Interactions between the willow beetle Phratora vulgatissima and different genotypes of Salix viminalis

Abstract 1 Planting of species mixtures is a strategy for the non‐chemical management of willow beetles in short‐rotation coppice willows. However, the relatively susceptible Salix viminalis genotypes and their hybrids dominate current high‐yielding willows. Interactions between Phratora vulgatissima and different genotypes of S. viminalis were examined under laboratory conditions to determine if these genotypes exhibit genetic differences in susceptibility to willow beetle damage. 2 Seven S. viminalis genotypes and four hybrids were tested for the feeding preference of adult P. vulgatissima, larval performance and within‐season plant response to manual defoliation (50% and 75%). 3 The feeding preference of adult beetles, the growth rate of larvae, and the weight at 33 days of larvae and pupae differed significantly between genotypes. Genotypes also differed significantly in their height and weight responses to mechanical defoliation. Two genotypes were taller, with longer internodes, after defoliation than were undamaged plants. Two hybrids and their S. viminalis parent showed no significant reduction in final dry weight between 0% and 50% defoliation treatments. 4 Susceptibility of genotypes to adult feeding was not correlated with their tolerance to defoliation in terms of weight or height responses; however, larval growth rate on genotypes was negatively correlated both with final height and number of leaves after 75% defoliation and with the susceptibility of genotype to adult feeding. 5 Salix viminalis showed genetic differences for all parameters tested. This suggests that the planting of a mixture of these genotypes would contain genetic differences with respect to host susceptibility to P. vulgatissima. Some parameters showed similarities between a hybrid and its parent, whereas others showed differences between siblings. This offers potential for effective breeding of desirable traits.     

Effects of leaf beetle damage on stem wood production in coppicing willow

1 The effect of defoliation by larvae of the leaf beetle Phratora vulgatissima on current‐year stem wood production of resprouting Salix viminalis was investigated for two years. Adjacent subplots with varying levels of defoliation within one large willow plantation in south Sweden were studied in the two years. 2 High defoliation levels reduced stem wood production by an average of 32 and 39% in the two years, respectively. 3 Medium defoliation levels reduced stem wood production by 16% in one year. In the other year, the stem wood production of medium‐defoliated stools did not differ significantly from stools exposed to low defoliation, i.e. there was full compensatory growth. 4 The main difference between the year with compensatory growth and the one without was that overall productivity was higher in the year with compensation. This finding forms the basis for a mechanistic model by which compensation could be accomplished. We propose that the major contribution to full compensation comes from an increased growth among intermediate‐sized shoots of medium‐defoliated stools relative to the corresponding shoots in stools exposed to low defoliation.     

辽东栎幼苗对干旱和去叶的生态反应的初步研究

幼苗阶段是植物种群生活史中亏损最严重的时期之一。通过干旱处理和去叶试验研究了辽东栎幼苗的生态反应。结果表明：⑴干旱处理显著降低了单叶面积、叶面积比和叶比重,从而也降低了单株生物量,但根比重却较对照组有显著上升;⑵去叶显著提高了单株叶数、叶面积比和叶比重,尽管单株生物量只稍高于对照组,这说明辽东栎在去叶后有一定的补偿能力。     

Effects of timing of defoliation on nitrogen assimilation and associated changes in ethylene biosynthesis in mustard (<Emphasis Type=Italic>Brassica juncea</Emphasis>)

Mustard (Brassica juncea L.) is characterized by oblong-shaped leaves on the lower layers of axis. These leaves are poorly illuminated, remain below light photosynthetic compensation point and abscise at maturity. Earlier research has shown that the removal of these shaded leaves improves photosynthetic potential of the rest of the leaves, the overall growth and yield of the crop. Now we show that 50% removal of these leaves at pre-flowering stage, i.e. 40 days after sowing (DAS) enhances nitrogen assimilation in the leaves more substantially than defoliation at post-flowering stage, i.e. 60 DAS. Further, the changes in N assimilation were concurrent with the ethylene evolution. It is suggested that strategies that lead to the abscission of lower leaves at early stage of growth may be adopted for efficient N utilization, and ethylene may be considered as an important physiological tool.     

