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Ulmus elongata is on the verge of extinction due to habitat fragmentation and habitat loss. Identifying the environmental factors affecting the leaf traits of U. elongata is important for understanding its endangerment mechanisms. Specific leaf area (SLA), leaf nitrogen content, and leaf carbon isotope discrimination (δ13C) were determined. Temperature and light were found to be the main environmental factors influencing SLA, indicating that U. elongata is heliophilous. The maximum and minimum δ13C values of the plant species were − 26.33‰ and − 29.64‰, respectively (the mean was − 28.09‰), suggesting that it is of the C3 photosynthetic type. Compared with the altitude, annual sunshine duration, annual precipitation, and mean annual temperature accounted for 36% of the variance in δ13C, which is the main environmental factor affecting 13C fractionation. The foliar δ13C value of U. elongata was significantly more negative than that of Ulmus pumila, a widely distributed elm tree in northern China (P

Magnolia cylindrica Wils. is one of the third most-protected wild plants in China. To describe the size structure and dynamics of its population, field data were obtained from eight newly established sites, using a contiguous grid quadrate method in Jiulong Mountain of East China. The population size structure and spatial distribution pattern were discussed based on a theoretical distribution model and assembling intensity index. The population size structure showed a declining trend because of the lack of seedlings. The number of stump-sprouting, size class III (sapling trees) individuals was large enough to make up for the shortage of small seedlings and the complete regeneration of populations through sprouting. The distributions of M. cylindrica, both seedling populations (Group A) and overall populations (Group B), were mostly clumped. The spatial pattern intensities of the populations at different stages (mainly small trees, middle trees, and big trees) were higher for Group A than those for Group B. The two groups have the same tendency in that the pattern intensity declined from small trees to the larger ones. Group A and Group B differed in spatial pattern: small and middle trees were randomly distributed in seedling populations, but aggregated in overall populations. The populations of M. cylindrica (both group A and B) were characterized by the pattern scale between 16 to 32 m2, measured by Greig-Smith and Kershaw methods. These results suggest that sprouting should be seriously considered in population rehabilitation and forest tending management and the area of forest tending management should be close to the maximum intensity.

Toxicity of Fe2+ is one of the major constraints for lowland rice production in tropical and subtropical areas. The root tip is a primary site of iron (Fe2+) toxicity in rice. To explore the effects of iron toxicity on the morphological and biological characteristics on the border cells in rice (Oryza sativa L.), experiments were carried out using the border cells in two cultivars. The experimental results revealed the following properties of border cells shared by both rice cultivars: the first border cells appeared almost synchronously with the emergence of the primary root tip; the number of border cells reached maximum when the root was 25 mm long; the border cells were most viable when the root length was 20 mm; and the relative activity of pectin methylesterase (PME) was the highest when the root length was 2 mm. The two rice cultivars exhibited different trends in their response to Fe2+ toxicity: the number of root border cells in Fe2+-resistant Zhongyou 9288 increased when experiencing low...

Hydroponic experiments were performed to investigate the effects of exogenous organic acids on Al accumulation and Al forms in two rape genotypes, Heza No. 7 (Al-tolerant) and Zhongnongyou No. 6 (Al-sensitive) under Al stress. Results showed there exhibited diverse effects on different varieties of rape. Citrate can significantly improve the absorption of Al in Heza No. 7. Al content in Al + citrate increased by 50 % compared with single-Al treatment. In Zhongnongyou No. 6, the highest Al content was observed under mixed treatment with citrate and malate. Organic acids significantly promoted the absorption of Mg, Ca, K, and Fe in roots of Zhongnongyou No. 6, but there were fewer effects on elemental absorption by Heza No. 7. Al-NMR results showed that Al in rape root mainly existed in the form [AlO4Al12(OH)24(H2O)12]7+, with a chemical shift of about 63 ppm. Upon addition of exogenous organic acids, Al mainly existed as non-phytotoxic forms of Al–citrate and Al–malate complexes and showed fewer Al–F complex, Al(OH) 2 4+ , and Al(OH) 2 4+ species. This finding can explain why rape root accumulates large amounts of Al upon treatment with exogenous organic acids but shows no serious toxicity symptoms. We thus conclude that Al–citrate and Al–malate play important roles during Al detoxification in rape.

