Antioxidant Activity and Phytochemical Screening in Acacia rigidula Benth. Leaves

This study aimed to compare the total phenolic content (TPC) and antioxidant activities of A. rigidula extracts. It also aimed to identify phenolic acids present in the extracts. The 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and ferric thiocyanate lipid peroxidation antioxidant assays were performed. High performance liquid chromatography was used to identify phenolic acids. There was no solvent effect on TPC nor on scavenging activities, and inhibition of lipid peroxidation (p > 0.05) among solvent extracts. On the other hand, 1:1:3 water: acetone: methanol extract (10.22 mg GAE/g sample) had significantly higher reducing potential than 50% ethanol extract (EE) (9.259 mg GAE/g sample) (p < 0.05);but EE was not significantly different from 80% methanol extract (9.781 mg GAE/g sample) (p > 0.05). Phenolic fraction designated as fraction 4 had the highest antioxidant activity (p < 0.05) with 69.49% ABTS scavenging activity and FRAP reducing potential, 22.26 mg of GAE/g sample. DPPH scavenging activities of fractions 4 (55.59%) and 5 (55.64%) were significantly higher than the other fractions (p A. rigidula extracts contain gallic, caffeic, vanillic, p-coumaric, salicylic acids and vanillin.

Tannins from Acacia mangium Bark as Natural Dyes for Textiles:Characteristics and Applications

Tannins are capable of producing natural dyes with antioxidant and antibacterial propertis,while synthetic dyes are commonly used in the textile industry,causing environmental issues like water pollution.This research aims to utilize waste tannins as natural dyes as an alternative to synthetic dyes.This study examined the effect of the extraction method on tannin properties such as phenolic content,antioxidants,and antibacterial activity.In addition,Pyrolysis Gas Chromatography‒Mass Spectrometry(Py-GCMS)analysis was used to identify the effect of extraction temperature on the chemical elucidation of tannin.The effect of tannin concentration was evaluated against four bacteria that are usually found on human skin:Staphylococcus epidermidis,Bacillus subtilis,Propionibacterium acnes,and Staphylococcus aureus.Extraction temperature significantly influences the chemical composition of tannin,which leads to different antioxidant properties.The maximum antibacterial properties of tannin were obtained at 90℃with the inhibition zone in the range of 0.9–1.0 mm against four bacteria,tannin yield of 26.59%,Gallic Acid Equivalents or total phenolic content(GAE)of 40.30 mg/g,and Radical Scavenging Activity or antioxidant activity(RSA)of 89.88%.Moreover,the concentration of tannin was significantly linear with its antibacterial properties.Tannin was successfully applied to the textile by using alum as a mordanting agent to create an antibacterial textile.The textile’s bacterial structure damage was analyzed under Field Emission Scanning Electron Microscopy(FESEM).After 50 washings,tannin-textiles with alum-modified properties remained stable compared to those without alum,with S.aureus and S.epidermidis being the most vulnerable bacteria,as confirmed by FESEM images.Hence,tannin is a feasible alternative to harmful and nondegradable synthetic dyes and antibacterial agents.

Structural Elucidation of the Polymeric Condensed Tannins of Acacia nilotica Subspecies by ^(13)C NMR, MALDI-TOF and TMA as Sources of Bioadhesives

