Abstract:To understand the activities of nitrogenase and N₂O reductase (Nos) for non-legume nitrogen-fixing tree species, the detached nodules, rhizospheric soil in nodule root grown area (RSI) and rhizospheric soil near nodule root grown area (RSN) were collected from Casuarina cunninghamiana and Alnus trabeculosa in Fujian Province, southeastern China, and the nitrogenase and Nos activities were determined by acetylene reduction method and acetylene inhibition technique, respectively. The results showed that the nitrogenase activity of detached nodules could be detected only under anaerobic condition, and the Nos activity only in aerobic condition. The nitrogenase activity in RSI and RSN under aerobic conditions was higher than those under anaerobic condition, and the Nos activities could be detected only under anaerobic condition. In aerobic condition, there was no significant difference in nitrogenase activity between RSI and RSN, while Nos activity of RSI was significantly larger than that of RSN. The nitrogenase activity were greater than Nos activity for the two tree species, except that there were no nitrogenase activity for the detached nodules under aerobic condition. The nitrogenase activity in the RSI under aerobic condition was significantly positively correlated with that in RSN. However, the nitrogenase activity in nodules under anaerobic condition was negatively correlated with that in RSI and RSN under aerobic condition, and the Nos activity in nodules under aerobic condition was also negatively correlated with that in RSI and RSN under anaerobic condition. These would lay a foundation for studying the effect and regulation of symbiotic nitrogen fixation system of tree species nodulated with Frankia on N₂O sink intensity.

Abstract:In order to understand the adaptive mechanism of Rhododendron latoucheae community in Jinggang Mountain, Jiangxi Province, the changes in leaf functional traits of dominant species in shrub layer were analyzed along altitude. The results showed that the altitudinal gradient had significant effects on leaf functional traits of shrub species. The dry matter content (LDMC), thickness (LT), nitrogen (LNC) and phosphorus concentration (LPC) of leaves increased with altitude rising, whereas the specific leaf area (SLA) and N/P reduced, and the leaf size (LS) increased at first and then decreased. There were significant relations among leaf functional traits. LDMC had negative relation with SLA and LS, positive relation with LT, LNC and LPC. SLA and LT, LNC and LPC had positive relation, whereas LS and LT, N/P and LPC had negative relations, respectively. Environment factors influence on leaf functional traits. Except for altitude, slope also affected SLA, LPC and N/P, and aspect and gradient influenced LS and LNC, respectively. So, it was suggested that the shrub species in Rhododendron latoucheae community could adapt altitude and other environment factors by adjusting leaf functional traits.

Abstract:To explore the effect of Si nutrition on cold resistance of red sandalwood (Pterocarpus santalinus), one-year-old seedlings applied silicon (Si) for 180 d were suffered (-3±0.5)℃ stress for 24 h, and then recovered for 90 d in greenhouse, the growth status, leaf photosynthetic parameters and activities of four key enzymes related carbon assimilation of the seedlings were studied. The results showed that the seedlings applied Si were strong, growth recovery was fast after cold stress, the cold resistance was significantly improved. After applied Si, the decreases of chlorophyll content and Chl a/b of seedlings caused by cold stress were significantly inhibited, the apparent electron transfer rate (ETR), actual photon efficiency Y(Ⅱ) and PSⅡ regulatory energy dissipation Y(NPQ), and reduced the proportion of PSⅡ non-regulated energy dissipation Y(NO) and non-photochemical quenching (NPQ) were all promoted, and the leaf photosynthetic rate (Pn), stomatal conductance (Gs) and water use efficiency (WUE) of red sandalwood seedlings under cold stress increased after applied Si. The activities of four key enzymes related carbon assimilation, such as ribulose-1,5-bisphosphate carboxylase (Rubisco), fructose- 1,6-phosphatase (FBP), fructose-1,6-bisphosphate aldolase (Ald) and phosphoenolpyruvate carboxylase (PEPC), of seedlings applied Si were significantly higher than those of non-applied Si. Therefore, application of the appropriate amount of Si benefits the integrity of photosynthetic membrane structure and stability of physiological functions of seedlings under cold stress, and it is an effective nutrient management measure improving the cold resistance and coping with cold stress of red sandalwood seedlings.

