Genetic variation in foliar nutrient concentration in relation to foliar carbon isotope composition and tree growth with clones of the F1 hybrid between slash pine and Caribbean pine

The objectives of this study were: (1) to quantify the genetic variation in foliar nutrient concentration in relation to foliar carbon isotope composition (δ¹³C) and tree growth of 122 clones of ca. 4-year-old F₁ hybrids between slash pine (Pinus elliottii Engelm var. elliottii) and Caribbean pine (P. caribaea var. hondurensis Barr. et Golf.) grown at two experimental sites with different water and nutrient availability in southeast Queensland, Australia and (2) to examine the potential of using foliar nutrient concentration of the 4-year-old tree canopies for selecting elite F₁ hybrid pine clones with improved nutrient-use efficiency (NUE) and water-use efficiency (WUE), and ultimately enhanced tree growth under ambient growing conditions. There were significant differences in foliar nutrient concentrations between two canopy positions (upper outer and lower outer canopy) sampled, between summer and winter, and between the two sites. This highlights that foliar nutrient concentrations are influenced by sampling and environment. Significant genetic variations in foliar nutrient concentrations were detected between the clones, between the female parents, and between the male parents of the clones in both sampling seasons at both sites. Depending on the nutrient concerned, canopy position, season, and site sampled, the clones accounted for 4.7–33.9% of the total variation in foliar nutrient concentrations, the clone female parents for 0–25.1% and the clone male parents for 0–28.6%. The site-by-clone interactions were statistically significant for foliar N, P, Mg, Cu, Zn, Mn, Fe and mineral concentrations at the upper outer canopy in summer, and for foliar N concentration in winter. There were significant, positive correlations between clone means of foliar δ¹³C and N concentration at the upper outer canopy in summer for the wet site, while clone foliar δ¹³C was also positively related to clone foliar N concentration at both canopy positions in summer for the dry site. This suggests that clone WUE as reflected in foliar δ¹³C may be improved by selecting elite clones with higher foliar N concentration and increased photosynthesis, leading to enhanced tree growth when both water and N are the major growth-limiting factors. This is supported by the positive correlation detected between clone tree height and foliar N concentration at the upper outer canopy for both sites. Thus, foliar nutrient (particularly N) concentration, together with foliar δ¹³C, may be useful for assisting in selection of exotic pine clones with improved NUE and WUE, and enhanced tree growth under the nutrient- and water-limiting environments.     

Partititioning concurrent influences of nitrogen and phosphorus supply on photosynthetic model parameters of Pinus radiata

Responses of photosynthesis (A) to intercellular CO(2) concentration (C(i)) were measured in a fast- and a slow-growing clone of Pinus radiata D. Don cultivated in a greenhouse with a factorial combination of nitrogen and phosphorus supply. Stomatal limitations scaled with nitrogen and phosphorus supply as a fixed proportion of the light-saturated photosynthetic rate (18.5%) independent of clone. Photosynthetic rates at ambient CO(2) concentration were mainly in the V(cmax)-limited portion of the CO(2) response curve at low-nitrogen supply and at the transition between V(cmax) and J(max) at high-nitrogen supply. Nutrient limitations to photosynthesis were partitioned based on the ratio of foliage nitrogen to phosphorus expressed on a leaf area basis (N(a)/P(a)), by minimizing the mean square error of segmented linear models relating photosynthetic parameters (V(cmax), J(max), T(p)) to foliar nitrogen and phosphorus concentrations. A value of N(a)/P(a) equal to 23 (mole basis) was identified as the threshold separating nitrogen (N(a)/P(a) < or = 23) from phosphorus (N(a)/P(a) > 23) limitations independent of clones. On an area basis, there were significant positive linear relationships between the parameters, V(cmax), J(max), T(p) and N(a) and P(a), but only the relationships between T(p) and N(a) and P(a) differed significantly between clones. These findings suggest that, in genotypes with contrasting growth, the responses of V(cmax) and J(max) to nutrient limitation are equivalent. The relationships between the parameters V(cmax), J(max), T(p) and foliage nutrient concentration on a mass basis were unaffected by clone, because the slow-growing clone had a significantly greater leaf area to mass ratio than the fast-growing clone. These results may be useful in discriminating nitrogen-limited photosynthesis from phosphorus-limited photosynthesis.     

