Effects of harvesting on productivity of bay leaf tree(Cinnamomum tamala Nees & Eberm):Case from Udayapur district of Nepal

Cultivation of bay leaves （Cinnamomum tamalaNees ＆ Eberm） to fulfil household income needs is a long established practice in Udayapur district of Nepal. The practices adopted by farmers for bay leaf harvesting have not, however, been validated by scientific investigation for their sustainability. To investigate the impacts of harvesting on the yield of branch, leaves and biomass of leaves, a two-year research project was conducted in farm fields at Kopche village of Routa VDC in Udayapur district, Nepal. Four different harvesting treatments, the orien-tation and the order of branches were taken as independent variables to test their effects on number of branches, leaves and biomass of leaves. Orientation, harvesting treatments and order of branches had a significant effect on the number of branches, but not on the number of leaves or biomass （fresh and dry weight） of leaves in the year of harvest. Between two consecutive harvests there was no significant difference in the num-ber of branches, leaves or biomass. Lower two-thirds portion of the trees produced the largest number of leaves and branches of the fourth order in both years. Therefore, lower two-thirds portion of the trees were suitable for harvesting. Our findings support farmer experience that no change in productivity of leaves is observed when harvesting each year. For long term sustainability, harvesting should be conducted without debarking of trees or damage to branches. Our findings could be extrapolated to and tested in other areas with different access and user rights where the rota-tion for harvest is fixed or regulated without research evidence.

Resources of Colored-leaf Trees and Their Phenological Ornamental Characteristics in Lhasa City

By using biological five points,expert consultation and fuzzy comprehensive evaluation,the species,phenological ornamental characteristics,and landscape application of colored-leaf trees in Lhasa City were surveyed systematically. The results show that there are 42 species of colored-leaf trees in Lhasa City,belonging to 31 genera and 18 families,of which there are 5,19,and 18 species of spring,autumn,and common colored-leaf trees,accounting for 11.90%,45.24% and 42.86% of total number of the investigated tree species respectively. It is clearly seen that there are too few species of spring colored-leaf trees in the city. There are 19 and 17 species of trees possessing red and yellow leaves,while the leaves of other 6 species of colored-leaf trees are shown in other colors,and the number of their species accounts for 45.24%,40.48% and 14.28% of total number of the investigated tree species respectively. The best ornamental periods of spring,autumn and common colored-leaf trees in Lhasa City average 38.4,41.8 and 251.8 d respectively. Prunus cerasifera Ehrhar f. atropurpurea Rehd.,Ulmus pumila L.,Populus × beijingensis W. Y. Hsu,and Salix alba are applied most frequently in Lhasa City,and their relative frequency is 18.67%,10.29%,9.91% and 8.95% respectively. According to the comprehensive assessment value of their ornamental characteristics,the ornamental characteristics of 15 species of colored-leaf trees in Lhasa City are good or very good,and there is a positive correlation between the comprehensive assessment value and relative frequency. Based on the investigation,the current application situation and problems of colored-leaf trees in Lhasa City were analyzed,and solutions to the problems were proposed.

Effects of Different Water and Fertilizer Combinations on Tree Structure,Leaf Parameters and Photosynthesis of Apple Saplings

[ Objective] This study aimed to investigate the effects of different water and fertilizer combinations on apple saplings. [ Method] ＇ Tianhong 2＇ Fuji /SH40/Malus robusta Rehd. was used as the experimental material to analyze the effects of different irrigation modes and combinations of basal fertilizer and dressing fertilizer on tree structure, leaf parameters and photosynthesis of apple saplings. [ Result] The results showed that different water and fertilizer combinations ex- hibited varying effects on tree structure, leaf parameters and photosynthesis of apple saplings. To be specific, applying 432 000 kg/hm2 basal fertilizer, 480 kg/hm2 urea and 915 kg/hmz organic fertilizer ＋ 0 ＋ 915 kg/hm2 organic fertilizer as dressing fertilizer, and 1% urea as leaf fertilizer was conducive to promoting growth of branches and leaves, increasing leaf thickness, individual leaf area and SPAD, and improving photosynthesis of apple saplings under half root irrigation and whole root irrigation conditions. In addition, the effects were more significant under whole root irrigation conditions. [ Conclusion] Selecting the appropriate water and fertilizer combination is conducive to the growth of apple saplings.