Tannin was extracted from different subspecies of Acacia nilotica,Acacia nilotica nilotica(Ann),Acacia nilotica tomentosa(Ant)and Acacia nilotica adansonii(Ana).The aim was to elucidate their structure and evaluate their reactivity as bioadhesives in the wood industry.The extracts were prepared by hot water extraction(90°C tem-perature).Their gel time with paraformaldehyde was used atfirst to compare their reactivity.The tannin contents and the percentage of total polyphenolic materials in different solutions of the extracts spray dried powder were determined by the hide powder method.Concentrated solutions(47%)were tested by both MALDI ToF,13CNMR.The thermomechanical analysis(TMA)was performed to evaluate their modulus of elasticity(MOE)at different pHs.The gel times of all the three tannin extracts showed that their reactivity and it was com-parable to other known procyanidin/prodelphinidin tannin extract types.Ana,Ann and Ant showed highest per-cent of total polyphenolic materials at 70%,64%,and 57%,respectively.The 13CNMR spectra showed that the three subspecies of condensed tannins were mainly constituted of procyanidins(PC)and prodelphinidins(PD)in slightly different ratios.Ann(56.5%PC and 43.4%PD),Ant(57%PC and 43%PD)and Ana(58%PC and 42%PD).MALDI–TOF spectra showed the presence offlavonoid monomers,and oligomers some of which linked to short carbohydrates monomers or dimers.TMA revealed that the three types of tannins had high MOE at their initial pH(5).

Phylotranscriptomic discordance is best explained by incomplete lineage sorting within Allium subgenus Cyathophora and thus hemiplasy accounts for interspecific trait transition

The transition of traits between genetically related lineages is a fascinating topic that provides clues to understanding the drivers of speciation and diversification.Much can be learned about this process from phylogeny-based trait evolution.However,such inference is often plagued by genome-wide gene-tree discordance(GTD),mostly due to incomplete lineage sorting(ILS)and/or introgressive hybridization,especially when the genes underlying the traits appear discordant.Here,by collecting transcriptomes,whole chloroplast genomes(cpDNA),and population genetic datasets,we used the coalescent model to turn GTD into a source of information for ILS and employed hemiplasy to explain specific cases of apparent“phylogenetic discordance”between different morphological traits and probable species phylogeny in the Allium subg.Cyathophora.Both concatenation and coalescence methods consistently showed the same phylogenetic topology for species tree inference based on single-copy genes(SCGs),as supported by the KS distribution.However,GTD was high across the genomes of subg.Cyathophora:~27%e38.9%of the SCG trees were in conflict with the species tree.Plasmid and nuclear incongruence was also present.Our coalescent simulations indicated that such GTD was mainly a product of ILS.Our hemiplasy risk factor calculations supported that random fixation of ancient polymorphisms in different populations during successive speciation events along the subg.Cyathophora phylogeny may have caused the character transition,as well as the anomalous cpDNA tree.Our study exemplifies how phylogenetic noise can be transformed into evolutionary information for understanding character state transitions along species phylogenies.

Effect of Acacia albida Leaf Supplementation on Reproductive Parameters and Pre-Weaning Growth of Arabian Lambs

A trial on Acacia albida leaf supplementation on reproductive parameters and pre-weaning growth of Arabian lambs was conducted from September 2020 to May 2021 at the small ruminant station of the Livestock Research Institute for Development (IRED) in N’Djamena, Chad. Forty-eight (48) Arabian sheep (45 non-pregnant females and 3 males for a sex ratio of 1 ram to 15 ewes) with an average weight of 20.3 ± 1.2 kg and aged approximately 2 years were divided into 3 groups of 15 ewes each. The supplemented group received in addition to the dominant forage of the pasture (300 g of Dactyloctenium aegyptium + 300 g of Cenchrus ciliaris + 600 g of Panicum maximum), 400 g and 600 g of Acacia albida leaves/animal/day while the control group received only 300 g of Dactyloctenium aegyptium + 300 g of Cenchrus ciliaris + 600 g of Panicum maximum. From the results of this study, it appears that the ewes that received 400 g of Acacia albida leaves had a significantly higher fertility rate and birth mortality rate (93.03% and 6.25% respectively). Animals in the control group had a significantly higher pre-weaning mortality rate than those receiving Acacia albida leaves as a supplement (16.66% versus 6.66% and 14.28% respectively). The highest weight of the lambs was observed in the ration supplemented with 600 g of Acacia albida leaves (12209.66 g). The total weight gain, as well as the average daily weight gain of the lambs receiving the 600 g Acacia albida leaf ration was significantly higher than those of the other rations. Supplementation with 400 g and 600 g of Acacia albida leaves can be recommended as a protein supplement for breeding ewes and pre-weaned lambs.