抗病和感病泡桐无性系组培苗对嫁接传染植原体的不同反应

用感染了植原体并表现典型丛枝症状的组培苗作接穗或砧木，在无杂菌条件下嫁接７个表现不同田间抗性的无性系健康组培苗，并用ＤＡＰＩ荧光显微镜和１６ＳｒＲＮＡ基因扩增（ＰＣＲ）技术检验嫁接传病效果。Ｃ１２５和ＸｕＨ表现出较强的特异性接种诱发坏死反应，ＺＨ和Ｔ３５０２８坏死反应中等，ＱＬＭ、Ｃ０２０和Ｃ１６１的坏死反应较弱。培养基中添加植物生长调节剂（６ＢＡ或ＮＡＡ）可降低坏死程度，提高嫁接成功率，水杨酸处理或去掉健株砧木叶片和根系皆加重坏死反应程度。用病接穗嫁接抗病的ＱＬＭ无性系时，用ＰＣＲ检测到侵染砧木的植原体，但未表现丛枝症状，而将此无性系健康接穗嫁接到丛枝病砧木上时可诱致典型丛枝症状，从而表现出与根系和成熟叶相关的抗性反应。除Ｃ１２５外，其余６个无性系皆被嫁接传染，其继代培养表现出差异不显著的丛枝症状，其韧皮部金黄色自发荧光随着症状的加重而累积，也与抗病性有一定的联系。     

Rootstock effects in grafted conifers: A review

The literature on rootstock effects (on scions) in conifers was reviewed, specifically: graft success, compatibility, size, reproduction, phenology, crown and needle characters, mineral contents, organic compounds, water relations, disease resistance and wood properties. Scions usually had higher graft success and less incompatibility on more closely related rootstocks although there were exceptions. Even intergeneric grafts have succeeded on occasion. Although there were marked rootstock effects on growth and reproduction, the effects did not follow a pattern with increasing relationship. It is also likely that some crown characters and the nutrient content of scions can be manipulated by the use of rootstocks. For many characters, a specific rootstock may give a desired result only for a limited number of scion types (species, cultivars or clones). With some exceptions, the review shows that the subject has not been comprehensively studied. Many of the studies were either short-term, inadequately replicated, or poorly designed to allow firm conclusions about rootstock effects. The physiological and biochemical mechanisms, which cause the changes seen in morphology, are not well understood. Further research and more comprehensive study of rootstock effects on scion biology are recommended.     

Evidence for increased sensitivity to nutrient and water stress in a fast-growing hybrid willow compared with a natural willow clone

The hypothesis that fast-growing breeds of willow (Salix spp.) are more sensitive to nutrient and water stress and less efficient in nutrient- and water-use than slower-growing natural willow clones was tested. Cuttings of a natural clone of S. viminalis L. collected in Sweden (L78183) and a hybrid clone of S. schwerinii E. Wolf. x S. viminalis L. ("Tora") were grown outdoors in pots under various experimental conditions in a full-factorial design. The experimental conditions included three fertilization, two irrigation and two temperature regimes. Classical growth analysis techniques, based on an initial and a final harvest, were used as a screening method, together with calculation of intrinsic water-use efficiency (foliar carbon isotope ratio; delta13C). In addition, nitrogen-use efficiency was calculated as the product of nitrogen productivity and mean residence time of nitrogen on an annual basis. There were significant differences in plant structural parameters (leaf area ratio, specific leaf area) and water-use efficiency between the clones. Furthermore, several clone x treatment interaction effects on various growth parameters indicated that the clones adapted to specific environments in different ways. "Tora" plants produced up to 25% more shoot biomass than plants of the natural clone in response to high rates of fertilization and irrigation, whereas clone ranking was reversed in most other treatments. The results support the hypothesis that fast-growing hybrids are more sensitive to nutrient and water stress than slower-growing natural clones. The hypothesis that natural clones have higher resource-use efficiency than fast-growing hybrids was supported with respect to water, but not nitrogen.     