Photoelectric Characterization of Dye Sensitized Solar Cells Using Natural Dye from Pawpaw Leaf and Flame Tree Flower as Sensitizers

Natural dyes from flame tree flower, Pawpaw leaf and their mixtures were used as sensitizers to fabricate dye-sensitized solar cells (DSSC). The photoelectrochemical performance of the Flame tree flower dye extract showed an open-circuit voltage (VOC) of 0.50 V, short-circuit current density (JSC) of 0.668 mA/cm2, a fill factor (FF) of 0.588 and a conversion efficiency of 0.20%. The conversion efficiency of the DSSCs prepared by pawpaw leaf extract was 0.20%, with VOC of 0.50 V;short-circuit current density, JSC of 0.649 mA/cm2 and FF of 0.605. The conversion efficiency for the flame tree flower and pawpaw leaf dye mixture was 0.27%, with VOC of 0.518 V, JSC of 0.744 mA/cm2 and FF of 0.69. Although the conversion efficiencies, Jsc and the Voc of the prepared dye cells were lower than the respective 1.185%, 7.49 mA/cm2 and 0.64V reported for ruthenium, their fill factors (FF) were higher than that of ruthenium (0.497). It was also observed that both the short-circuit current density and the fill factors of the cells were enhanced using mixed dye.

光谱技术在果树叶片营养诊断上的应用研究进展

光谱技术具有分析速度快、操作简单、多元素同时监测、不需要消耗化学药品、自动化程度较高等特点,其可以实现作物单株和大样本的营养诊断和分析。综述了光谱技术在果树叶片大量元素(N、P、K)、中微量元素(Ca、Mg、Fe、Mn、Cu、Zn)营养诊断上的应用研究进展,并讨论了该领域今后进一步的研究方向。

无爪图的支撑k-端点树的存在性

树T中度为1的点称为叶子,叶子数目不超过k的树称为k-端点树.图中存在一个哈密尔顿路,说明图中存在恰好含有两个叶子的支撑树.自然就有了关于哈密尔顿路问题的一个推广:考虑图中至多有k个叶子的支撑树即支撑k-端点树的存在性问题.通过控制集参数,确定了连通无爪图中存在支撑k-端点树条件.

控释尿素与普通尿素配施对橡胶树叶片和胶乳养分及产量的影响

为了明确控释尿素与普通尿素配施在橡胶树上的应用效果,通过2年田间试验,研究了减氮条件下控释尿素与普通尿素不同比例配施对橡胶树产量、叶片和胶乳矿质养分及土壤氮含量的影响,为橡胶树栽培管理中合理施氮提供技术支撑。结果表明:控释尿素与普通尿素配施可提高橡胶树干胶产量和叶片氮含量,与常规施肥相比,橡胶树干胶产量增幅为16.28%~39.13%(2021年)和7.94%~9.69%(2022年),叶片氮含量增幅为10.54%~19.17%(2021年)和10.24%~21.50%(2022年),控释尿素与普通尿素配施处理叶片氮含量均处于正常值以上。控释尿素与普通尿素配施还能够增加胶园肥穴土壤碱解氮含量,较常规施肥增加了11.27%~80.36%。控释尿素与普通尿素配施比例为50∶50时,橡胶树干胶产量(2022年)、叶片氮含量(2021—2022年)和土壤碱解氮含量(2021—2022年)均显著高于常规施肥。综上所述,在本试验条件下,控释尿素与普通尿素配施比例为50∶50能够获得较高的干胶产量,可改善叶片营养状况,维持土壤氮水平,有利于实现橡胶树施肥管理的绿色协同增效。

