不同种源白刺幼苗生理生长对水分梯度的响应差异

在乌兰布和沙漠东北部地区,依据多年平均月降水量,对5个种源的白刺幼苗进行极度干旱、干旱、轻度干旱和正常降雨水平4种不同的水分梯度处理,开展水分梯度试验.通过测定不同水分梯度、不同种源的光合生理指标表明:水分梯度显著影响白刺幼苗的净光合速率、蒸腾速率、气孔限制值、气孔导度、光合水分利用效率、表观光能利用效率、表观CO2利用效率等生理生态特征,并影响植株的苗高和最大新枝长等生长量指标;不同种源之间的净光合速率、水分利用效率、表观光能利用效率、表观CO2利用效率存在显著差异,且在苗高和最大新枝长之间也存在显著差异,但不同种源、不同水分梯度对幼苗的地径均无显著影响.相比于临河、乌拉特后旗种源,磴口、阿拉善盟和民勤种源的蒸腾速率和资源利用效率在不同水分处理之间表现出显著差异,且3个种源的各个资源利用效率都较大.白刺幼苗在光合活动中的气体交换及资源利用效率的生理反应和外在的生长量表型指标的差异,反映了各白刺种源对不同水分环境表现出的响应差异.     

印楝不同种源对温度变化的光合生理生态响应

利用Li-6400P便携式光合作用测定仪在大气CO2浓度370±10 μmol·mol-1、空气相对湿度65%±5%及一定光合有效辐射(PAR)条件下,研究了印楝4个种源的净光合速率(Pn)、气孔导度(gi)、蒸腾速率(E)、光呼吸(Pr)和暗呼吸(Rd)等生理生态指标对温度变化的响应,结果表明:印楝不同种源光合生理生态指标对温度的变化极为敏感,印楝种源间Pn对温度的响应曲线呈抛物线型,在不同的生长季各种源的Pn最适温度不同,生长初期为2829 ℃,盛期为32 ℃左右,生长末期为30 ℃,同等条件下,同一种源的Pn值生长盛期＞初期、末期,不同种源的Pn值Kalyani(KA)种源>New Delhi(CK)种源>Jodhpur(MA)>Kulapachta(KU)种源;印楝不同种源的gi和E随温度变化在生长初期和末期呈抛物线型,而盛期则呈直线型,同等条件下,种源间的gi和E的大小排序略有差异,总体上为KA＞CK＞MA＞KU;印楝种源间Pr和Rd随着温度升高都呈指数增长态势,同温条件下,暗呼吸值大于光呼吸,二者在不同生长季节的排序为生长初期＞盛期＞末期,而在同一生长期内,种源间Pr和Rd大小排序为KA＞CK＞MA＞KU.     

光照对沙棘幼苗生长、生物量分配及光合特性的影响

为探索沙棘幼苗对光照强度的适应性,通过设置100%光照强度、60%光照强度、20%光照强度3个光照梯度,分析沙棘幼苗的生长、光合特性及生物量分配特征对不同光环境的响应。结果表明:光照显著促进沙棘幼苗的生长,苗高、基径、冠幅、叶长、叶宽、叶面积、净光合速率等指标均在100%光照强度下最大,而且均随光照强度的减弱而减小;沙棘幼苗的根、茎、叶和单株生物量均在100%光照强度下最大;根冠比、叶生物量比、茎生物量比及根生物量比在3种光环境下无显著差异;沙棘幼苗通过改变光合特性和生物量积累来适应光环境的变化,其中光照强度的降低限制了生物量的积累,但并未显著改变生物量在地上和地下部分的分配比例,在3种光环境下生物量分配比例并无显著的改变;幼苗的比叶面积随着光照强度减弱而增大,在20%光照强度下达到最大值。     

氮沉降模拟对不同种源木荷幼苗叶片生理及光合特性的影响

以浙北、闽北和赣南3个木荷代表性种源为试验材料,比较不同氮沉降水平下,木荷幼苗叶片的光合-光响应曲线、氮和磷含量、光合色素含量及可溶性蛋白含量之间的差异.结果表明:(1)中、低氮沉降水平促进了木荷幼苗叶片的光合能力,降低了呼吸消耗,叶片氮含量及叶绿素含量增高,叶片磷含量及可溶性蛋白含量降低,光合同化物易于积累;而高氮沉降水平时对光合能力的促进作用减小甚至产生危害.(2)木荷不同种源间叶片利用光能的程度差异较大,浙江杭州种源净光合速率较高,利用弱光的能力强,易发生光抑制现象,光合同化物不易积累;福建建瓯种源利用强光能力强,暗呼吸速率较低,同化物最容易积累;江西信丰种源光合能力和暗呼吸速率介于浙江杭州和福建建瓯种源之间.(3)低氮沉降水平对北部浙江杭州种源促进性强,叶片叶绿素和可溶性蛋白含量增加,光合能力增强,同时暗呼吸速率降低;中氮沉降水平对福建建瓯种源生产力促进最大,而叶绿素及可溶性蛋白含量在此水平下却较低;低氮沉降水平显著促进了南部江西信丰种源的净光合速率及利用弱光能力,呼吸消耗却并未显著增长,叶片可溶性蛋白增多.因此,在森林土壤磷含量较低的环境下,木荷育种不仅要考虑不同种源间的生长差异,同时也要充分考虑氮沉降的影响,才能达到最佳效果.     