Effect of defoliation on tracheid production and the level of indole-3-acetic acid in Abies balsamea shoots

To simulate feeding by the spruce budworm ( Choristoneura fumiferana Clem.), the apical current-year shoots on 1-year-old branches in the uppermost whorl of 6-year-old balsam fir [ Abies balsamea (L.) Mill.] trees were either removed completely by debudding before the start of the growing season or defoliated 0, 50, 90 or 100% shortly after budbreak. Debudded branches were treated at the apical end with 0, 0.1 or 1.0 mg of indole-3-acetic acid (IAA) (g lanolin)⁻¹. Ninety % of the 1-year-old needles were also removed from some of the experimental branches. After ca 4 weeks of growth, the radial width of new xylem and the level of IAA were determined in the 1-year-old internode. The IAA content was measured by radioimmunoassay.
The removal or defoliation of current-year shoots inhibited tracheid production and decreased the IAA level. Exogenous IAA stimulated tracheid production and increased the IAA level in debudded branches. Current-year shoot defoliation also inhibited current-year shoot elongation. The inhibitory effect of current-year needle removal on all parameters generally increased with increasing intensity of defoliation. The removal of 1-year-old needles did not affect the IAA level or current-year shoot elongation, nor did it influence tracheid production in branches with current-year shoots. However, removal of 1-year-old needles inhibited tracheid production in debudded branches supplied with exogenous IAA. The results indicate that (1) IAA is involved in the control of tracheid production in the 1-year-old internode, (2) IAA is supplied primarily by current-year shoots, and (3) defoliation by the spruce budworm inhibits tracheid production partly by decreasing the supply of IAA.     

去叶对青杨雌雄植株生长和非结构性碳水化合物的影响

近年来,森林食叶害虫在全世界呈爆发趋势.树木的非结构性碳水化合物(NSC)如何响应叶片损失对其生长和生存至关重要.雌雄异株植物在维持森林生态系统稳定性方面扮演着重要角色.然而,目前对该类植物性别之间如何响应去叶的研究还比较少.本文以我国重要的经济和生态恢复树种青杨(Populus cathayana)为研究材料,比较了...     

模拟放牧斑块与氮素添加对半干旱草原群落植物生长的影响(英文)

放牧时,动物采食及其排泄物会影响植物的生长,但动物采食及其排泄物的空间异质性可能会影响这种效应。在位于我国北方典型农牧交错区的内蒙古多伦县,我们研究了模拟放牧斑块和施氮肥对植物生长的影响,实验采用模拟放牧采食斑块(刈割半径分别为0、10、20、40和80 cm)和土壤施氮(分别为0、5、10、20 g N/m2)两种处理,植物地上部收获后分为绿体和立枯两部分,并分析其含氮量。结果表明,刈割降低了植物的生物量(41.5％),而施氮可增加生物量(57.8％)。刈割对植物生长的抑制作用在面积最小又施肥的斑块上表现更明显。土壤施氮可以促进植物生长并且影响刈割效应。同时植物的绿-枯比随施氮水平的增加而增加,因此氮会延迟植物的衰老。以上结果表明,刈割(模拟动物采食)斑块的大小会影响草原植物的生长,土壤施氮(模拟动物尿氮)可以提高草原生态系统的初级生产力,并且影响刈割效应。     

模拟放牧斑块与氮素添加对半干旱草原群落植物生长的影响

放牧时,动物采食及其排泄物会影响植物的生长,但动物彩食及其排泄物的空间异质性可能会影响这咱效应.在位于我国北方典型农牧交错区的内蒙古多伦县,我们研究了模拟入牧斑块和施氧肥对植物生长的影响,实验采用模拟放牧采食斑块(观割半径分别0、10、20、40和8cm)和土壤施氮(分别为0、5、20Gn\m2)两种处理,植物地上部收获后分为绿体和立柯两部分,并分析其含氮量.结果表明,刈割降低了植物的生物量(40.5%),而施氮可增加生物量(57.8%)刈割交通规则植物生长的抑制作用在面积最水又施肥的斑块上表现更明显.土壤施氮可以促进杜物生长并且影响刈割效应.同时植物的绿-枯比阻碍施氮水平的增回而增回,因此氮会延迟植物的衰老.以上结果表明,刈割(模拟动物采食)斑块的大小会影响草原植物的生长,土壤施氮(模拟动物尿氮)可以提高草原生态系统的初级生产力,并影响刈割效应.     

The effects of thinning and gypsy moth defoliation on wood volume growth in oaks

Stem dissection and dendroecological methods were used to examine the effects of thinning and defoliation by gypsy moth (Lymantria dispar L.) on wood volume increment in oaks (Quercus rubra L., Q. alba L., Q. prinus L.). A model was developed to evaluate radial volume increment growth at three time periods: before defoliation, during defoliation and after defoliation, as a function of species, defoliation intensity and crown position. Volume increment during these same time periods was also compared at different stem locations. Trees were defoliated for two consecutive years and results indicated that volume loss was greater during the second year of defoliation with complete recovery taking 2–3 years after defoliation. Oaks in thinned stands had similar reductions in annual volume increment during defoliation as those in the unthinned stand. Annual volume increment demonstrated a decreasing trend from stump to base of the live crown and volume increment of the lowest log (from stump height to 1.37 m), was always higher than upper log sections, even during defoliation. Both earlywood and latewood increments were reduced during defoliation; however, latewood reductions were distributed along entire stems while earlywood reductions were greater on upper stem sections within the crown.     