Inter-specific variation in foliar nutritional responses to disturbance by small coupe harvesting varies with landscape position

The effects of small coupe harvesting on the foliar nutritional characteristics of four indigenous plant species were investigated in a New Zealand Nothofagus truncata forest. The coupes were established in 1994, and installed in replicated logged and unlogged pairs of plots on the ridge line, face and gully of a valley, allowing variation with landscape position to be assessed. Foliar sampling occurred in March 2006. Logging significantly increased foliar nitrogen and phosphorous concentrations. Logging increased foliar δ¹⁵nitrogen, attributed to increased rates of mineralisation and nitrification, and decreased nutrient demand. Foliar calcium, magnesium and strontium concentrations were significantly decreased by logging, and this was considered the result of increased leaching in the logged coupes. The effect of the harvest treatment varied considerably with plant species, and it was determined that the examination of multiple plant species is critical to accurately assessing the effect of logging on nutrient availability. Foliar nitrogen, calcium and strontium concentrations decreased significantly from ridge line to gully coupes, and this was attributed to water movement. The effect of logging on foliar calcium and strontium concentrations also varied significantly with landscape position. It was concluded that small coupe harvesting in N. truncata forests causes substantial long term disturbances to nutrient dynamics, which may alter the relative diversity of the regenerating plants in the coupes.     

Effects of soil water content and initial root volume on the nutrient status of 2+0 Douglas-fir seedlings

Two-year-old bareroot Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco.) seedlings were graded on the basis of four root-volume categories and transplanted to four moisture-stress treatments (6, 12, 18, and 24% soil water content) in pots. Macronutrient concentrations and contents of both old and new foliar tissue were determined. Decreasing soil water content resulted in higher concentrations of phosphorus, potassium, and particularly nitrogen in both old and new foliar tissue. This can be attributed to reduced growth, translocation, metabolic activity, and nutrient requirement in response to moisture stress. Seedlings with relatively higher root volumes exhibited higher nutrient concentrations and contents, as well as increased growth. Thus, increased total root biomass per unit of soil area with increasing seedling root volume may have resulted in greater nutrient use, supply, uptake, and storage.     

半枫荷塑料大棚内嫁接快速育苗技术研究

对半枫荷塑料大棚内嫁接育苗试验的结果表明,当年用休眠芽嫁接,翌年6月嫁接成活率可达95.07%,平均接穗高67.33 cm,平均接穗茎粗0.54 cm。砧木以3年生半枫荷I级侧枝为好,嫁接成活率、生长量、保存率由高到低排序为容器苗>移植苗>留床苗,砧木切干高度对成活率和生长量无影响。     

Factors influencing in vivo and in vitro micrografting of sandalwood (Santalum album L.): an endangered tree species

In vivo micrografting of Santalum album was achieved (50%) by grafting 4- to 5-cm-long scions, collected from a candidate plus tree (CPT) of 50–60 years of age, onto 90-day-old nursery-grown rootstock. Scion size, rootstock age, and scion collection season were found to influence graft success. Grafted plants were incubated under greenhouse conditions for 6–8 weeks during the graft union process. In vitro micrografts were achieved by placing 1- to 2-cm-long scions derived from nodal shoot segments (collected from CPT) onto the hypocotyl of 45-day-old in vitro rootstocks. Use of in vitro grown shoots as a source of scion gave better graft success (60%) than scions collected directly from field-grown trees. In vitro grafting was also influenced by scion size and rootstock age. Under favorable conditions, scions and hypocotyls unite to form complete plants that produced two to four leaves after 6–8 weeks. This is the first report on in vivo and in vitro micrografting of S. album having potential for production of disease-free clonal plants for conservation and improvement targets.     

GLS系列油茶优良无性系繁育技术

GLS系列油茶优良无性系是赣州市林业科学研究所通过多年系统选择产生的优良品种。为了加快GLS高产油茶的繁殖速度,结合实践总结出采用GLS油茶枝条作接穗,利用芽苗砧嫁接技术进行育苗,培育出优质的GLS油茶优良无性系苗。     

Open-pollinated, interspecific F1 hybrid seed orchards of Leucaena: I. Rootstock effects

