[Show abstract][Hide abstract] ABSTRACT: Background and aims
Anthropogenic nitrogen (N) and phosphorus (P) input has changed the relative importance of nutrient elements. This study aimed to examine the effects of different nutrient conditions on the interaction between exotic and native plants.
We conducted a greenhouse experiment with a native species Quercus acutissima Carr. and an exotic species Rhus typhina L. grown in monocultures or mixtures, under three N:P ratios (5, 15 and 45 corresponding to N-limited, basic N and P supply and P-limited conditions, respectively). After 12 weeks of treatment, traits related to biomass allocation, leaf physiology and nutrient absorption were determined.
R. typhina was dominant under competition, with a high capacity for carbon assimilation and nutrient absorption, and the dominance was unaffected by increasing N:P ratios. R. typhina invested more photosynthate in leaves and more nutrients in the photosynthetic apparatus, enabling high biomass production. Q. acutissima invested more photosynthate in roots and more nutrients in leaf persistence at the expense of reduced carbon assimilation capacity.
Different trade-offs in biomass and nutrient allocation of the two species is an important reason for their distinct performances under competition and helps R. typhina to maintain dominance under different nutrient conditions.
[Show abstract][Hide abstract] ABSTRACT: Leaves are organs sensitive to environmental changes in the process of evolution and may exhibit phenotypic plasticity as a response to abiotic stress. However, affirmation of leaf morphological plasticity and its regulations in different environments are still unclear. We performed a simulated experiment to study the variations of leaf morphology in different gradients of water and light availability. Con-sidering different types of leaves and venation, we chose pinnate-veined simple leaves of Quercus acutissima and compound leaves of Robinia pseudoacacia as the study objects. The morphological parameters we investigated include leaf size, shape and venation pattern which can be easily measured in the field. Significant variations occurred in many parameters due to the effects of the environment and/or allometry. There were broadly consistent trends for leaf morphological variations along the gradients. The leaf size became smaller with a short supply of resources. Leaf elongation and fractions of the lamina area altered to enhance resources acquisition and conservation. Trade-offs between investments in support and functional structures optimized the venation pattern of major and minor veins. Leaflets partially played a role such as leaf teeth, for they are not only individual units, but also a part of the compound leaf. We suggest that more or less the same trends in morphological variations may be an important explanation for coexisting species to adapt to similar habitats and form the niche differentiation.
Full-text · Article · Dec 2009 · Progress in Natural Science
[Show abstract][Hide abstract] ABSTRACT: Leaf morphological, physiological and biochemical characteristics of Robinia pseudoacacia L. seedlings were studied under different stress conditions. The plants were subjected to drought and shade stress for one
month. Leaf inclination, chlorophyll fluorescence and chlorophyll content were measured at the first day (short-term stress)
and at the end of the stress period (long-term stress) and in the recovery period. Leaf inclination was affected mainly by
light; a low level of irradiance caused leaves to be arranged horizontally. Diurnal rhythmicity was lost after the long-term
stress, but resumed, in part, in the recovery period. Drought stress caused leaves to tilt more obviously and decreased damage
to the photosystem. Sun avoiding movement in a single leaf and sun tracking movement in the whole plant coexisted. Significant
physiological changes occurred under different conditions of light. Increased energy dissipation and light capture were the
main responses to high and low level of irradiance, respectively, and these were reflected by changes of chlorophyll fluorescence
and chlorophyll content. Phenotypic plasticity in the leaflet enhanced the protective response to stress. These adaptive mechanisms
may explain better survival of R. pseudoacacia seedlings in the understory, especially during the drought periods, and made it to be the preponderant reforestation species
in Shandong Province of China.
Full-text · Article · May 2009 · Acta Physiologiae Plantarum
[Show abstract][Hide abstract] ABSTRACT: This study surveyed and analyzed the vegetation heterogeneity in the Center of Inner Mongolia (CIM) by a new method based on the beta-binomial distribution for each kind of vegetation. As many as 190 large quadrats of 5mm×5mm (representing an area of 50km×50km) (referred to as L-quadrats hereafter) were extracted from about an area of 475,000km2. Each L-quadrat was divided into four small quadrats (S-quadrat) of 2.5mm×2.5mm (equivalent to 25km×25km) and the frequency of occurrence of each type of vegetation was recorded in each small quadrate. The weighted average heterogeneity from all of the vegetations composing a landscape provides a measure at landscape level to determine the spatial intricateness of landscape composition. Our results indicated that each vegetation has its own distribution pattern and the degree of heterogeneity is different from one kind of vegetation to the other. The results proved that the beta-binomial distribution can be very useful for analyzing vegetation landscapes.
Preview · Article · Mar 2008 · Progress in Natural Science
[Show abstract][Hide abstract] ABSTRACT: Phenotypic plasticity acts to Increase the performance of plants under stress. Leaf morphological plasticity and its causes in different environments are incompletely understood. We measured the leaf morphological parameters of Quercus acutissima Carr. seedlings, including leaf size, leaf shape and venation pattern, assessing the effects of different habitat conditions on leaf morphological plasticity. A field study in forest edge and understory was combined with experiments simulating different light and water conditions. Leaf morphology variations occurred over most of the parameters, and the causes were consistent between the field study and lab experiment. Leaf size decreased with low supply of light and water. Leaf length and width were only affected by leaf area. The leaf petiole did not lengthen under shade stress, suggesting a trade-off relationship between functional tissues and support structures. Leaf shape became narrower in drought and broader in the shade, as reflected in changes in three leaf fractions. Higher vein density played a part in enhancement of mechanical support and water supply. Leaves with more teeth show more active photosynthesis, but are disadvantageous in xeric environments because of higher transpiration. Light was the main factor inducing leaf morphological plasticity. The variations caused by drought were due mainly to the allometry. Our results showed that the leaves of Q. acutissima seedlings respond to different habitats with phenotypic plasticity of morphology, suggesting that this is an important mechanism for seedlings to adapt to broader ecological amplitudes.
No preview · Article · Jan 2008 · Acta biologica Cracoviensia. Series botanica