Antimicrobial activities of Acacia genus:A review

More than 1 300 species of the vast genus Acacia are found in tropical habitats. They are crucial economic plants since they produce traditional medicines, timber, and gum. The pharmacological uses of the Acacia genus include anti-diarrheal, anti-malarial, chronic pain relief, wound healing, anti-cancer, anti-rheumatism, and antidiabetes activities. It is also used for treating various illnesses such as gastroenteritis, allergies, Alzheimer’s disease, cough, and cardiovascular disease. The present review aims to summarize the antimicrobial activities including the antibacterial and antifungal activity of the Acacia genus. The literature was searched in books and online databases including SciFinder, Google Scholar, Scopus, Pub Med, and scientific journals using the most relevant keywords: Acacia+antimicrobial, Acacia+antibacterial, and Acacia+antifungal.

Determinants of Smallholder Farmers Adoption of Acacia decurrens in Northwest Ethiopia

Planting a fast-growing multipurpose Acacia decurrens (AD) tree is one of the climate-smart agricultural practices that have been promoted in Ethiopia, which is widely practiced and an important livelihood strategy in Awi zone. However, the extent of its adoption varies considerably among households in the study area. This study investigated the determinants of intensity of adoption of AD among 385 randomly selected rural households in Awi Zone. Data were gathered using a cross-sectional household survey. Descriptive statistics and Two-limit Tobit model were employed for data analysis. The result of the study shows that on average the intensity of adoption of AD was 0.43 (43% of the total cropland area), though majority of the farmers (48.8%) belong to low level of adoption. The result of the analysis shows that being male, educational level, access to seedling, experience in growing the tree, extension contact has positive and significant relationship with the intensity of adoption. Age of head of household, land holding size, livestock holding size, soil fertility status, disease emergence and road distance have negative and significant influence on intensity of adoption. These suggest that expanding road infrastructure, education, access to seedling, secure land property right, disease management, and provision of extension services related to the AD can also improve smallholder farmers’ intensity of AD adoption. The generated information provides a picture of the study area’s situation to the attention of policy makers, development practitioners and institutional service providers to formulate a better policy intervention to sustain smallholder farmers’ AD plantation.

Survival of Seedlings of Native Woody Species in the Rehabilitation of Gold Mined-Site within a Three Years Old Acacia mangium Willd Plantation of St. Elizabeth-Mahdia, Guyana

Active restoration is a critical component of biodiversity conservation for degraded tropical forest ecosystems caused by artisanal gold mining, and the success of restoration is dependent on native species selection. However, significant knowledge gaps exist regarding when and where to plant trees. This article reports on a revegetation trial undertaken in St Elizabeth, Mahdia, Guyana, to assess the survival and RGR (Relative Growth Rate) of three native woody trees and shrubs planted within three years old Acacia mangium Willd trees pruned and unpruned blocks. ANOVA (Analysis of Variance) for a completely randomized block design with four blocks, two pruned and two unpruned, within A. mangium plots. Biochar treatment was added to the plants during transplanting. Thirty-six (36) wildlings of Humiria balsamifera (Aublet.) (Tauroniro), Goupia glabra Aublet (Kabukalli), and Vismia guianensis (Aublet.) Choisy (Bloodwood) were collected and raised in a tree nursery for two weeks. The native plants were transplanted 3 m apart, survival observations and each seedling’s initial height and diameter were measured and recorded. After the experiment, 13% of seedlings from a population of 720 had died, with the highest mortality being experienced at the 92 days of the experiment (t ≤ 122 days). While the overall survival rates were high, emphasizing the importance of field trials on native and exotic species in different environments is essential to fill the knowledge gaps on suitable species for restoration in degraded areas with other land use histories.