不同营养条件对黎蒴栲苗木形态指标的影响

采用均匀设计对黎蒴栲实生幼苗进行不同梯度的N、P、K配比施肥试验,探讨不同营养条件对黎蒴栲幼苗苗高、地径、冠幅的影响。结果表明：1）不同营养条件对黎蒴栲幼苗的形态指标有很明显的影响。T5（N：0.075 0 g/株、P2O5：0.350 0 g/株）施肥处理的苗高、地径、冠幅较大,其次为T4（N：0.112 5 g/株、K2O：0.050 0 g/株）、T3（P2O5：0.175 0 g/株、K2O：0.100 0 g/株）施肥处理,T1（N：0.150 0 g/株、P2O5：0.262 5 g/株、K2O：0.150 0 g/株）、T2（N：0.037 5 g/株、P2O5：0.087 5 g/株、K2O：0.200 0 g/株）施肥处理和对照则较差。2）N、P、K对黎蒴栲幼苗生长的影响效应各不相同。氮肥可促进黎蒴栲幼苗的生长,但过多的钾肥则不利于黎蒴栲幼苗的生长。     

3个与杉木混植木荷种源幼苗对光照响应的差异

目的]探寻不同木荷种源混交林生产力差异的光合机制。[方法]以福建建瓯、江西信丰和浙江龙泉3个木荷代表性种源1年生和2年生幼苗为试验材料,在与杉木混植条件下,设置100%(L0)、50%(L1)和25%(L2)3种光照的光环境,研究3个木荷种源幼苗的生长性状、光合生理及叶绿素荧光特性等对不同光照响应的差异。[结果]1年生和2年生木荷幼苗的苗高、地径和干质量均表现出显著的种源差异,福建建瓯种源幼苗生长优于浙江龙泉种源和江西信丰种源。随着遮阳强度的提高,1年生和2年生2个发育阶段,福建建瓯种源幼苗比叶面积和叶绿素含量等明显增加,叶绿素a/b值、光饱和点、暗呼吸速率和Fo值等均显著降低,表现出较高的形态和生理塑性;相同遮阳处理下福建建瓯种源幼苗总叶面积、叶绿素含量和Fv/Fm值等指标显著高于浙江龙泉种源和江西信丰种源,而叶绿素a/b值、光饱和点、光补偿点和暗呼吸速率则明显低于两种源;长期遮阳和混植状态下福建建瓯种源幼苗可通过较高的生物量分配塑性,增加根系在土壤中分布来响应邻株竞争,进而促进整株干物质的积累;各光环境下,3个木荷种源2年生幼苗Fo、Fm、Fv/Fm和Fv/Fo等叶绿素荧光参数均较1年生幼苗明显升高,但各光环境间差异不显著。[结论]不同木荷种源混交林生产力差异与其对光照的塑性反应能力有关,并随幼苗年龄而变化。     

不同年龄辣木幼苗光合特性

以温室大棚中培养的10 d、20 d、30 d的辣木(Moringa oleifera)幼苗为研究对象,测定其生长指标(根长、苗高以及最大冠幅)、生理指标(叶绿素含量、可溶性糖含量、鲜质量与干质量)以及光合指标(最大光合速率、气孔导度、水分利用效率、蒸腾速率、羧化效率以及光合日进程和光响应曲线)并进行分析。结果表明:在生长环境相同的情况下,辣木幼苗的生长指标(根长、苗高和最大冠幅)均随苗龄的增加而增加,30 d辣木幼苗根长、苗高和最大冠幅比10 d辣木幼苗的分别高出28.45%、45.73%和245.86%。辣木幼苗的生理指标中,鲜质量与干质量随苗龄的增加而增加,30 d的幼苗的鲜质量和干质量比10 d的高243.76%和427.92%;辣木幼苗的干物质比率和叶绿素含量随苗龄的增加而增加,30 d幼苗干物质比率和叶绿素含量比10 d的高6.64%和205.32%;幼苗含水率和可溶性糖含量随苗龄的增加而减少,30 d的幼苗含水率和可溶性糖含量比10 d的低6.64%和10.45%。辣木幼苗的光合指标中,在光照强度为1 500 lx时苗木的最大光合速率、气孔导度、水分利用效率以及羧化效率随苗龄的增加而增强,蒸腾速率随苗龄的增大而减小;不同苗龄的辣木幼苗光合日进程呈双峰曲线,光响应曲线随光照强度的增强呈先上升后趋于平衡的趋势。     

