Root-Derived Short-Chain Suberin Diacids from Rice and Rape Seed in a Paddy Soil under Rice Cultivar Treatments

Suberin-derived substituted fatty acids have been shown to be potential biomarkers for plant-derived carbon (C) in soils across ecosystems. Analyzing root derived suberin compounds bound in soil could help to understand the root input into a soil organic carbon pool. In this study, bound lipids were extracted and identified in root and topsoil samples. Short-chain suberin diacids were quantified under rice (Oryza sativa L.) and rape (Brassica campestris) rotations with different cultivar combinations in a Chinese rice paddy. After removal of free lipids with sequential extraction, the residual bound lipids were obtained with saponification and derivatization before analysis using gas chromatography–mass spectrometry (GC-MS). Diacids C16 and C18 in bound lipids were detected both in rice and rape root samples, while diacids C20 and C22 were detected only in rape root samples. Accordingly, diacids were quantified in both rhizosphere and bulk soil (0–15 cm). The amount of total root-derived diacids in bulk soil varied in a range of 5.6–9.6 mg/kg across growth stages and crop seasons. After one year-round rice-rape rotation, root-derived suberin diacids were maintained at a level of 7–9 mg/kg in bulk soil; this was higher under a super rice cultivar LY than under a hybrid cultivar IIY. While concentrations of the analyzed diacids were generally higher in rhizosphere than in bulk soil, the total diacid (DA) concentration was higher at the time of rape harvest than at rice harvest, suggesting that rape roots made a major contribution to the preservation of diacids in the paddy. Moreover, the net change in the concentration and the ratios of C_16:0 DA to C_18:1 DA, and of C_16:0 DA to C_18:0 DA, over a whole growing season, were greater under LY than under IIY, though there was no difference between cultivars within a single growth stage. Overall, total concentration of root-derived suberin diacids was found to be positively correlated to soil organic carbon concentration both for bulk soil and rhizosphere. However, the turnover and preservation of the root suberin biomolecules with soil property and field conditions deserve further field studies.     

Defoliation and its Effects on Pod and Seed Development in Oil Seed Rape (Brassica napus L.)

Both in vivo and in vitro techniques have been used to followthe development of individual pods on the terminal inflorescenceof undefoliated and defoliated plants of oil-seed rape (Brassicanapus cv. Maris Haplona). For any pod, a rapid increase in podlength occurred between 2 d and 8 d after flower opening andthis preceded by approximately 2 d the increase in pod width,the rate of which was less than that for length. An increasein the diameter of individual seeds coincided with the increasein pod width. Regional increases in the length and width ofpods were associated with the presence of developing seeds inthese regions. Key words: Brassica napus L., Development, In vivo, Pod and seed, Stress     

大豆异黄酮对干旱胁迫下油菜幼苗生长的影响

研究在模拟干旱的条件下喷施大豆异黄酮对油菜(Brassica campestris)幼苗抗旱性的影响.结果表明:0.1 mg/L的大豆异黄酮处理过的油菜幼苗,叶绿素a含量是对照的1.69倍、硝酸还原酶和过氧化物酶活性分别比对照增强了52.85%和30.73%、类黄酮含量比对照增加了49.1%、丙二醛含量比对照降低了26.61%、根系活力比对照高出近1倍.上述结果表明低浓度的大豆异黄酮能明显减轻干旱胁迫对油菜幼苗生长的伤害作用.     

Effects of Chemical Treatments upon Photosynthetic Parameters in Soybean Seedlings