不同树龄国槐叶片性状特征及其适应策略研究

叶片性状的变异与相关关系能够反映植物的资源利用方式和适应生存策略。为探讨不同树龄国槐叶片性状特征及其变异规律,以聊城市不同树龄国槐叶片为研究对象,通过测定叶面积(leaf area,LA)、叶鲜重(leaf fresh weight,FW)、叶干重(leaf dry weight,DW)、叶长(leaf length,LL)、叶宽(leaf width,LW)、叶柄长(petiole length,PL)、叶厚度(leaf thickness,LT)、叶轴长(rachis length,RL)、叶形指数(leaf shape index,LI)、比叶面积(specific leaf area,SLA)、叶干物质含量(leaf dry matter content,LDMC)、叶组织密度(leaf tissue density,LTD)、比叶重(specific leaf weight,SLW)共13项指标,运用单因素方差分析、变异系数分析探究不同树龄叶片性状特征,经相关性分析、主成分分析探究各树龄国槐叶片的适应规律。结果表明,后备资源的DW、LL、PL极显著高于其他树龄的(P<0.01);国槐13个叶片性状的总体变异系数在8.57%~81.48%,不同树龄叶片性状中后备资源的LTD变异系数最大,为92.86%,2级古树LDMC变异系数最小,仅5.84%;LA、FW、DW、LL和LW呈极显著正相关(P<0.01),SLA与FW、DW、LTD、SLW呈极显著负相关(P<0.01),与LT呈极显著正相关(P<0.01);LDMC与FW、DW、LTD、SLW呈极显著正相关(P<0.01);后备资源叶片性状呈高LDMC、SLW,低SLA的特点,采取的是“快速投资-收益型”策略;2级古树和1级古树呈高SLA,低LDMC、SLW的叶片性状组合,采取的是“缓慢投资-收益型”策略。研究结果为制定不同龄级国槐养护管理策略提供科学依据。

英德野生茶树叶片表型性状的遗传多样性分析

为了解英德野生茶树的叶片表型性状的遗传多样性及进化特点,对英德89份野生茶树资源的表型性状的变异系数、遗传多样性指数、表型分化系数进行分析。结果表明,89份资源的18项叶片性状的变异系数为12.90%~43.11%,平均27.86%;平均遗传多样性指数为1.12,表型分化系数为17.07%~45.51%,平均33.40%。聚类分析结果表明,当欧氏距离为21.5时,所有材料可分为4大类,分类结果与地域分布有一定相关性。巢氏方差分析表明,在不同种群间和种群内,数量性状均有极显著差异。相关性分析表明,叶长与叶宽、叶面积、叶脉对数、叶长宽比、叶形呈极显著相关;叶形与叶长宽比、叶脉对数之间呈极显著相关;叶基与叶宽之间呈极显著相关;叶长宽比与叶尖、着生状态呈极显著负相关。因此,英德野生茶树资源存在丰富的遗传多样性,茶树种质资源类型原始型、进化型以及中间类型并存,但以中间类型和进化型为主。

桃树叶部黑斑病病原菌鉴定及生物药剂田间防效评价

桃树叶部黑斑病是河北省桃树主要的叶部病害之一,致病病原菌种类较多,且与桃穿孔病早期症状相似,容易混淆。因此,明确河北省桃树叶部病害的致病病原菌有利于针对性地防治桃树叶部病害。本研究采集河北省桃树主要种植区典型的桃树病叶,分离纯化获得致病病原菌,利用柯赫氏法则验证病原菌的致病性。根据病原菌形态特征结合rDNA-ITS、EF-1α、Alt-al和RPB2多基因联合序列分析等分子生物学手段鉴定病原菌种类,分离获得39株菌株,明确引起河北省桃树叶部黑斑病的致病病原菌为链格孢菌(Alternaria alternata)。然后采用菌丝生长速率法测定8种杀菌剂对桃树叶部黑斑病致病菌的毒力,发现43%戊唑醇抑制效果最好,EC50值为17.661 mg/L;生物药剂16%多抗霉素、80%乙蒜素,EC50值分别为61.613和87.518 mg/L。基于室内毒力测定结果,对药剂进行了田间防治效果检测,43%戊唑醇对桃黑斑病田间防效为76.86%,生物药剂16%多抗霉素和80%乙蒜素田间防效分别为70.13%和64.93%。本研究筛选出了对防治链格孢菌具有针对性的有效药剂,其中生物药剂具有绿色无污染的特点,指导桃产业生产实践、构建不同商业桃园的绿色防控体系提供了依据。