水分胁迫对不同种源蒙古莸光合特性与生长的影响

以6个种源的1年生蒙古莸为试验材料,采用称量控水的方法,根据种源地的情况设置充足水分、中度胁迫、重度胁迫3个水分梯度,分别维持在田间持水量的80% - 85%、45% - 50%、15% - 20%开展水分胁迫试验。通过测定不同水分梯度、不同种源的光合生理与生长指标表明:蒙古莸通过降低光合效率、蒸腾速率和最大光化学效率,减缓生长和生物量积累,提高水分利用效率和根冠比来适应水分胁迫。在水分胁迫下,蒙古莸光合能力的下降是引起其生长减缓的重要原因。从蒙古莸光合能力与生长综合考虑,内蒙古土默特左旗(NT)种源是在水分胁迫下表现最优良的种源。蒙古莸在光合活动中的气体交换,水分、CO₂、光能利用效率,光合色素及荧光特性的生理响应和生长差异,反映了不同种源蒙古莸对不同水分环境表现出的生理适应策略。     

不同种源元宝槭苗期生长及生理差异分析

比较分析了在辽西北沙地环境下培育的5个种源元宝槭1年生苗木的苗高、地径及单株生物量,叶片水势、光合气体交换参数及整株水力导度等生长和生理指标的差异。结果表明:不同种源元宝槭苗木的生长及生理指标均存在显著差异。生长量方面以辽宁四合城种源苗木最高,辽宁章古台次之,其它种源较低,主要生长指标以单株生物量在不同种源间的变异程度最高。生长表现较好的辽宁四合城和章古台种源元宝槭苗木的水分状况较好,光合气体交换能力较高,同时苗木的整株水力导度也更高。综合分析,辽宁四合城和章古台种源元宝槭在辽西北沙地环境下表现出较强的适应性,较为适宜在该地区进行推广栽培。     

南移后不同种源栓皮栎幼苗光合生理性状的比较

[目的]探讨水热条件变化后不同种源栓皮栎幼苗光合生理性状的差异,为栓皮栎优良种源的引种栽培提供理论参考。[方法]收集5个地理种源(北京平谷PG、河南内乡NX、湖北秭归ZG、江西永修YX和湖南城步CB)的栓皮栎种子,选择在其自然分布南缘以南的生境(广东鹤山,HS)下进行培育,测定不同种源栓皮栎的光合生理指标。[结果]表明:低纬度CB种源栓皮栎的潜在最大净光合速率(Pmax)显著高于中高纬的ZG和PG种源(P0.05);YX种源的表观量子效率(AQY)最高,而ZG种源的最低;NX和CB种源的叶绿素相对含量(SPAD)显著高于YX种源。PSⅡ原初光能转换效率(Fv/Fm)和PSⅡ潜在活性(Fv/F0)在各种源间均差异不显著,表明各种源栓皮栎均能较好地适应水热丰沛的新生境。同时,各种源栓皮栎在暗呼吸速率(Rd)、光饱和点(LSP)、光补偿点(LCP)、Rubisco酶最大羧化速率(Vcmax)、最大电子传递速率(Jmax)、光呼吸速率(Rp)、生长参数以及叶绿素荧光参数如电子传递速率(ETR)、光化学淬灭系数(qP)和非光化学淬灭系数(NPQ)等均差异不显著。[结论]各种源栓皮栎光合生理性状的异同与其自身遗传因素和较强的生态适应性有关。     

Improving the evaluation of multiple-dowel-type connection strength

Our study focuses on predicting the ultimate short-term load carrying capacity of timber-to-timber connections with dowel-type fasteners. The wide range of possible configurations in practice makes the resolution of these values by tests unrealistic. Moreover, different current regulations do not consider some specific failure mechanisms. In many countries, the reduction of resistance involved by this phenomenon is taken into account by considering an effective number of dowels (n_ef) smaller than the actual number of dowels (n) in the connection. However, these different regulations disagree on the values of n_ef and on other points (spacing, partial coefficient of security, formulas). These discrepancies in design rules invite the fundamental research on this topic and, therefore, new methods are sought in order to estimate the load carrying capacities of the connections. In the light of these, our approach consists of predicting the load carrying capacity with the neural network numerical tool. The results obtained by this analysis tool are satisfactory, although the model remains complex. Subsequently, we focus on the simplification of this numerical model with classical regression techniques in order to implement it in a design code.     