Effects of a stay-green mutation on plant nitrogen relations in Lolium perenne during N starvation and after defoliation

The stay-green mutation of the nuclear gene sid results in inhibition of chlorophyll degradation during leaf senescence in grasses, reducing N remobilization from senescing leaves. Effects on growth of Lolium perenne L. were investigated during N starvation (over 18 d) and after severe defoliation, when leaf growth depends on the remobilization of internal N. Rates of dry mater production, partitioning between shoots and roots, and re-partitioning of N from shoots to roots were very similar in stay-green and normal plants under N starvation. Km and Vmax for net uptake of NH4+ were also similar for both genotypes, and Vmax increased with the duration of N deprivation. The mutation had little effect on recovery of leaf growth following severe defoliation, but stay-green plants recommenced NO3- and K+ uptake 1 d later than normal plants. Import of remobilized N into new leaves was generally similar in both lines. However, stay-green plants remobilized less N from stubble compared with normal plants. It was concluded that the sid locus stay-green mutation has no significant adverse effect on the growth of L perenne during N starvation, or recovery from severe defoliation when plants are grown under an optimal regime of NO3- supply both before and after defoliation. The absence of any effect on leaf dry matter production implies that the difference in foliar N availability attributable to this mutation has little bearing on productivity, at least in the short to medium term.     

Effect of variation in photoperiodic response on diapause induction and developmental time in the willow leaf beetle, Plagiodera versicolora

The willow leaf beetle, Plagiodera versicolora (Coleoptera: Chrysomelidae) overwinters in adult diapause. In this study, the photoperiodic responses for diapause induction and developmental time were examined in the Ishikari (Hokkaido, Japan) population of P. versicolora. All females entered reproductive diapause under short daylength (L10:D14), but 31.7% of females did not enter diapause under long daylength (L16:D8). The developmental time from oviposition to adult emergence was significantly longer at L10:D14 than that at L16:D8. Norm of reaction curves illustrated variation among families in the photoperiodic responses for diapause induction and for developmental time. ANOVA indicated significant family × photoperiod interactions in the developmental time. At L16:D8, developmental time was positively correlated with the incidence of diapause in females. This means that a female having a longer developmental time tends to have a longer critical photoperiod. Such variation may be maintained by differences in selection pressures on the growth rate and the critical photoperiod for diapause induction between univoltine and bivoltine genotypes because Ishikari is located in a transitional area between populations with univoltine and bivoltine life cycles.     

Analysis of leaf appearance,leaf death and phoma leaf spot,caused by Leptosphaeria maculans,on oilseed rape (Brassica napus) cultivars

Development of phoma leaf spot (caused by Leptosphaeria maculans) on winter oilseed rape (canola, Brassica napus) was assessed in two experiments at Rothamsted in successive years (2003–04 and 2004–05 growing seasons). Both experiments compared oilseed rape cultivars Eurol, Darmor, Canberra and Lipton, which differ in their resistance to L. maculans. Data were analysed to describe disease development in terms of increasing numbers of leaves affected over thermal time from sowing. The cultivars showed similar patterns of leaf spot development in the 2003–04 experiment when inoculum concentration was relatively low (up to 133 ascospores m⁻³ air), Darmor developing 5.3 diseased leaves per plant by 5 May 2004, Canberra 6.6, Eurol 6.8 and Lipton 7.5. Inoculum concentration was up to sevenfold greater in 2004–05, with Eurol and Darmor developing 2.4 diseased leaves per plant by 16 February 2005, whereas Lipton and Canberra developed 2.8 and 3.0 diseased leaves, respectively. Based on three defined periods of crop development, a piece-wise linear statistical model was applied to the progress of the leaf spot disease (cumulative diseased leaves) in relation to appearance (‘birth’) and death of leaves for individual plants of each cultivar. Estimates of the thermal time from sowing until appearance of the first leaf or death of the first leaf, the rate of increase in number of diseased leaves and the area under the disease progress line (AUDPL) for the first time period were made. In 2004–05, Canberra (1025 leaves ×°C days) and Lipton (879) had greater AUDPL values than Eurol (427) and Darmor (598). For Darmor and Lipton, the severity of leaf spotting could be related to the severity of stem canker at harvest. Eurol had less leaf spotting but severe stem canker, whereas Canberra had more leaf spotting but less severe canker.     

