In the past two decades, the field of study of mating system and dispersal processes in plants has greatly expanded. Attention has particularly focused on the use of maternal progeny arrays to estimate short-term rates of outcrossing and selfing frequencies, and to examine patterns of pollen dispersal and male fertility variation within populations. Earlier studies relied on exclusion methods but realized that many gene flow events were not being detected by these techniques and that unique parentage could not be determined for a large proportion of the non-immigrant offspring in most natural populations. Consequently, methods for maximum-likelihood estimation of gene flow and male fertility have been introduced. Estimations of relative frequencies of outcrossing and selfing in populations and families based on single-locus and multi-locus models are discussed in this paper. Attention is given to the method of parentage analysis and the estimation of the level of gene flow. As an example, we present our studies of mating system and paternity analysis on Ophiopogon xylorrhizus, an endangered plant in China.

Mating system is an important factor affecting the genetic structure of plant populations. Determining mating system can aid in the understanding of reproductive patterns of plants, and help predict the trend of genetic structure of plant populations following environmental change, such as habitat fragmentation. Ardisia crenata var. bicolor, a hermaphrodite species, is an understory shrub of evergreen broad-leaved forests in East China. Three polymorphic loci (Adh-1, Fe-2 and Amp-2) were analyzed to determine the mating systems of two A. crenata var. bicolor populations. Multiple loci outcrossing rates of the two populations were 1.055 and 1.159, respectively. This may represent a combination of several small groups into large populations as a small number of families in groups can not be used to calculate the multilocus outcrossing rate. Low outcrossing rates were found in families of small groups but not in those of large groups, indicating that outcrossing rate will be reduced with small population size or low density of flowering plants. We discuss the effects of fragmentation of evergreen broad-leaved forests on the mating system of A. crenata var. bicolor populations.

The variation in ring growth indices of Picea meyeri was assessed by dendrochronological techniques including response functions, correlation functions and single-year analysis on sandy dunes in the Xilin River basin steppe. The results show that growth of Picea meyeri was sensitive to climate change. Furthermore, it was determined that mean monthly temperature and total monthly precipitation from September of the current year to August of the preceding year can account for about 70% of the variance in the tree-ring width. The rainfalls in February and May of the current year together with that of the previous September were significantly correlated with the current year’s growth pattern. Additionally ,radial growth was negatively correlated with mean monthly temperature in current May. In this region the sandy substrate is characterized by high water infiltration and low soil moisture evaporation rates. As a result, relatively high precipitation from prior August to prior October can be reserved in the sandy soil and the Picea meyeri trees show strong adaptation to the sandy substrate in these se- mi-arid grasslands. Therefore, the establishment of Picea meyeri forest plantations in the sandy belt along the middle reaches of Xilin River are deemed feasible.

A better understanding of the effect of temperature and moisture on soil nitrogen mineralization is important to aid our ability to predict soil N cycling. The objective of this study was to evaluate the effects of temperature (T) and soil water content (θ) on nitrogen mineralization in a deciduous broad-leaved forest. Extracted soil cores were kept in a PVC tube adjusted to different soil water contents (0.12 kg·kg-1, 0.2 kg·kg-1, 0.28 kg·kg-1, 0.35 kg·kg-1 and 0.4 kg·kg-1) and incubated at 5℃, 15℃, 25℃ and 35℃ for 30 days. The inorganic N in the soil extracts before and after incubation was analyzed. The results showed that soil nitrogen net mineralization and net nitrification rates were positively related to T and θ effects (p<0. 001) from 5℃ to 25℃. And that there was a decrease in net mineralization rate and nitrification rate when the temperature was raised above 25℃ and water content was more than 0.20 kg·kg-1. These results suggest an interactive effect of temperature and moisture on mineralization rate and nitrification rate. Two dimensional (T, θ) equations were developed to describe these effects.

The dry-season dynamics of soil inorganic nitrogen pools were investigated under three types of vegetation (Primary Lithocarpus xylocarpus forest, secondary oak forest and tea plantation), which represent three different intensities of disturbance. Pools of inorganic nitrogen in soils (0-15 cm) showed strong differences between the three types of vegetation. Organic material, total nitrogen reduced and C/N ratio fell with increasing intensity of disturbance, while nitrate loss potential rose. These results suggest that disturbance does not favor the retention of soil nutrient elements. The dry-season dynamics of the inorganic nitrogen pools were similar under the three vegetation types while the dynamics of NH+-N differed from that of NO3--N’s. NH4+-N was the major form of inorganic nitrogen, and NO3-N content only was 1.16%-3.44%, 0.58%-2.09% and 2.02%- 7.37% of NH4+-N content in the primary Lithocatpus xylocarpus forests, secondary oak forests and tea plantations.