Seed orchards of Leucaena were established at two experimental sites in Hawaii to produce either triploid or tetraploid interspecific hybrid seed by interplanting clonal self incompatible diploid (L. diversifolia, L. esculenta) or tetraploid (L. pallida) species with self- compatible L. leucocephala lines and the F1 hybrid of L. diversifolia (2n = 4x) × L. leucocephala. The seed parents were grafted onto three seedling rootstocks (L. diversifolia (2n = 4x), shrubby L. leucocephala, and giant L. leucocephala) to compare rootstock effects on scion growth. This paper reports on the effects of rootstock on scion growth during the first year based on total truck cross sectional area, height growth, and crown habit. In the triploid seed orchard, rootstock significantly affected the growth of four of the six clones, while in the tetraploid orchard the growth of two of the five clones was significantly affected by rootstock. Crown habit was independent of rootstock. Our study suggests that rootstock effects depend on the specific scion and rootstock combination, and site. This revised version was published online in June 2006 with corrections to the Cover Date.     

不同林龄樟子松叶片养分含量及其再吸收效率

树木叶片的养分再吸收效率能够反映树木对养分保存、利用以及对养分贫瘠环境的适应能力。以科尔沁沙地东南缘章古台地区樟子松人工林为研究对象,分析了11、20、29、45年生树木叶片的基本特征、养分含量及其再吸收效率。结果表明:叶片衰老后其质量和面积明显减少;叶片凋落前的平均养分含量没有表现出随樟子松年龄增加而出现有规律的变化;凋落叶片中的N、P、K、Mg含量表现出随年龄增加而增加的趋势,而Ca的趋势与之相反;11年生和20年生的樟子松叶片N、P、K的再吸收效率相似,都显著高于29年生和45年生樟子松(P<0.05),而樟子松叶片对Mg的再吸收效率表现出随年龄增大而显著降低,Ca随叶片的衰老而不断累积,再吸收效率表现为负值,20年生的樟子松叶片Ca再吸收效率最大,11年生和45年生最低。樟子松叶片的N、P、K、Mg养分再吸收效率随年龄增加而降低的趋势表明,随年龄增加樟子松对贫瘠养分生境的适应能力逐渐降低,反映了樟子松养分保存方面的衰退特征。     

旱柳无性系在富营养化水体中的生长及去除氮磷能力

【目的】比较旱柳无性系的生长以及对水体中氮、磷去除效果,以筛选出处理富营养化水体效果较好的无性系。【方法】利用8个旱柳无性系在富营养化水体中进行静态培养试验,研究各无性系的形态特征、叶绿素相对含量指数、对营养元素的吸收以及对废水中氮、磷的去除效率。【结果】旱柳无性系在整个试验期间生长良好,无死亡现象。各无性系最终生物量、苗高和相对生长率有显著差异,其中,旱59和旱97整体表现最好。旱柳无性系对富营养化水体中氮、磷吸收较好,地上部分营养元素浓度较高。旱柳各无性系对总氮、氨氮和硝态氮的去除效率分别为87.17%96.94%、90.35%99.33%和66.66%88.19%,对总磷的去除效率为76.59%83.15%,无性系旱13总的去除效率最高。【结论】参试8个旱柳无性系均能在富营养化水体中正常生长,但各无性系在富营养化水体中的生长响应有较大差异。综合多个指标并结合长期野外试验观察,旱13、旱59、旱97是适合修复富营养化水体的较好材料。     

低磷胁迫下不同杉木家系根系H^+流动态变化

通过分析不同杉木家系在不同供磷处理下根系H^+流变化规律,探讨根系H^+流与杉木适应低磷胁迫调控的关系,为揭示磷高效利用杉木适应低磷胁迫的内在机制提供科学依据。以前期筛选出的不同磷利用效率杉木家系M28与M32为研究对象,通过设计3个供磷处理[正常供磷(H-P),31 mg·L^-1;中度缺磷(L-P),16 mg·L^-1;重度缺磷(N-P),0 mg·L^-1]和3个时间处理梯度(3、8、15 d)室内水培试验,并利用非损伤微测技术(NMT)分别测定两个家系在不同供磷处理和不同时间处理梯度下完整根系及不同部位的H^+动态变化规律。结果表明:不同杉木家系完整根系H^+全程表现为内流,但二者H^+流变化存在显著差异,M28完整根系H^+吸收表现为8 d>15 d>3 d,M32在不同时间处理下H^+的变化无显著差异(P>0.05)。结合根系不同部位H^+流向分析可得,M28与M32仅在L-P和N-P处理3 d时表现出少量H^+外排现象,其中M28对外界磷环境的感应比M32更为敏感,在L-P处理下就发生H^+外排现象,M32在N-P处理才发现H^+外排。随着时间推移,在处理8、15 d后,两个杉木家系均未观测到H^+的外排,可见低磷胁迫下根系H^+外排是一种应激反应。不同杉木家系根系H^+流在低磷环境下表现出不同的适应性变化,其中M28根系的H^+流对外界磷环境的改变更为敏感。     