Abstract:In order to select salt-tolerance germplasms of rice (Oryza sativa) germplasms, the physiological indexes related salt tolerance were studied under salt stress. The results showed that the salt tolerance germplasms, such as Pokkali, Fl478 and JX99, had low conductivity, small cell membrane permeability, and high chlorophyll content in leaf, showing weak salt damage. The malondialdehyde content, the degree of cell membrane lipid peroxidation increased under salt stress. The malondialdehyde accumulated in salt-tolerant germplasm less than that in sensitive germplasm, but the malondialdehyde content in three salt-tolerant germplasms also increased under high salt stress, which destroyed the integrity of cell membrane. The critical saturation deficit in sensitive germplasm R29 greatly enhanced, while the relative water content in salt-tolerant germplasms slightly decreased. So, the order of salt tolerance was JX99 > Pokkali > FL478 > IR29 by fuzzy membership function method.

Abstract:In order to understand the stress resistance characters of Canavalia maritima in Paracel Islands, the anatomical structure, physiological characteristics and nutrient status of leaves were studied. The results showed that palisade tissue of C. maritima leaves developed well with high density of stomata. The chlorophyll a/b was lower than 3:1. The antioxidants enzyme activities were high, especially the activity of SOD was the highest, and content of proline was high. In addition, under low soil nutrient content, the nutrient content in leaves was high. Therefore, Canavalia maritima could be used for vegetation restoration and reversing desertification, because it had characters in resistance to drought, strong light, high temperature and infertile.

Abstract:To clarify the physiological and biochemical mechanism of 5-aminolevulinic acid (ALA), the alleviating effect of ALA on Camptotheca acuminata seedlings under salt stress were studied. The results showed that the alleviating effect on C. acuminata seedlings under salt stress was the best treated with 80 mg L^-1 ALA. Treated with 80 mg L^-1 ALA spraying leaves of C. acuminata under salt stress, the antioxidant capacity was enhanced, the nitrogen and chlorophyll contents increased significantly, the damage of PS Ⅱ under salt stress was relieved, which Fv/Fm was 24.35% higher than that of control, and carbon-assimilation capacity increased, Pn was 45.38% higher than that of control, so that the growth of seedlings under salt stress was promoted. The peroxidase (POD) activity and chlorophyll content of C. acuminata seedlings did not increase with increment of ALA concentration. Therefore, these would provide the theoretical basis for salt cultivation of C. acuminata.

Abstract:In order to make protection strategies of rare and endangered plants in Lushan National Nature Reserve, the endangered grade and conservation priority of 58 rare and endangered species were evaluated with indexes, such as endangered coefficient, genetic coefficient and species value coefficient. The results showed that the comprehensive evaluation value (VS) of rare and endangered plants in Lushan Nature Reserve ranged from 0.153 to 0.742. There were 11 species with safe grade, accounting for 19% of the total of rare and endangered plants in this area; 28 species fall into rare species for 48%; 18 species for 31% were listed in vulnerable species; and the endangered species had 1 species for 2%. Among those, 8 species were assessed as the first conservation class, accounting for 14% of the total of rare and endangered species, and 22, 23 and 5 species belong to the second, the third and the fourth conservation class, accounting for 38%, 40% and 8%, respectively, there were not rare and endangered species. So, it was concluded that the habitat destruction and human disturbance were the main threats to rare and endangered plants of the region.

Abstract:To understand the embryological characteristics of Dodonaea viscosa in the dry and hot valley and the reasons for its low seed setting rate, microsporogenesis, male gametophyte development and pollen morphological characteristics of D. viscosa were studied with traditional paraffin sections and scanning electron microscopy. The results showed that the anther of D. viscosa had four pollen sac. The anther wall was composed of the epidermis, the endothecium, 2-3 middle layers, and tapetum (glandular tapetum) from the outside to the inside; at anther mature stage, the middle layer and tapetum denegerated and disappeared. The cytokinesis occurred simultaneously in a microspore mother cell; the tetrad was tetrahedral. The mature pollen was two-celled type. The mature pollen grain was nearly spherical with granular ornamentation on exine and 3 germ furrows which did not form syncolpate. Our researches showed that some abnormal phenomenon in male reproductive development might be one of the reasons of low seed setting rate.

Abstract:In order to understand the effect of host diversity and functional traits on host specificity of mistletoe, the mistletoe and host species as well as the degree of host specificity of mistletoe in Xishuangbanna Tropical Botanical Garden were investigated. The results showed that there were 1 323 host individuals, belonging to 58 families 190 genera and 286 species, infected by 6 mistletoe species and 1 variety, belonging to 2 families 5 genera. There was significant difference (P<0.01) in infection density among different habitats, which was the highest in monoculture plantation, and the lowest in forest. The degree of host specificity (H') of seven mistletoe species ranged from 1.92 to 7.05. According to redundancy analysis, the DBH, bark water content and bark roughness of host species were significantly correlated with the distribution of mistletoe on host species, whereas wood density and bark pH had not significant correlation. In conclusion, mistletoe species showed great difference in host specificity in tropical plant community, which could partly explained by the preference on specific host functional traits of mistletoe species.