Gravitation soil solutions were investigated by using flat lysimeters in a nudal beech forest (group of types of geobiocens Fageta paupera typica inferiora, type of geobiocen Carex pilosa nudum), located in the Ecological Experimental Station (EES) Kremnicke vrchy mountains (Central Slovakia). Chemical properties of the percolated soil solutions were sampled monthly below surface humus (Ao-horizon) and the 10 cm and 25 cm thick mineral layers of andosolic cambisol. The soils were sampled monthy in Ao horizon, 10 cm and 25 cm depth, and their contents of four chemical elements Ca,Mg,K and Na, and pH and conductivity were analysed. The following amounts of the basic cations have been accumulated in mineral soil layers during the year (the balance is negatively influenced by freezing of Ao lysimeter in the winter) :calcium 2.6 kg Ca2+·hm-2 and 14.2 kg Ca2+·hm-2,magnesium 2.1 kg Mg2+·hm-2 and 1.1 kg Mg2+·hm-2,potassium 42.1 kg K+·hm-2 and 2.3 kg K+·hm-2,sodium 5.5 kg Na+·hm-2 and 2.0 kg Na+·hm-2.

In this study, young pepper (Capsicum annuum L. cv. Xiang-Yanl0) leaves were used to examine the effects of exogenous Ca2+ pretreatment on electrolyte leakage, ascorbate(AsA) and glutathione(GSH) contents, and the change in Ca2+ distribution in mesophyll cells under heat stress. The results show that exogenous Ca2+ pretreatment can alleviate the damage of cell membrane caused by heat stress. The amount of GSH and AsA in calcium-treated leaves under heat stress was higher than that in control leaves. In the control pepper seedlings growing under normal temperature, deposits of calcium antimonate, an indicator for Ca2+ localization, were observed within the vacuoles, intercellular spaces, and chloroplasts. This indicates that Ca2+ pretreatment could induce changes in Ca2+ distribution and significantly increase the Ca2+ level in intercellular spaces, vacuoles and chloroplasts. When calcium-treated leaves were under heat stress at 40˚, the amount of Ca2+ located in intercellular space decreased, and most of them transferred to cytosol and chloroplast across the plasmalemma. The results suggest that exogenous Ca2+ results in changes in Ca2+ distribution between inter-and intracellular spaces and, as a result, the ultrastructure of mesophyll cells could be protected from damage caused by heat stress.

The quality of Bruguiera gymnorrhiza and Rhizophora stylosa hypocotyl budding and rooting in water of different salinities (expressed relative to normal sea water) was studied in seeds from the Guangxi coast. Seawater salinity lower than 10‰ promoted the budding and rooting of B. gymnorrhiza hypocotyls. Relative to those grown in water with salinity levels higher than 20‰ and 30‰ these began rooting about 6 days earlier and mean rooting was 7.1-4.8 days earlier. Rooting rates were 20%-30%. The best seawater salinity condition for R. stylosa hypocotyl rooting was about 20‰ at which the rooting rate and mean rooting rate were 90% and 68% respectively. The rooting rate was only 40% in freshwater. A novel bimodal phenomenon in the continuous rooting rate of B. gymnorrhiza hypocotyles was also observed. Budding of R. stylosa hypocotyls appears to be limited when their base is exposed to light.

Artemisia sphaerocephala Krasch. is a dominant shrub in large areas of active and stabilized sandy deserts of northwest China. The seeds of A. sphaerocephala are light sensitive, germinating in light but poorly in dark. The optimal temperature for germination is 25℃. At 10℃ and 30℃ germination velocity was slow and reached low total percentages, at 5℃ germination was inhibited. The deeper the seeds were placed in sand, the lower and slower was their germination. No seedlings emerged from achenes located at 2 cm or more cm. However, when the upper layer of sand was removed leaving deep buried seeds at under just 0.5 cm of sand, their germination reached the same percentages as the seeds located 0.5 cm deep from the beginning of wetting, but at a faster rate. With higher sand moisture content, from 1.7% to 14.7% water content, germination was earlier. From 19.4 % soil moisture germination was delayed and seedlings remained undeveloped.