科研反哺教学创新型综合实验——银叶金合欢叶总黄酮提取工艺及抗氧化性研究

将最新科研成果转化为教学内容,激发学生学习兴趣。将银叶金合欢叶总黄酮的提取工艺及抗氧化性研究的科研内容转化成适用于化学、化工、制药专业开设的创新型综合实验。以广西崇左市银叶金合欢叶为原料,经超声波辅助法提取总黄酮,通过单因素试验考察提取工艺条件,并进一步研究银叶金合欢叶总黄酮的抗氧化活性。本实验涉及多学科内容的交叉和融合以及应用,不仅能够培养大学生运用所学理论知识和实验技术解决实际问题的能力,还能激发大学生的科研热情,提升学生的综合实践能力和创新思维能力。

盐胁迫对台湾相思幼苗形态及相关生理指标的影响

为探寻台湾相思种子的耐盐情况,在其种子萌发期和幼苗期分别进行不同浓度盐胁迫试验。结果表明:低浓度NaCl胁迫可提高种子发芽率,随着NaCl浓度的增高,种子发芽势、发芽率、活力指数以及发芽指数均不同程度降低,且和对照有显著差异。通过拟合台湾相思发芽率和NaCl胁迫浓度回归曲线,发现种子萌发期台湾相思适宜的最大NaCl胁迫浓度为203.87 mmol∕L,NaCl致死浓度为383.16 mmol∕L;幼苗期台湾相思叶鲜重、茎鲜重、根鲜重、主根长、株高、地径以及叶片数等指标在NaCl胁迫下呈下降趋势,根冠比先上升后下降,植物的总根长、总根表面积、总根投影面积、总根体积、根平均直径、总根尖数、分枝数、交叉数均和NaCl浓度呈负相关,NaCl胁迫适宜的最大浓度为49.28 mmol∕L,台湾相思幼苗SOD、POD活力及MDA、PRO含量随着NaCl胁迫浓度的增加呈现先增高后降低的趋势。

黑木相思家系适地适树品种综合评价

[目的]为选出适宜南方山地的黑木相思家系,揭示黑木相思长势土壤养分的空间分异规律与地形变化的关系。[方法]本文以杉木采伐迹地上营造的15年生7个黑木相思家系(M1~M7)为研究对象,采用经典统计学、描述性统计、地统计学方法和GIS技术,研究了7个黑木相思家系分别在不同坡位的土壤理化性质的变化规律和土壤养分的空间分布,并通过因子分析法和模糊评价法对7个黑木相思家系进行综合评价选优。[结果]7个黑木相思家系的理化性质在不同坡位的含量大多表现为下坡位>中坡位>上坡位,下坡位显著高于其他坡位;家系间土壤结构和养分含量均表现出M7、M6和M5较好;研究区各养分含量总体呈块状或条带状分布,呈现从东北和西北方向往南方向递增的趋势。[结论]综合评价值在上下坡位黑木相思家系M7值最高,其生长对土壤理化性质的改良效果最佳,在中坡位黑木相思家系M6最佳。研究结果对南方山地适地适品种和可持续发展研究具有参考价值,可用于黑木相思人工林经营管理实践中。

不同模式桉树混交林的生长效应分析

为探索伴生树种早期对桉树生长的影响,以桉树×红椎、桉树×火力楠、桉树×火力楠×黑木相思、桉树×黑木相思4种混交林为研究对象,对其林木生长量及桉树在不同混交模式中的生长效应进行分析。结果表明:4种混交模式下混交树种早期生长量均优于其纯林生长量。桉树×火力楠对桉树树高促进作用最大,增量为4.94±1.57 m;桉树×火力楠×黑木相思对桉树胸径和材积促进作用最大,增量分别为2.47±0.70 cm和0.8695±0.7066 m^(3)•hm^(−2)。总体以桉树×火力楠×黑木相思混交模式最优。