The effects of various chemical treatments upon photosynthesis, soluble leaf protein, CO₂ compensation point, and leaf light transmission in soybean, Glycine max (L.) Merr., seedlings were examined following varying response periods after application at 14 to 17 days postemergence. The compounds N⁶-benzyladenine (BA), 2-(4-chlorophenoxy)-2-methylpropanoic acid (CPMP), (4-chlorophenoxy)acetic acid (CPA), rhodanine-N-acetic acid (RAA), and 2,3,5-triiodobenzoic acid (TIBA) significantly increased soluble protein and decreased senescence, measured by leaf light transmission, at CO₂ concentrations below the compensation point in a survival chamber. All compounds except BA significantly decreased transmission values under ambient atmospheric conditions. In statistically significant experiments, applications of 3.49 millimolar CPMP increased net photosynthesis on a leaf area basis by an average of 14.4% at all trifoliolate positions with increases generally requiring response periods of 12 days or longer. RAA at 1.31 and 2.61 millimolar increased net photosynthesis by 19 to 36% following 13-day response periods. CPMP and other compounds tested had no effect upon the CO₂ compensation point after 4- to 8-day response periods. The effects of CPMP and RAA upon net photosynthesis and soluble protein appeared to involve a combined stimulation of protein synthesis and an antisenescent effect. There were no indications that any of the photosynthetic changes observed resulted from direct differential effects upon ribulose bisphosphate carboxylase-oxygenase. The assays for soluble protein and light transmission responded more consistently to the chemicals than did photosynthesis.     

Ovule Fertilization and Seed Number per Pod Determination in Oil Seed Rape (Brassica napus)

Ovule fertilization in relation to seed number determinationin spring rapeseed, Brassica napus var. Maris Haplana, was investigated.Failure of fertilization was found to be the major factor limitingthe number of seeds per pod in both the basally and apicallylocated pods on the terminal inflorescence. Sufficient pollengermination on a stigma did not guarantee full seed set andeven when pollen tubes were present at the micropyle regions,ovules were not penetrated. Some seeds aborted: in some, triplefusion did not take place while other seeds were small and deemedat disadvantage to compete for available nutrients. Brassica napus, fertilization, ovules, seeds     

Isolation and Identification of Three Potassium-Solubilizing Bacteria from Rape Rhizospheric Soil and Their Effects on Ryegrass

More than 90% of potassium (K) in soil exists in forms of insoluble silicate minerals and cannot be directly utilized by plants. K-solubilizing bacteria (KSB) can improve soil fertility and plant growth as biofertilizers by decomposing silicate minerals and releasing insoluble K into soluble forms. The objectives of this study were to isolate and characterize KSB from rape rhizospheric soil and to evaluate their effects on ryegrass growth. In this study, 16 cultivable potential KSB were isolated from rape rhizosphere at first. Then, quantitative analysis revealed that three KSB strains, named S-15, S-17 and S-18, showed the best K mineral solubilizing ability and they were identified as Mesorhizobium sp., Paenibacillus sp. and Arthrobacter sp. Inoculating the three strains into available K limit soil increased available K content significantly. The result of the pot experiment revealed that the three strains increased ryegrass growth vigor, biomass yield and K uptake to different degrees in available K deficient soil. S-17 showed the most pronounced ryegrass growth promotion ability. Further studies are required to determine the effects of the three KSB on mobilization of K-bearing minerals under field conditions.     

Nematicide Treatments of Turfgrass Seed

Seed treatments of improved Kentucky bluegrass and fescue cultivars with carbofuran, oxamyl, and phenamiphos dissolved in acetone reduced seedling emergence, but treatments were not extremely phytotoxic. Phenamiphos was the most toxic, particularly at the 5,000 μg/ml concentration. Fresh weight of grass clippings 35 d following planting generally was greater in treatments than in controls except for the 5,000 μg/ml phenamiphos treatments on certain cultivars. All nematicide seed treatments reduced the number of Pratylenchus penetrans subsequently recovered from Pennlawn creeping red fescue roots 4-5 wk after treatment. The infusion of nematicides into grass seed with organic solvents appears to be an effective means of reducing nematode damage to turfgrass seedling with little environmental hazard.     