The physiological and ecological responses of Ulmus elongata to different concentrations of nano-anatase TiO2 solutions were investigated in this study and we found that with foliar application of 0.1% (T1), 0.2% (T2) and 0.4% (T3) nano-anatase TiO2 solution the net photosynthetic rate of U. elongata seedlings were lower, comparing with the control (CK) (no spraying). TiO2 solution had no effect on the carbon isotope values (δ(13)C), indicating the lower photosynthetic capacity was not caused by stomatal limitation. The nitrogen isotope values (δ(15)N) decreased, but the foliar metal elements, such as Mg, K and Mn contents were not affected by nano-anatase TiO2 which promoted the Cu uptake. Fourier transform infrared spectroscopy showed that the nano-anatase TiO2 enhanced the absorbance of U. elongata leaves, especially for 1064, 1638, 2926 and 3386 cm(-1) bands, indicating the synthesis of carbohydrate and lipid compounds was a kind of mechanism under the toxic effects of nanonanoparticles.

Root border cells are a population of rhizosphere cells surrounding the root tips but separated from them. The root tip is a major target of Fe2+ toxicity; thus, it was hypothesized that the border cells might protect or exacerbate Fe2+ toxicity. To explore the effects of excess Fe2+ on the border cells in rice (Oryza sativa L.), experiments were carried out using the border cells in vitro (Shanyou No. 10). The border cells were precultured under “hanging in the air” and detached from the root tips. The shape, numbers, and viability of border cells were examined during exposure to toxic levels of Fe2+. When the root was 1 mm long, there were 205 border cells on average. With the growth of the root, more border cells were observed. When the root grew to 25 mm long, the total number of border cells reached a maximum, while the maximum activity of border cells appeared when the root was 20 mm long. The pectin methyl esterase (PME) activity of the root cap peaked at a root length of 2 mm. Border cell development was related to PME activity in rice. Excessive Fe2+ was toxic to detached border cells. After treatment with 200 μM Fe2+ solution for 48 h, cell viability decreased by 72.70%. However, when treated with 400 μM Fe2+ solution, the number of viable cells was actually higher, suggesting the induction of a cellular self-protection response. The activity of PME first increased under high concentrations of Fe2+ and then decreased. These results indicate that toxic levels of Fe2+ modulate PME activity and border cell survival.

The phylogenetic relationship between Ulmus elongata trees growing in different geographic regions was studied by Fourier transform-infrared spectroscopy (FTIR), thermogravimetric analysis, and differential thermal technology. We found that the infrared absorbance values of FTIR spectra differed significantly between U. elongata samples from seven distributed regions. We defined four genetic groups (clades) of U. elongata by differences in 16 characteristic absorbance peaks. The trees (named by regions) were sorted as follows: Shexian Anhui (AHSX) and Lin’an Zhejiang (ZJLA) in clade I, Kaihua (ZJKH), Suichang Zhejiang (ZJSC), and Wuning Jiangxi (JXWN) in (clade II); Songyang Zhejiang (ZJSY) in clade III, and Nanping Fujian (FJNP) clade IV. Thermogravimetric and differential thermal analysis revealed that the leaves of U. elongata had two obvious exothermic pyrolysis stages, and reached maximum mass loss near 550 °C. TG and DT curves between 350 and 550 °C were also used to elucidate the phylogenic relationship between U. elongata samples.

This study used hydroponics cultivation to investigate the manganese (Mn) accumulation and tolerance abilities of six species—Phytolacca americana L., Poa annua L., Comnyza canadensis L., Cynodon dactylon L., Polygonum hydropiper L., and Polygonum perfoliatum L. We found that P. perfoliatum, P. hydropiper, and P. americana were Mn-hyperaccumulators and that P. perforliatum have superior Mn accumulation and toleration abilities over the other five species. The Mn concentration within the shoots of P. perfoliatum reached as high as 18,342.3 mg kg−1. The root growth of P. perfoliatum was promoted under low-Mn treatments, but the growths of the five other species were inhibited by the Mn treatments and the damage intensified as Mn concentration increased. The biomass of P. perfoliatum was minimally affected by the Mn treatments. The chlorophyll (CHL), soluble protein (SP), and malondialdehyde (MDA) contents of P. perfoliatum were not adversely affected, but these parameters of the other five species showed significant (P