Photosynthetic capacity and foliar nitrogen distribution in Eucalyptus nitens is altered by high-intensity thinning

The changes in photosynthetic rates, light environment and foliar nutrient concentrations following thinning were examined in an 8-year-old Eucalyptus nitens (Deane and Maiden) Maiden plantation. The objectives of the study were to: (1) determine the extent to which maximum photosynthetic rates (Amax) of E. nitens are affected by stand thinning; (2) relate the spatial pattern of Amax within the crown to the changes in light environment caused by thinning; and (3) establish if the responses of Amax to thinning are driven by changes in area-based foliar nitrogen (Na) or phosphorus (Pa) concentrations. Photosynthetic rates measured under saturating light availability increased throughout the crown after thinning. The greatest increases were observed in the lower and middle crown zones. Photosynthetic rate was positively related to foliar N concentration. Thinning increased Na and Pa because of a significant decrease in specific leaf area (SLA) after thinning. Changes in photosynthetic rates, SLA and foliar nutrient distributions with thinning were well correlated with changes in incident solar irradiance throughout the tree crown.     

Relationship Between Height Growth and Foliar Nutrient N and P Concentration in a Eucalyptus grandis Plantation in Northeastern Argentina

The relationship between the height growth, foliar concentrations of nitrogen (N) and phosphorus (P), and the N:P ratio was analyzed in a fourth rotation plantation that did not respond to fertilization with these nutrients. Spearman's nonparametric correlation analysis was used to evaluate the association between growth in height—calculated as the difference between heights measured at 1 yr and 2 yr after planting—and foliar N and P concentrations, as well as N:P ratio, determined in the 1-yr-old plantation. Only a weak positive correlation between height growth and foliar P concentration in planted seedlings was found. A significant negative relation was observed between the growth and N:P ratio in seedlings. Foliar concentrations suggest that there were neither P nor N limitations for growth in the analyzed period. This may be due to the management of harvest residues, which were abandoned on-site without burning.     

Hydraulic conductance characteristics of peach (Prunus persica) trees on different rootstocks are related to biomass production and distribution

We investigated hydraulic conductance characteristics and associated dry matter production and distribution of peach trees grafted on different rootstocks growing in the field. A single scion genotype was grown on a low ('K146-43'), an intermediate ('Hiawatha') and a high ('Nemaguard') vigor rootstock. 'K146-43' and 'Hiawatha' rootstocks had 27 and 52% lower mean leaf-specific hydraulic conductances, respectively, than the more vigorous 'Nemaguard' rootstock. Tree growth rates and patterns of biomass distribution varied significantly among rootstocks. Mean dry mass relative growth rates of trees on 'K146-43' and 'Nemaguard' were 66 and 75%, respectively, of the rates of trees on 'Nemaguard', and the scion to rootstock dry mass ratios of trees on 'K146-43' and 'Hiawatha' were 63 and 82%, respectively, of the ratio of trees on 'Nemaguard'. Thus, differences in dry matter distribution between the scion and rootstock, which may be a compensatory response to the differences in leaf specific hydraulic conductance among rootstocks, appeared to be related to differences in growth rates. Correspondingly, there was a positive linear relationship between the scion to rootstock dry mass ratio and the rootstock to scion hydraulic conductance ratio when conductance was normalized for dry mass. This study confirms that rootstock effects on tree water relations and vegetative growth potential result, at least in part, from differences in tree hydraulic conductance associated with specific peach rootstocks.     