Effects of Volatiles Evolved from Excised Plant Tissues and Lemon Oil on the Growth of Mung Bean Seedlings

Volatiles evolved from excised segments of leaves of oleander(Nerium oleander) and cedar (Cedrus deodara), peels of lemon(Citrus limon), orange (Citrus sinensis) and lime (Citrus aurantifolia),and roots of wasabi (Wasabia japonica) inhibited growth of mungbean seedlings. The volatiles evolved from lemon oil also markedlyinhibited elongation of mung bean seedlings. The active constituent(s)in the volatiles were distinct from ethylene. The mode of inhibitionby the volatiles from lemon oil was different from that of ethylene.The volatiles from lemon oil alleviated the inhibitory effectof ethylene on the growth of seedlings. The volatiles from lemonoil supressed the formation of lamellar structure in chloroplasts,thus resulting in etiolation of seedlings. (Received October 25, 1982; Accepted December 29, 1982)     

连栽土壤对杉木幼苗生长影响的研究

连栽土壤对杉木幼苗生长影响的研究马越强廖利平杨跃军汪思龙高洪陈楚莹（中国科学院沈阳应用生态研究所,１１００１５）刘更有（湖南省会同县林科所,４１８３０７）ＥｆｅｃｔｓｏｆＲｅｐｌａｎｔＳｏｉｌｏｎｔｈｅＧｒｏｗｔｈｏｆＣ．ｌａｎｃｅｏｌａｔａＳｅｄｌ...     

Emergence Shapes the Structure of the Seed Microbiota

Seeds carry complex microbial communities, which may exert beneficial or deleterious effects on plant growth and plant health. To date, the composition of microbial communities associated with seeds has been explored mainly through culture-based diversity studies and therefore remains largely unknown. In this work, we analyzed the structures of the seed microbiotas of different plants from the family Brassicaceae and their dynamics during germination and emergence through sequencing of three molecular markers: the ITS1 region of the fungal internal transcribed spacer, the V4 region of 16S rRNA gene, and a species-specific bacterial marker based on a fragment of gyrB. Sequence analyses revealed important variations in microbial community composition between seed samples. Moreover, we found that emergence strongly influences the structure of the microbiota, with a marked reduction of bacterial and fungal diversity. This shift in the microbial community composition is mostly due to an increase in the relative abundance of some bacterial and fungal taxa possessing fast-growing abilities. Altogether, our results provide an estimation of the role of the seed as a source of inoculum for the seedling, which is crucial for practical applications in developing new strategies of inoculation for disease prevention.     

若干种子处理方法对偃松种子生活力的影响

为了提高偃松种子生活力,采用水浸、NaOH溶液浸泡、PEG6000（PEG,聚乙二醇）溶液浸泡、低温冷冻、吸湿/回干5种方法对偃松种子进行处理,研究不同处理中各因素（如溶液浓度、处理时间与温度）对偃松种子生活力的影响,并采用靛蓝染色法测定偃松种子的生活力。结果表明：10%PEG6000溶液、初始温度60℃、浸泡36 h时,偃松种子生活力最强;水浸、低温处理和吸湿/回干处理方法也能提高偃松种子生活力;然而4%~12%NaOH溶液浸泡处理会导致偃松种子生活力下降。因此可将PEG6000溶液处理种子的方法应用于偃松种子萌发及人工种苗培育的实践中,使偃松资源得到更好的可持续开发与利用。     

野生蜂窝草籽中挥发油的研究

采用水蒸气蒸馏法从野生蜂窝草籽中提取挥发油,利用气相色谱-质谱联用技术对其挥发油中的化学组分进行分离和结构鉴定,运用气相色谱面积归一化法确定各个组分的相对百分含量。从蜂窝草籽挥发油中鉴出56种成分,主要组分是油酸(12.57%),棕榈酸(10.36%),1-辛烯-3-醇(7.96%),石竹烯(5.98%),2,4,6-三甲基-1,3,6-庚三烯(5.63%)等。对蜂窝草籽挥发油进行了抗氧化实验和抗菌实验,结果表明蜂窝草籽挥发油对.OH有明显的清除作用,蜂窝草籽挥发油对实验菌株均有明显的抑制和灭活作用特别是对大肠杆菌ATCC25922株和肠炎沙门菌50040株的抗菌活性表现得更为显著。     

Effects of Water Level on Three Wetlands Soil Seed Banks on the Tibetan Plateau

Background

Although the effect of water level on germination in soil seed banks has been documented in many ecosystems, the mechanism is not fully understood, and to date no empirical studies on this subject exist. Further, no work has been done on the effect of water level on seed banks of drying and saline-alkaline wetlands in alpine areas on the Tibetan Plateau.