马占相思 (Acacia mangium)与湿地松 (Pinus elliotii)人工林枯落物层的水文生态功能

分析了马占相思与湿地松人工林枯落物的蓄积量、年凋落量及凋落动态、枯落物层对大气降水的截留、以及枯落物抑制土壤水分蒸发和阻滞径流的效应。结果表明 :1 1 5龄的马占相思林枯落物蓄积量 32 .3t/hm2 ,年凋落量 1 1 .1 4 t/hm2 ,最大持水率 2 53.7% ,最大持水量 2 8.2 6t/hm2 ;1 5龄的湿地松林枯落物蓄积量 1 8.7t/hm2 ,年凋落量 7.30 t/hm2 ,最大持水率 2 1 6.7% ,最大持水量 1 5.82 hm2 ;2 2种林分对大气降水的截留率分别为 1 5.9%和 1 1 .7% ,截留率随 1次降水降水量 ( >1 0 mm)的增加而减少 ;3 2～ 4 cm枯落物覆盖下不同含水量的土壤水分蒸发比无覆盖的土壤减少 1 8.2 %～ 78.3% ,枯落物层减少土壤水分蒸发的效应随枯落物层厚度和土壤含水量的增大而增加 ;4 2种枯落物对径流流出时间的阻滞效应随径流深 ( <3mm)和坡度的增加而减小 ,随枯落物层厚度的增加呈直线增加。通过与部分其它森林类型枯落物层水文生态功能比较 。

不同年龄阶段马占相思(Acacia mangium)人工林营养元素的生物循环

对马占相思人工林6种营养元素(N、P、K、Ca、Mg、S)的含量、积累、分布和生物循环特点以及随林分年龄的变化趋势进行了研究。结果表明:(1)林木不同组分营养元素含量的大小次序为树叶>干皮>活枝>枯枝或树根>干材;各组分和凋落物中营养元素含量以N最高,其次是Ca或K,然后是S和Mg,P最低;林地土壤中,以K的含量最高,其次是Ca、Mg、N和P,S最低;随林龄的增加,0～40cm土壤N、P和S含量呈增加趋势;(2)4年、7年生和11年生林分营养元素总积累量分别为1022.08、1997.08和2633.45kg.hm-2,其中乔木层营养元素贮存量依次占73.64%、82.39%和83.65%,林下植被层依次占13.74%、8.74%和6.20%,地表现存凋落物层依次占12.62%、8.87%和10.16%;乔木层以N积累量最大,占总贮存量的53.90%～60.07%,P最小,仅占0.90%～1.23%;(3)马占相思林中不同组分营养元素积累量的分配随林龄的增长发生变化,由4年生以树叶和树枝占主导,逐渐转移到7年生和11年生以干材和树皮为主导;(4)林分营养元素年积累量依次为7年生(235.06kg.hm-.2a-1)>11年生(200.26kg.hm-.2a-1)>4年生(188.16kg.hm-.2a-1);林木各组分营养元素年积累量总的变化趋势为:树干>树叶>树枝>根系>树皮,同一组分各营养元素年积累量与各组分营养元素积累量变化顺序一致,即为N>Ca>K>S>M>P;(5)林分营养元素年吸收量分别为382.35、432.04kg.hm-.2a-1和403.15kg.hm-2.a-1,年归还量分别为194.19、196.98kg.hm-.2a-1和202.89kg.hm-.2a-1,营养元素的循环系数分别为0.51、0.46和0.50,利用系数为0.51、0.26和0.18,周转期为3.88、8.35和10.86。可见,马占相思人工林早期营养元素利用率低,归还速率较快,林分生长到近熟期(11a)时营养元素的周转期较长,但其归还速率仍然较快,有利于林地地力的恢复、维持和提高。