基于改进版Faster-RCNN的复杂背景下桃树黄叶病识别研究

由于桃树黄叶病(以下简称PTYLD)初期症状不明显,现有的基于深度学习的桃树病害识别技术,存在识别准确率不高、识别品种单一的问题,提出一种基于Faster-RCNN的PTYLD识别模型。为提高模型对PTYLD识别准确率和识别多样性,提出使用RS-Loss函数代替RPN中的交叉熵函数、使用Soft-NMS算法代替原来的NMS算法,来改进Faster-RCNN。通过试验对比初始版和改进版Faster-RCNN对PTYLD的识别效果。试验结果显示,改进后的Faster-RCNN对黄叶病识别的各类别平均准确率mAP达90.56%、召回率达94.16%、准确率达92.53%,能识别常见的五种PTYLD。

Wind induced deformation and vibration of a Platanus acerifolia leaf

Deformation and vibration of twig-connected sin- gle leaf in wind is investigated experimentally. Results show that the Reynolds number based on wind speed and length of leaf blade is a key parameter to the aerodynamic prob- lem. In case the front surface facing the wind and with an in- crease of Reynolds number, the leaf experiences static defor- mation, large amplitude and low frequency sway, reconfigu- ration to delta wing shape, flapping of tips, high frequency vibration of whole leaf blade, recovery of delta wing shape, and twig-leaf coupling vibration. Abrupt changes from one state to another occur at critical Reynolds numbers. In case the back surface facing the wind, the large amplitude and low frequency sway does not occur, the recovered delta wing shape is replaced by a conic shape, and the critical Reynolds numbers of vibrations are higher than the ones correspond- ing to the case with the front surface facing the wind. A pair of ram-horn vortex is observed behind the delta wing shaped leaf. A single vortex is found downstream of the conic shaped leaf. A lift is induced by the vortex, and this lift helps leaf to adjust position and posture, stabilize blade distortion and reduce drag and vibration.

木棉树形结构和叶性状对生境要素的响应研究

植物形态结构是植物本身与外部环境共同作用的结果。为了分析木棉树形结构与叶性状的相关关系,探索地形、土壤和气象要素对木棉生长的影响,以及揭示木棉的生长策略和适应机制,该文以云南省西双版纳国家级自然保护区内230棵木棉为研究对象,测定6个树形结构指标,8个叶性状指标以及所在区域地形、气象、土壤养分等生境要素,使用结构方程模型和变差分解分析各生境要素对木棉树形结构和叶性状的影响和解释度。结果表明:(1)木棉树形结构各观测指标之间、叶性状各观测指标之间存在相关性(P<0.05)。(2)生境要素各观测指标对木棉生长具有较强影响,其中年均降雨量、坡度、平均温度对木棉生长指标的解释率较高,是影响木棉生长的主要生境指标。(3)从标准化路径系数看,3个生境要素对木棉树形结构和叶性状影响具有一致性,均表现为地形要素>气象要素>土壤要素。(4)3个生境要素叠加解释了树形结构和叶性状分别为43.5%和12.3%,表现出树形结构对生境环境的响应大于叶性状对环境响应的特点。研究结果初步探明了木棉不同生长指标对环境要素的适应策略,为木棉在异质生境的培育、繁殖以及木棉人工林高效经营等提供了理论依据和实践参考。

胡杨叶功能性状的协同与权衡及对树龄、土壤因子的响应

【目的】探究不同树龄胡杨叶功能性状的特征及其影响因素,揭示胡杨叶功能性状的种内变异及其适应特性,为胡杨的保护与管理提供理论依据。【方法】以不同树龄的胡杨为研究对象,通过相关性分析和方差分解等方法,研究胡杨叶片形态、光合生理、养分性状的变化特征以及对树龄和土壤因子的响应。【结果】随着树龄的增加,叶干物质含量、叶绿素a含量、叶绿素b含量、叶绿素总量以及叶片碳、氮、磷含量呈增加趋势,而比叶面积、叶厚度呈减小趋势。各叶功能性状之间存在一定的相关性,其中叶绿素a含量、叶绿素b含量、叶绿素总量与叶片碳含量、叶氮含量、叶磷含量、叶干物质含量协同变化,与比叶面积和叶片厚度权衡变化,并且性状间的关系受树龄调控。比叶面积、叶干物质含量、叶绿素a含量、叶绿素b含量、叶碳含量、叶氮含量、叶磷含量主要受土壤pH和树龄的影响,叶片厚度、叶绿素总量主要受土壤氮含量和树龄的影响,表明树龄、土壤pH、土壤全氮含量是胡杨叶功能性状的主要影响因子,并且与土壤因子相比,树龄对叶功能性状变异的解释率更高,可以解释胡杨叶功能性状15.1%~38.1%的变异。【结论】随着树龄的增加,胡杨通过一定的性状变异和性状组合适应环境的变化,各叶功能性状的影响因子不同,其中树龄和土壤因子共同调控叶功能性状的变化,并且树龄在决定胡杨叶功能性状变异方面可能起着更为关键的作用。