Methodology

We examined the effects of water level (0 cm, 5 cm and 10 cm) on seed germination and seedling establishment from soil seed banks at 0–5 cm and 5–10 cm depths in typical, drying, and saline-alkaline wetlands. We also explore the potential role of soil seed bank in restoration of drying and saline-alkaline wetlands.

Principal Findings

Species richness decreased with increase in water level, but there almost no change in seed density. A huge difference exists in species composition of the seed bank among different water levels in all three wetlands, especially between 0 cm and 5 cm and 0 cm and 10 cm. Similarity of species composition between seed bank and plant community was higher in 0 cm water level in drying wetland than in the other two wetlands. The similarity was much higher in 0 cm water level than in 5 cm and 10 cm water levels in all three wetlands. Species composition of the alpine wetland plant community changed significantly after drying and salinization, however, species composition of the seed bank was unchanged regardless of the environment change.

Conclusions/Significance

Water level greatly affects seed bank recruitment and plant community establishment. Further, different water levels in restored habitats are likely to determine its species composition of the plant community. The seed bank is important in restoration of degraded wetlands. Successful restoration of drying and salinization wetlands could depend on the seed bank.     

极度濒危植物-云南蓝果树的种子形态和不同处理条件对种子萌发的影响

观察了云南蓝果树(Nyssa yunnanensis)种子的形态,并初步研究了萌发基质、光照、人工破坏内果皮和pH梯度碱液处理对云南蓝果树种子萌发的影响。结果表明:云南蓝果树种子(带内果皮)平均大小为0.94cm×0.52cm×0.17cm(长×宽×厚),千粒重约234.3g,有萌发瓣;红土/腐殖土/泥炭土(v/v/v,1∶1∶1)为云南蓝果树种子萌发的适宜基质;种子在光、暗条件下都能萌发;人工破坏内果皮能明显地提高种子的萌发率;碱液处理对云南蓝果树种子的萌发有抑制作用,但对中国蓝果树(N.sinensis)种子的萌发有促进作用。本文还对云南蓝果树的致濒原因进行了讨论。     

土壤粒径对极度干旱胁迫下长春花的影响

通过比较草炭土、黄粘土、草炭—黄粘混合基质的粒径组成和土壤样品含水率的变化,分析了黄粘土对长春花土壤保水特性的影响。研究结果表明：极度干旱条件下,随着土壤粘粒比重的增加,长春花叶片的相对含水量、地上地下生物量比值、光合速率、气孔导度、蒸腾速率、水分利用率及可溶性糖的含量都随之增高;完全黄粘土中长春花的水分利用率达到6.975 2 μmol·mmol^-1,为完全草炭土的2倍,可溶性糖中蔗糖的含量也增加到2.614 5 mg·g^-1,海藻糖的含量为0.566 9 mg·g^-1;土壤的保水率也显著增加了30%以上。土壤基质中黄粘土的比例越高,土壤保水性越好,可以为长春花提供更多的有效水。在极度干旱胁迫下,纯黄粘土更适合长春花的生存。     

不同盐处理对盐地碱蓬幼苗肉质化的影响

用不同的钠盐和含Cl-的盐处理盐地碱蓬(Suaeda salsa)幼苗后,测定不同器官的肉质化及相关生理指标,结果表明:NaF处理明显抑制盐地碱蓬幼苗的生长;NaCl处理下生长最好,其中叶片的肉质化程度显著高于对照,正在伸展茎次之,而根则不明显;其次是NaHCO3,肉质化程度也明显高于对照;CaCl2和KCl处理下肉质化程度都与对照相似;MgCl2处理下叶片的肉质化程度明显低于对照.这些结果表明,NaCl处理明显促进盐地碱蓬肉质化是Na 和Cl-两种离子作用的结果,而Na 起主导作用;在这个过程中,HCO3-有一定的作用,Mg2 抑制肉质化.