马占相思(Acacia mangium)树干液流密度和整树蒸腾的个体差异

利用Granier热消散探针观测了华南丘陵地区马占相思人工林（18a树龄）的树干液流（Sap Flow）。日变化的观测结果显示，不同大小胸径的14株样树液流密度（山）个体间的差别较大（CV：36．42％-80．80％），日间最大液流密度从最高的80．05（gH2Om^-2s^-1）到最低的11．25（gH2Om^-2s^-1），差异显著。液流密度的个体差异与树形的大小并不显著相关（P〉0．24），即液流密度的大小不是与树木形态相关联的固有特征。然而，树木胸径的大小却是影响液流随时间变化的重要因子。树形较大的树木日总液流量（E1，kgH2Otree^-1d^-1）较高，但中等大小的树木却具有较高的单位基面积日液流量（E2，kgH2Odm^-2d^-1），发现，单位基面积的日流量最大值并不出现在胸径最大的树木，而出现在胸径稍小的树木，意味着后者对自身结构的水分利用效率较高。由液流密度计算的整树蒸腾，个体间差异也比较大（3．35—72．42kgH2Otree^-1d^-1），且与胸径以幂函数的形式呈现正相关（P〈0．001）。尽管整树蒸腾在个体之间的差别较大，但随时间的变化规律却是一致的，整树蒸腾的变化格型基本上受环境因子的控制。以液流反映马占相思的蒸腾与冠层的实际蒸腾存在明显的时滞，14株样树的液流变化比光合有效辐射滞后40,in至110,in，相关分析显示，时滞的长短与树木的胸径、高度、边材面积和冠幅均不呈现明显的相关性（P〉0.36）。

基于树干液流测定值的马占相思(Acacia mangium)冠层气孔导度计算及数值模拟

为深入揭示华南地区马占相思冠层气孔导度对环境因子的响应规律,在2005年7月至11月,利用Granier热消散式探针法对马占相思(Acacia mangium)的树干液流(sapflow)进行了连续测定,计算出整树的蒸腾,并由Penman-Monteith方程得出马占相思的冠层气孔导度值。通过分析,发现:马占相思冠层气孔导度是控制马占相思树整树蒸腾的主要因素;冠层气孔导度随着水汽压亏缺增加呈负指数函数下降的趋势。使用包括了太阳总辐射、水汽压亏缺和气温的Jarvis模型可以较好地模拟马占相思冠层气孔导度对环境因子的响应特征;模拟结果表明:环境变量对模型精确度的影响程度依次为:水汽压亏缺>太阳总辐射>气温。

厚荚相思(Acacia crassicarpa)腋芽组培快繁技术体系研究

以16年生厚荚相思优树新生带腋芽茎段为外植体进行组织培养和快繁体系建立的研究,结果表明:含腋芽茎段经75%酒精和0.1%升汞分别处理30S和12min后,接入MS+蔗糖2%上进行初代培养,存活率为67.33%,芽诱导率为80.56%;低浓度的活性炭可有效缓解组培苗玻璃化现象,最佳增殖培养基为改良MS+6-BA0.5 mg·L-1+NAA 0.25 mg·L-1+Ac 0.1 g·L-1+蔗糖3%,35 d增殖倍数可达3.72;最佳生根培养基为改良MS+IBA 0.5 mg·L-1+蔗糖2%,生根率为98.83%;将生根苗移栽至以黄心土为基质的营养杯中,存活率为90.00%。