Genetic effects on total phenolics, condensed tannins and non-structural carbohydrates in loblolly pine (Pinus taeda L.) needles

Carbon allocation to soluble phenolics (total phenolics, proanthocyanidins (PA)) and total non-structural carbohydrates (TNC; starch and soluble sugars) in needles of widely planted, highly productive loblolly pine (Pinus taeda L.) genotypes could impact stand resistance to herbivory, and biogeochemical cycling in the southeastern USA. However, genetic and growth-related effects on loblolly pine needle chemistry are not well characterized. Therefore, we investigated genetic and growth-related effects on foliar concentrations of total phenolics, PA and TNC in two different field studies. The first study contained nine different genotypes representing a range of genetic homogeneity, growing in a 2-year-old plantation on the coastal plain of North Carolina (NC), USA. The second study contained eight clones with different growth potentials planted in a 9-year-old clonal trial replicated at two sites (Georgia (GA) and South Carolina (SC), USA). In the first study (NC), we found no genetic effects on total phenolics, PA and TNC, and there was no relationship between genotype size and foliar biochemistry. In the second study, there were no differences in height growth between sites, but the SC site showed greater diameter (diameter at breast height (DBH)) and volume, most likely due to greater tree mortality (lower stocking) which reduced competition for resources and increased growth of remaining trees. We found a significant site?×?clone effect for total phenolics with lower productivity clones showing 27-30% higher total phenolic concentrations at the GA site where DBH and volume were lower. In contrast to the predictions of growth-defense theory, clone volume was positively associated with total phenolic concentrations at the higher volume SC site, and PA concentrations at the lower volume GA site. Overall, we found no evidence of a trade-off between genotype size and defense, and genetic potential for improved growth may include increased allocation to some secondary metabolites. These results imply that deployment of more productive loblolly pine genotypes will not reduce stand resistance to herbivory, but increased production of total phenolics and PA associated with higher genotype growth potential could reduce litter decomposition rates and therefore, nutrient availability.     

Foliar nutrient retranslocation in Eucalyptus globulus

We measured patterns of change in concentrations and contents of nitrogen, phosphorus, potassium, magnesium and calcium in fully expanded leaves of young Eucalyptus globulus (Labill.) trees growing in a plantation in southeastern Australia, over a 12-month period beginning at the onset of spring. There was significant net retranslocation of mobile nutrients on a seasonal basis from green leaves, coinciding with continued growth and production of foliage. There was a close positive relationship between initial nutrient content (N, P and K) of the leaf and amount retranslocated, and a tight coupling between N and P retranslocated from leaves. Net retranslocation was significantly correlated with basal area growth increments. Artificial shading of leaves resulted in senescence and reduction in leaf mass. It also induced retranslocation of N, P and K from leaves of different ages and from different position in the canopy. Although the mechanisms underlying the effects of shading intensity on these changes were not elucidated, shading provided an experimental tool for studying retranslocation. Comparison of the results with published data for Pinus radiata (D. Don) grown in the same environment indicated a similarity between the species in patterns of change in foliar nutrient contents and in factors governing foliar nutrient retranslocation, giving rise to unifying principles.     

The effects of scion maturation on growth and reproduction of grafted slash pine

Establishment of the University of Florida Cooperative Forest Genetics Research Program's clone banks provided an opportunity to look at scion maturation effects on growth and reproduction of many grafted slash pine clones. In 1988 and 1989, clone banks were established in nine locations in the Southeastern United States. Over 460 scion clones varying from 5 to greater than 40 years old from time of seed germination (chronological age) were grafted into the clone banks. Comparisons of diameter growth, height growth, lateral branch number and female and male strobili production were made annually for six years after grafting.Within slash pine clone banks, there were significant effects due to scion chronological age. Chronologically older scions (backward selections) grew less, had fewer branches and produced only a few more female strobili than chronologically younger material (forward selections). Forward selections produced significantly more catkin clusters than backward selections. By year six, there was no significant difference in numbers of female strobili per tree between backward and forward scions, but forward selections produced about 2.5 times as many catkin clusters as the backward selections. Similar effects on growth and reproduction due to chronological age were also found among clones within the forward selections, with older selections growing more slowly and producing fewer catkin clusters. The size and breadth of this study lends strong support to the idea that these patterns of growth will occur for grafted slash pine in any location throughout its native range.