-2286

Author(s):

Aleksandra V Bezmenova ◽

Elena A Zvyagina ◽

Anna V Fedotova ◽

Artem S Kasianov ◽

Tatiana V Neretina ◽

...

Keyword(s):

Cell Division ◽

Mutation Rate ◽

De Novo ◽

Schizophyllum Commune ◽

Natural Populations ◽

De Novo Mutations ◽

Rapid Accumulation ◽

Living Organisms ◽

Very High ◽

Rate Of Accumulation

Abstract The basidiomycete Schizophyllum commune has the highest level of genetic polymorphism known among living organisms. In a previous study, it was also found to have a moderately high per-generation mutation rate of 2×10−8, likely contributing to its high polymorphism. However, this rate has been measured only in an experiment on Petri dishes, and it is unclear how it translates to natural populations. Here, we used an experimental design that measures the rate of accumulation of de novo mutations in a linearly growing mycelium. We show that S. commune accumulates mutations at a rate of 1.24×10−7 substitutions per nucleotide per meter of growth, or ∼2.04×10−11 per nucleotide per cell division. In contrast to what has been observed in a number of species with extensive vegetative growth, this rate does not decline in the course of propagation of a mycelium. As a result, even a moderate per-cell-division mutation rate in S. commune can translate into a very high per-generation mutation rate when the number of cell divisions between consecutive meiosis is large.

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