东北常见树种叶色季节动态和影响因子研究

【目的】探究东北常见树种叶色季节动态变化及影响因素,以期为揭示植物叶片呈色机理和东北地区园林景观配置提供依据。【方法】本研究选取北美红枫、白桦、紫叶稠李和金叶榆等10种东北常见园林绿化树种为试材,对其色差参数(L*、a*、b*)、色素含量及可溶性糖含量进行测定,并与取样周期内的平均温度进行相关性分析。【结果】不同树种叶片中的色素含量及比例存在显著差异。在整个转色期,叶色季节动态受平均温度和内部各色素含量的综合影响。其中,所有色差参数与叶绿素含量、平均温度呈显著负相关(P<0.05),a*与花色苷含量呈显著正相关(P<0.05)。同时,相关性分析表明,叶片中可溶性糖含量在转色期变化并不显著,与叶色变化无显著相关性。【结论】随平均温度降低,秋色叶黄色树种及红色树种叶片中叶绿素含量逐渐降低。在黄色树种中类胡萝卜素与叶绿素比值升高,而红色树种花色苷与叶绿素比值升高。常色叶树种中紫叶稠李和辽东桤木叶片颜色及色素含量较为稳定,而紫叶李和金叶榆在后期出现复绿现象,分别由于花青素含量降低和叶绿素含量升高导致。

果树凋落叶浸提液对多年生黑麦草和紫花苜蓿的化感效应

【目的】探讨陕北地区红枣、核桃及苹果凋落叶的化感效应,为选择经济林下适生草种提供理论指导。【方法】以室外盆栽牧草多年生黑麦草和紫花苜蓿为材料,设置不同浓度红枣、核桃和苹果凋落叶浸提液(0.1,0.05,0.025,0.0125 g/mL)处理,测定牧草生长和生理指标。【结果】(1)牧草单株干质量在3类凋落叶各浓度浸提液处理下大多比对照显著降低,且红枣浸提液的降幅较小。(2)牧草丙二醛含量在3类浸提液处理下均高于对照,而红枣浸提液的增幅较小,其叶绿素含量、抗坏血酸含量和抗氧化酶活性变化在3类浸提液间存在明显差异,且多年生黑麦草的变幅明显大于紫花苜蓿。(3)3类浸提液对牧草根系性状的影响存在明显差异,均抑制其根长生长,明显抑制多年生黑麦草根尖数,而促进紫花苜蓿根尖数。【结论】3种果树凋落叶浸提液对2种牧草生长多表现出显著抑制作用,并以红枣浸提液的抑制作用最小,且多年生黑麦草生长受抑制程度小于紫花苜蓿。

叶面喷施微生物制剂对苹果树体生长、果实表型性状和叶片营养元素的影响

为了分析叶面喷施微生物制剂对苹果树体生长、苹果果实表型性状和叶片营养元素的影响,设置了3种常用微生物制剂(T_(1):巨大芽孢杆菌菌剂、T_(2):枯草芽孢杆菌剂、T_(3):密旋链霉菌剂),分别按照不同剂量(10、20、30 g/667 m^(2))进行叶面喷施,对比分析了不同微生物制剂在不同施用剂量下对苹果生长、果实及营养指标的影响。结果表明:当T_(1)微生物菌剂的施用剂量为20 g/667 m^(2)时,苹果树冠径、干径、新梢长度、新梢粗度、百叶鲜重、百叶干重等树体的生长情况最佳;当T_(1)微生物制剂的施用剂量为20、30 g/667 m^(2)时,苹果果实单果重、果实横径、果实纵径、果柄粗度等表型性状指标较高,而果柄长度较低;T_(1)、T_(3)微生物制剂的施用剂量为30 g/667 m^(2)时,苹果叶片中的N、P、K含量均较高,且前者的Ca和Mg含量更高;T_(2)微生物制剂在果树树体生长、果实表型性状和叶片营养元素含量方面均低于T_(1)、T_(3)微生物制剂。综上,巨大芽孢杆菌菌剂的施用效果在3种微生物菌剂中最为理想,最佳施用剂量为20 g/667 m^(2)。