混交对亚热带针叶树根际土壤氮矿化和微生物特性的影响

混交阔叶树是退化红壤区针叶林改造的重要措施之一,土壤养分供应和转化是评价混交效应的重要参数,但混交后针叶树根际土壤氮矿化特征及其影响因素还不清楚。选取退化红壤区马尾松（Pinus massoniana Lamb.）纯林、湿地松（Pinus elliottii Engelmann）纯林及其补植木荷（Schima superba Gardn.et Champ.）形成的马-木混交林和湿-木混交林为研究对象,采集4种林分下针叶树根际土壤,测定速效养分含量、氮矿化速率、氮水解酶活性和微生物磷脂脂肪酸含量,探究混交对针叶树根际土壤氮供应及微生物特性的影响,分析土壤氮矿化和微生物特性间的相关性。结果表明：混交显著增加了针叶树根际土壤铵态氮,矿质氮和有效磷含量,而对硝态氮影响不显著。根际土壤氮矿化以硝化作用为主,混交后针叶树根际土壤氨化速率降低了27.0%,硝化速率增加了55.4%,而最终净氮矿化速率增加了24.1%。两个树种间,马尾松根际土壤矿质氮含量和净氮矿化速率显著高于湿地松。针叶树根际土壤真菌、丛枝菌根真菌,总微生物生物量及真菌/细菌比在混交后显著增加,且马尾松根际土壤总微生物和真菌生物量分别比湿地松高18.9%和27.0%。同时,针叶树根际土壤β-N-乙酰氨基葡萄糖苷酶活性在混交后显著增强,且根际土壤硝化速率和净氮矿化速率与微生物指标和酶活性正相关。总的来说,混交阔叶树显著提高了针叶树根际土壤氮供应,以此应对阔叶树混交后带来的养分竞争压力,而马尾松倾向于积极性的应对策略,通过增加土壤氮矿化以适应外界环境改变。     

Jasmonate effects on in vitro tuberization and tuber bulking in two potato cultivars (Solanum tuberosum L.) under different media and photoperiod conditions

Summary Jasmonic acid (JA) effects on in vitro tuberization of potato nodal explants cvs. Sangre and Russet Burbank were tested under liquid and solid media conditions and 0,8, and 16h photoperiod. Explants taken from stock plants grown on 2.5μM JA-supplemented medium tuberized first, particularly in darkness. The most pronounced benefits of the JA pretreatment were recorded under 16h photoperiod, which is known to inhibit tuberization. Cultivar Sangre benefited from the JA preconditioning of stock plants more than Russet Burbank. Russet Burbank required the JA supplement in tuberization media to reach the same degree of stimulation. Overall, microtubers produced either from JA preconditioned stock plants or on the JA-containing tuberization media were more uniform and larger than from other treatments. Eight hours photoperiod was by far the best treatment for the production of high-quality uniform microtubers. JA conditioning of stock plants prior to taking explants for tuberization is being proposed as a treatment enhancing the quality of microtubers.     

Bottom-up cascade in a tri-trophic system: different impacts of host-plant regeneration on performance of a willow leaf beetle and its natural enemy

Abstract.  1. Plant quality can directly and indirectly affect the third trophic level. However, little attention has been paid to how changes in plant quality affect the performance of predators through trophic levels, and which herbivores or predators are affected more strongly by host-plant quality. The present study examined the effects of artificial cutting of willows on the performance of a willow leaf beetle ( Plagiodera versicolora Laicharting) and its predatory ladybird beetle ( Aiolocaria hexaspilota Hope).
2. Laboratory experiments showed that performance (survival rate, developmental time, and adult mass) of the willow leaf beetle was higher when fed with leaves of cut willows than when fed with leaves of uncut willows. Performance (developmental time and adult mass) of the predatory ladybird was also improved when it was fed on the leaf beetle larvae that had been fed on leaves of cut willows, compared with those that had been fed on leaves of uncut willows. This indicates that a bottom-up cascade occurs in the tri-trophic system.
3. In a comparison of improved performance parameters between the leaf beetle and the ladybird, regenerated willows shortened the developmental time of the willow leaf beetle more than that of the ladybird. This indicates that the impacts of willow cutting on insect performance differ between the second and third trophic levels.     

Guidelines for measuring and reporting environmental conditions in controlled-environment studies

Guidelines for measuring and reporting environmental conditions in plant growth chambers are presented in tabular form. These guidelines are recommended by the North Central Region (NCR-101) Technical Committee on Growth Chamber Use, a committee formed under the Cooperative Research Program of the State Agricultural Experiment Stations (SAES) and the United States Department of Agriculture (USDA). Recommendations on location and frequency of measurements as well as suggested format and units of measurement are listed for each environmental parameter. The adoption of these standardized guidelines should greatly improve the uniformity of research conducted in controlled environments and facilitate comparison of experimental results obtained in studies conducted in different laboratories on a world-wide basis.