<Emphasis Type="Italic">Ophiostoma</Emphasis> species associated with bark beetles infesting three <Emphasis Type="Italic">Abies</Emphasis> species in Nikko,Japan

Ophiostoma species were isolated from bark beetles and Abies mariesii, A. veitchii and A. homolepis attacked by the beetles in Nikko, Tochigi, central Honshu, Japan. One to two Ophiostoma species were frequently isolated from each species of bark beetle. Ophiostoma subalpinum was the most common associate of Cryphalus montanus. Ophiostoma sp. B as well as O. subalpinum was a common fungus associated with Polygraphus proximus. Ophiostoma europhioides was isolated from Dryocoetes hectographus and D. autographus as one of the common associates. Ophiostoma sp. J and Ophiostoma sp. S were frequently isolated from D. autographus and D. striatus, respectively. These fungi seem to have specific relationships with particular bark beetles. Ophiostoma sp. B, Ophiostoma sp. J and Ophiostoma sp. S have unique morphological characteristics and appear to be new species. Five trees of A. veitchii, approximately 43 years old, were inoculated with five Ophiostoma species to assess the relative virulence of the fungi. Ophiostoma subalpinum, Ophiostoma sp. B, and O. europhioides had relatively higher virulence than the other species studied.     

Parasitic Ichneumonoidea on the horse chestnut leaf miner, Cameraria ohridella (Lepidoptera: Gracillariidae) in Slovakia

Parasitic Hymenoptera from the suprafamily Ichneumonoidea attacking the horse chestnut leafminer Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae) were studied in southwest Slovakia during 2000 and 2001. The search for such species resulted in the determination of eight ichneumonid species, Gelis agilis (Fabricius), Itoplectis alternans (Gravenhorst), I. clavicornis (Thompson), I. maculator (Fabricius), Scambus annulatus (Kiss), S. brevicornis (Gravenhorst), Zatypota percontatoria (Müller), Adelognathus sp. and a braconid Colastes braconius Haliday. The most abundant species was S. annulatus. All these species recorded are polyphagous and often facultative hyperparasitoids, except C. braconius, which departs from this norm in not being hyperparasitic. The presence of more diversified native parasitoids and hyperparasitoids from the Ichneumonoidea predicate a slow successive adaptation of the parasitoid fauna to the invasive host, Cameraria ohridella.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.     

Trees and shrubs as sources of fodder in Australia

Experience with browse plants in Australia is briefly reviewed in terms of their forage value to animals, their economic value to the landholder and their ecological contribution to landscape stability. Of the cultivated species only two have achieved any degree of commercial acceptance (Leucaena leucocephala and Chamaecytisus palmensis). Both of these are of sufficiently high forage value to be used as the sole source of feed during seasonal periods of nutritional shortage. Both are also leguminous shrubs that establish readily from seed. It is suggested that a limitation in their present use is the reliance on stands of single species which leaves these grazing systems vulnerable to disease and insects. Grazing systems so far developed for high production and persistence of cultivated species involve short periods of intense grazing followed by long periods of recovery. Similar management may be necessary in the arid and semi-arid rangelands where palatable browse species are in decline.     

Populations of adult fungus gnats and shore flies in British Columbia container nurseries as related to nursery environment,and incidence of fungi on the insects

Adult fungus gnat and shore fly populations were monitored in four container nurseries near Victoria, British Columbia. In general, populations of both insects were larger in summer than in winter. Also, both insects were more abundant in the nursery with a plastic-covered, soil floor, which favored moisture accumulation and build up of algae, liverworts and mosses, than in nurseries with other types of floors such as cement. Results of fungus isolations revealed that gnats and flies both harbor the seedling pathogens Botrytis cinerea and species of Fusarium and Phoma, plus several non-pathogenic fungi. The results are discussed in relation to nursery sanitation practices, their effects on gnat and fly populations, and some possible roles of these insects in seedling disease epidemiology.     

Insecticidal activity of certain medicinal plants

The methanol extracts of eight species of medicinal plants were tested for insecticidal activity in third instar larvae of Egyptian cottonworm (Spodoptera littoralis). All extracts showed a certain degree of larval toxicity. The extracts of Ocimum basilicum, Origanum majorana and Salvia officinalis appeared to be highly toxic. The extracts significantly affected the growth indexes [relative growth rate (RGR), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD)].     

A new norlignan from Taxodium ascendens

A new norlignan, (2R,3R,4S,5S)-2,4-bis(4-hydroxyphenyl)-3,5-dihydroxy-tetrahydropyran (1), together with 9 known compounds were isolated from the branches and leaves of Taxodium ascendens. Their structures were mainly determined on the basis of MS, IR, 1D and 2D NMR spectral evidences. Methanol extract showed inhibitory activity on carbonic anhydrase II with an IC₅₀ value of 4.27 µg/ml, acetone extract and methanol extract inhibited activity of cathepsin B with IC₅₀ values of 2.12 and 3.71 µg/ml, respectively.