电场处理对卷荚相思种子萌发特性的影响

【目的】分析不同电场、时间及两者交互处理对卷荚相思种子萌发特性的影响,为卷荚相思种子萌发及可持续经营提供理论参考。【方法】以卷荚相思种子为研究对象,采用室内模拟试验,以不同电场强度和处理时间为控制因素,电压强度为0.0、0.2、0.4、0.6、0.8、1.0 kV·cm^(-1),时间处理为0、15、30、45、60 min,研究不同电场强度和时间交互处理对其种子萌发特性的影响。【结果】随着电场强度增强,处理时间的延长,卷荚相思种子的发芽率、发芽势和发芽指数均呈现不同程度的变化趋势。其中,在处理时间15、30、60 min下发芽率随着电场强度的增强呈现先降后升再降的趋势,但在处理时间45 min下发芽率随着电场强度的增强呈现先升后降的趋势;而发芽势和发芽指数均在电场强度0.6~0.8 kV·cm^(-1)和处理时间45 min下处于最优状态,且与CK相比具有显著差异(P<0.05)。经过多元非线性回归分析得出,不同电场强度与时间交互处理下的最优回归方程为:Y=7.73+135.23X_(1)+1.24X_(2)-86.16X_(1)^(2)-0.00911X_(2)^(2)-0.75X_(1)X_(2)(R^(2)=0.81,P<0.05)。聚类分析结果电场和时间交互环境处理对发芽指数有非常显著的影响。【结论】电场和时间两者交互处理对卷荚相思种子萌发特性具有一定的影响,发芽率在0.6 kV·cm^(-1)处理45 min最高,说明适宜电场强度和处理时间可以提高卷荚相思种子发芽率。

不同径级马占相思(Acacia mangium)整树蒸腾的湿、干季变化

利用Granier树干液流测定系统对广东鹤山丘陵地马占相思（Acacia mangium）林进行长期监测,并同步监测环境因子（空气温度、相对湿度、光合有效辐射、土壤体积含水量）,选择胸径具有代表性的样树,结合马占相思的形态学参数,计算马占相思的整树蒸腾。通过对光合有效辐射（PAR）分级,建立不同辐射强度等级的湿季（土壤水分θ≥33%）整树蒸腾与水汽压亏缺（VPD）的相关方程,以干季（θ≤24%）的VPD代入对应PAR等级的湿季的拟合方程,求出干季的潜在蒸腾,以潜在蒸腾和干季实际蒸腾之差分析不同径级整树蒸腾在不同季节的实际变化。在所有的PAR分级内,干季整树蒸腾显著低于湿季,仅占湿季蒸腾的10%-20%,就蒸腾减少的绝对量而言,优势木〉中间木〉劣势木。土壤水分下降缩小了不同径级树木之间液流密度的差异,土壤水分亏缺限制了树木的蒸腾,对马占相思的生长造成一定程度的水分胁迫。

模拟氮沉降对木荷和卷荚相思种子萌发的影响

【目的】研究氮沉降对2种林木种子萌发的影响,为南方森林的经营管理提供参考。【方法】以木荷和卷荚相思种子为试验材料,采用室内试验,选择2,6和12 g/L硝态氮(KNO 3)、铵态氮((NH_(4))_(2)SO_(4))、混合氮(NH 4NO 3)进行氮沉降模拟试验,以蒸馏水为对照(CK),测定各处理木荷和卷荚相思种子的发芽率、相对发芽率、发芽指数、活力指数和发芽抑制率,在此基础上采用主成分分析综合评价不同处理对种子萌发的影响。【结果】随着KNO 3、(NH_(4))_(2)SO_(4)、NH 4NO 3质量浓度的升高,木荷和卷荚相思种子的发芽率、相对发芽率、发芽指数和活力指数均呈下降趋势,而发芽抑制率逐渐提高。由上述5种发芽指标可知,同一氮源下,其不同质量浓度对木荷和卷荚相思种子萌发的促进作用均表现为2 g/L>6 g/L>12 g/L;同一质量浓度下,3种氮源中以(NH_(4))_(2)SO_(4)对木荷和卷荚相思种子萌发的促进作用最佳。主成分分析结果显示,木荷和卷荚相思均以主成分1能够反映原始变量80%以上的信息,因此选择主成分1对不同处理进行综合排名,结果在木荷和卷荚相思种子各处理中综合排名第1的均为2 g/L(NH_(4))_(2)SO_(4)处理。【结论】当质量浓度为2~12 g/L时,3种氮源对木荷和卷荚相思种子萌发的影响有差异,但最适宜的处理均为2 g/L(NH_(4))_(2)SO_(4)。