香樟树红叶色素的提取及稳定性研究

以香樟树红叶为原料,采用溶剂浸提法提取香樟树红叶色素。以色素特征吸光度为指标,研究红叶色素的提取工艺和稳定性。结果表明:最佳提取工艺为料液比1:40(g/mL)、乙醇体积分数40%、提取温度70℃、提取时间2.5h。稳定性试验得出,在较低温度(20~60℃)、避光条件下,红叶色素的稳定性较好;红叶色素在酸性、中性和弱碱性(pH1~9)条件下稳定,在强碱性(pH10~14)条件下不稳定;红叶色素具有较好的抗氧化性和抗还原性;冰醋酸对红叶色素的稳定性影响不大,而葡萄糖对其有一定影响;金属离子Fe^(2+)、Fe^(3+)、Cu^(2+)Pb^(2+)对红叶色素的稳定性影响明显。通过显色反应得出香樟树红叶色素主要含有二氢黄酮醇类物质。

18种城市园林树种光合耐脱水能力及抗旱性综合评价

随着未来全球气候变化导致的温度上升和蒸气压亏缺增加,筛选耐旱性强的城市园林树种对城市绿化具有十分重要的意义。本研究比较18种城市园林树种的叶光合耐脱水能力(脱水曲线上PSⅡ潜在量子效率开始下降时对应的相对含水量,RWC_(crit))的差异及与叶形态(叶面积、比叶质量、叶干物质含量、叶厚度和叶密度)、解剖结构(气孔密度、气孔长、气孔指数及上表皮、下表皮、栅栏组织、海绵组织、维管束鞘厚度及占横截面面积的比例)的关系和18种园林树种的抗旱能力。结果表明,18种树种的RWC_(crit)在30.2%~58.0%,平均值为44.7%,18种树种的光合耐脱水能力RWC_(crit)与叶面积呈显著正相关,与叶横截面下表皮面积所占比例呈显著负相关,18种园林树种的RWC_(crit)与其综合抗旱能力变化趋势一致。研究结果表明,RWC_(crit)可以作为耐旱性指标预测园林树种的耐旱性,对未来城市耐旱树种筛选和合理经营有一定价值。

大花紫薇幼苗对水分胁迫及解除的生长响应

[目的]分析不同水分处理对抗性树种大花紫薇Lagerstroemia speciosa生长的影响,探究大花紫薇形态性状的响应机制,为抗性园林树种的选择及水分管理提供理论依据。[方法]以大花紫薇的1年生幼苗为材料,设置干旱(DR)、水淹(WL)、水淹-干旱交叉(WD)和对照(正常浇水,CK) 4种水分处理,开展30 d水分胁迫试验,随后解除水分胁迫,并维持DR、WL、WD处理组植株的土壤水分在CK水平,进行为期30 d的恢复生长,测定水分胁迫及解除后植株的叶性状、根系性状和生物量指标。[结果]DR、WD胁迫终期和WL恢复终期的总叶面积相较CK显著下降;3种水分胁迫处理的叶组织密度在胁迫终期相较CK显著上升,比叶面积在恢复终期显著下降。胁迫终期时,WL和WD处理提升了细根根长占比和细根表面积占比;恢复终期时,DR、WL、WD处理的细根表面积占比分别比CK升高了9.59%、12.42%、13.57%;胁迫终期和恢复终期时,WL处理的比根长和比根面积显著高于CK。胁迫终期时,3种水分胁迫下的植株增加了对茎的生物量分配,且WL处理植株生长的不定根占总根系生物量的26.95%;DR胁迫终期和恢复终期的根系生物量分配显著升高,根冠比分别相比各自CK提升了40.93%和70.06%。相关性分析表明,叶性状间、根系性状间分别存在权衡关系;根长、根表面积与叶组织密度呈显著正相关。[结论]大花紫薇叶-根系性状间存在一定的相关性;短期的水分胁迫对大花紫薇幼苗根系生长具促进作用,使其更好地适应城市园林绿地复杂多变的水环境。