C4 photosynthetic pathway and morphological functional types were determined for 104 species in 45 genera and 10 families from the deserts of China. 67 C4 species (64.4 %) were found in Dicotyledoneae (e.g. Chenopodiaceae, Polygonaceae, and Amaranthaceae), the other 37 species were in Monocotyledoneae (e.g. Gramineae, Cyperaceae, and Commelinaceae). 36.5 % of the Chenopodiaceae species (predominantly members of the genera Anabasis, Atriplex, Kochia, Salsola, and Suaeda) identified in the desert regions were found with C4 photosynthesis, which was about 48 % of the total C4 species. Many C4 species (58.7 %) were annuals (e.g. Amaranthus, Atriplex, Digitaria, Eragrostis, Kochia, and Salsola) and experienced long-term droughts, high temperature, and high irradiance. Relatively more shrub C4 species (28 species of 104) were found in Chenopodiaceae (e.g. Anabasis, Camphorosma, Haloxylon, and Salsola) and Polygonaceae (e.g. Calligonum) in the desert regions. Most of shrub C4 species with small leaf area were no more than 1 m in height and distributed in sandy soils. Composition of relatively more annual species, shrubs, and Chenopodiaceae C4 species was the primary characteristic for the C4 species occurrence in deserts, and this was remarkably related with the arid environmental conditions.
The differences in net photosynthetic rate (PN), transpiration rate (E), and water use efficiency (WUE) between the vegetative and reproductive shoots of three native grass species from the grassland of northeastern China [grey-green and yellow green populations of Leymus chinensis (Trin.) Tzvel., Puccinellia tenuiflora (Griseb) Scrib & Merr, Puccinellia chinampoensis Ohwi] were compared. The two type shoots experienced similar habitats, but differed in leaf life-span and leaf area. The leaf PN and WUE for the vegetative shoots were significantly higher than those for the reproductive shoots in the grasses, while their E were remarked lower in the dry season. Relative lower leaf PN and WUE for the reproductive shoots of grassland grasses may explain the facts of lower seed production and the subordinate role of seed in the grassland renewal in north-eastern China.
Photosynthetic pathway (C3, C4, and CAM) and morphological functional types were identified for the forage species from steppe vegetation in Inner Mongolia, China, using the data from both field survey and references. Of the total 136 identified vascular species, in 29 families and 89 genera, 78 % were found with C3 photosynthesis, including dominant herbs, e.g. Stipa grandis P. Smirn., S. krylovii Roshev., and Leymus chinensis (Trin.) Tzvel. These C3 species covered about 90 % of the total herbage production in the steppe. 20 % were found with C4 photosynthesis and 2 % with CAM photosynthesis. Photosynthetic pathway functional types were coarse and may not fit for the studies and land management in small scales, because of the high C3 photosynthesis composition and the few families in which C4 species occur. Morphological functional types (e.g. shrubs, high perennial grasses, short perennial graminaceous plants, annual grasses, annual forbs, perennial forbs, and succulents) may be practical for spatial and temporal descriptions of steppe ecosystems in local and region scales. Classification for plant functional types, especially morphological types, may contribute to studying the links between plant species and communities, ecosystems, and global changes, and for steppe management decisions in the region.
We examined the physiological and biochemical responses of two halophytic grasses with different photosynthetic pathways, Puccinellia tenuiflora (C3) and Chloris virgata (C4), to saline-alkaline stresses. Plants were grown at different Na2CO3 concentrations (from 0 to 200 mM). Low Na2CO3 (< 12.5 mM) enhanced seed germination and plant growth, whereas high Na2CO3 concentrations (> 100 mM) reduced seed germination by 45% in P. tenuiflora and by 30% in C. virgata. Compared to C. virgata, P. tenuiflora showed lower net photosynthesis, stomatal conductance, intercellular CO2 concentration, and water-use efficiency under the same treatment. C. virgata exhibited also relatively higher ATP content, K+ concentration, and the K+/Na+ ratio under the stress treatments implying that salt tolerance may be the main mechanism for salt resistance in this species. Our results demonstrated that the C. virgata was relatively more resistant to saline-alkaline stress than the co-occurring P. tenuiflora; both two species adapt to their native saline-alkaline habitat by different physiological mechanisms., C. Y. Guo, X. Z. Wang, L. Chen, L. N. Ma, R. Z. Wang., and Obsahuje bibliografii