Abstract:To understand the chemical constituents of Chinese agarwood "Qi-Nan", seven compounds were isolated by various column chromatographic methods. On the basis of spectral data, they were identified as cis-7-hydroxycalamenene (1), (5R,6R,7S,8R)-2-(phenylethyl)-6,7,8-trihydroxy-5,6,7,8-tetrahydro-5-[2-(2-phenylethyl) chromonyl-6-oxy]chromone (2), 1-hydroxy-1,5-diphenylpentan-3-one (3), syringaresinol-glycoside (4), (3β)- olean-12-ene-3,23-diol (5), β-sitosterol (6) and hexadecanoic acid, 2,3-dihydroxypropyl ester (7). Compounds 1, 3-5, and 7 were isolated from agarwood for the first time, and compound 1 showed a very sweet aromatic odor. Compound 1 showed acetylcholinesterase (AChE) inhibitory activity with the inhibition rate of (49.9±1.4)% at the concentration of 50 μmol L^-1.

Abstract:In order to understand the chemical constituents of Ardisia gigantifolia, the gigantifolinol were isolated and identified from EtOAc extract. In vitro activity screening, gigantifolinol showed potent anti-inflammatory and anti-tumor activities, and moderate neuroprotection activities. This is the first systematic study of gigantifolinol, which might provide a scientific basis to the development and utilization of A. gigantifolia.

Abstract:In order to study the chemical constituents from Pseuderanthemum latifolium and their biological activities, two main compounds were isolated from the EaOAc fraction and identified as lupeol (1) and stigmasterol (2) by using LC-MS guided isolation. In vitro activity screening, all these compounds showed moderate anti-MRSA activities but no neuroprotective effects. This is the first report about the chemical constituents from P. latifolium and their biological activities, which would provide scientific basis to the development and utilization of P. latifolium.

Abstract:To clarify the chemical constituents in the leaves of Dalbergia odorifera T. Chen (Leguminosae), eight non-flavonoid compounds were isolated from the ethanol extract and decoction of the leaves by means of chromatographic separation techniques. Based on spectral data, their structures were identified as (3S)-6,7- dihydroxy-6,7-dihydrolinalool (1), icariside B1 (2), icariside B6 (3), icariside F2 (4), benzyl alcohol β-vicianoside (5), phenethyl alcohol β-vicianoside (6), butane-2,3-diol 2-O-β-D-glucoside (7), and adenine (8). Compound 1 is a monoterpene, compounds 2 and 3 are megastigmane glucosides, compounds 4-6 are aryl glycosides, compound 7 is an alkyl glucoside, and compound 8 is a purine. All the compounds were reported from this species for the first time.

Abstract:In order to understand the chemical constituents of artificially induced dragon's blood of Dracaena cambodiana, ten compounds were isolated from the ethanol extract. On the basis of spectral data, their structures were indentified as socotrin-4'-ol (1), homoisosocotrin-4'-ol (2), (E)-3-(3,4-dihydroxybenzylidene)-7-hydroxy- chroman-4-one (3), 5-hydroxy-7-methoxy-3-(4'-hydroxybenzyl)-4-chromanone (4), 3-deoxysappa­nchalcone (5), sappanchalcone (6), 7,4'-dihydroxyflavone (7), 7,4'-dihydroxy-8-methylflavone (8), syringares­inol (9) and bis (2-ethylhexyl) phthalate (10). All compounds were isolated from artificially induced dragon's blood of Dracaena cambodiana for the first time, compound 8 was a new natural product, compounds 3-6 were isolated from dragon's blood for the first time. The compounds 7 and 8 had inhibitory activities against methicillin-resistant Staphylococcus aureus (MRSA).

Abstract:PPR proteins are one of the largest protein families in terrestrial plants, both on category and volume. The main functions of PPRs were involved in post-transcriptional modifications and editing of specific single-stranded RNAs in the nucleus and organelles via their localization in various organelles. PPRs play important roles in series events of plant growth and development. Mutants of most PPR protein-encoding genes exhibit abnormal developmental phenotypes, such as embryonic lethality, developmental retardation, and greening delays. The recent research advances of PPRs in classification, localization, RNA modification mechanisms and their functions on regulating growth and development of plants were summarized, and the studies on functional area and participating regulatory network of PPR in plants was prospected.