Different plants have physiological responses under Al stress, but there is no systematic study to examine physiological responses of herbaceous plants under Al stress. The aim of this study is to investigate the effect of Al on physiological characteristics of four herbaceous plants, which distributed in red soil area in South China, and to analyze the differences in physiological responses to Al stress between the four herbaceous plants. Four herbaceous plants (Pharbitis nil, Cassia occidentlis, Echinochloa colonum and Aeschynomene indica) were used, and the seed germination percentage, the contents of chlorophyll, proline, and malondialdehyde (MDA), membrane permeability (MP), soluble sugar, and activities of peroxides (POD) and catalase (CAT) in leaves under five Al3+ treatments (0, 80, 400, 2 000, and 10 000 mg/L) were assayed with the sand culture method. The results showed remarkable effects of Al3+ on physiological characteristics of these four herbaceous plants. The seeds of all the four species could not germinate at 10 000 mg/L, and the growth of all plants were retarded under the 2 000 mg/L Al3+ treatment. Compared with the control, 2 000 mg/L Al3+ significantly (P < 0.05) reduced the contents of chlorophyll a and chlorophyll a + b, and increased the contents of MDA and MP. The content of proline increased very significantly (P < 0.01) and activities of POD and CAT were depressed. The contents of MDA and MP in leaves of P. nil and A. indica decreased, and the activities of POD and CAT in leaves of the two plants increased under 80 mg/L and 400 mg/L. However, the changes in C. occidentlis leaves were opposite to those of the above two plants. The changes in leaves of E. colonum were similar to those of P. nil and A. indica at 80 mg/L, but were opposite to those at 400 mg/L Al3+. It is suggested that plants with higher activities of POD and CAT, more contents of chlorophyll and proline, and lower contents of MDA and MP consequently improve the tolerance to Al stress under low and middle Al treatments.

Seven-son flower ( Heptacodium miconioide ) is a prized, useful and well-accepted landscape plant in North America and some European countries but only grows in East China. Unfortunately, the distribution region, population size and individual numbers of seven-son flower rapidly decrease in the wild. It is a particular rare, highly severe endangered and protective plant. Here we investigated the physiological responses of seven-son flower at eight different sites under fragmental habitats in the Beishan mountains (Zhejiang, China), one of two only areas where the communities of seven-son flower currently are discovered. This was to determine the effect of light stress under fragmental habitat on the physiology and to explore the endangering mechanism of seven-son flower. The study shows that strong light brought by habitat fragmentation obviously inhibited the photosynthesis rates reduced antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX)) activities and promoted electrical conductivity and MDA content of seven-son flower leaves. The characteristics of leaves were also affected by light intensity in fragmental habitat. Intense light in fragmental habitat is disadvantageous to photosynthesis and antioxidant enzymes of the flower. Our results suggest that biodiversity conservation of seven-son flower is timely needed and the light intensity should be considered carefully when biodiversity conservation of seven-son flower to be carried out, especially in the transplant conservation of seven-son flower from deteriorative area in the wild.

The physiological and ecological responses of Ulmus elongata to different concentrations of nano-anatase TiO2 solutions were investigated in this study and we found that with foliar application of 0.1% (T1), 0.2% (T2) and 0.4% (T3) nano-anatase TiO2 solution the net photosynthetic rate of U. elongata seedlings were lower, comparing with the control (CK) (no spraying). TiO2 solution had no effect on the carbon isotope values (δ(13)C), indicating the lower photosynthetic capacity was not caused by stomatal limitation. The nitrogen isotope values (δ(15)N) decreased, but the foliar metal elements, such as Mg, K and Mn contents were not affected by nano-anatase TiO2 which promoted the Cu uptake. Fourier transform infrared spectroscopy showed that the nano-anatase TiO2 enhanced the absorbance of U. elongata leaves, especially for 1064, 1638, 2926 and 3386 cm(-1) bands, indicating the synthesis of carbohydrate and lipid compounds was a kind of mechanism under the toxic effects of nanonanoparticles.