Phytohormones and shoot growth in a three-generation hybrid poplar family

Hybrid vigor for secondary growth in poplar has been linked with increased gibberellin (GA) concentration in cambial tissue, but the relationship between concentrations of GAs and hybrid vigor of primary growth has not been investigated. We explored associations between concentrations of GAs, abscisic acid (ABA) and indoleacetic acid (IAA) and shoot extension in a hybrid family of Populus deltoides Bartr. ex Marsh. (Clone ILL-129) and P. trichocarpa Torr. & Gray (Clone 93-968) and two F1 and 67 F2 genotypes. Rapidly elongating subapical internodes from shoots of 4-year-old clonal saplings were selected for hormone analysis. The F1 hybrids displayed heterosis (hybrid vigor) for primary growth as a result of the complementation of dominance for increased internode length from the P. trichocarpa parent and dominance for increased diameter from the P. deltoides parent. Internodes from the faster-elongating shoots of the P. trichocarpa parent had a fourfold higher concentration of bioactive GA1 and higher concentrations of GA20, GA44, GA29 and GA8 than the P. deltoides parent. However, the two fast-growing F1 hybrids had low concentrations of all five GAs, with concentrations similar to those of the slower-elongating P. deltoides parent. Concentrations of ABA and IAA were correlated with GA concentrations and there was thus no evidence of a consistent promoting or inhibiting effect of ABA or IAA within the F1 family. These results indicate that heterosis for internode growth was not primarily regulated by hormone concentration. The segregating population of F2 hybrids was analyzed to assess the possible utility of hormone screening as a selection tool. The internodes of most of the F2 hybrids were smaller than those of their F1 parents and the larger P. trichocarpa parent. Among the F2 hybrids, mature internode length varied fourfold, and was correlated with lengths of young, subapical internodes from which hormones were analyzed. In these internodes, GA1 concentrations were negatively correlated with length (r = 0.41), diameter (0.33) and mass (0.50). Indoleacetic acid concentration was negatively correlated only with diameter (r = 0.37) and positively correlated with GA1 (r = 0.46), whereas ABA concentration was not correlated with any parameter. Thus, in the F2 population, variation in hormone concentration was not primarily responsible for the variation in shoot growth, indicating that selection for individuals with high GA concentration may not be an effective strategy for identifying vigorous hybrid genotypes.     

丹红杨等6个南方型杨树无性系物候期观察研究

笔者对潜江市林业科学研究所内丹红杨等6个表现优良的南方型杨树无性系物候期进行观测研究,分析了各无性系萌芽展叶、生长、封顶落叶、开花结实、休眠的时间以及与气温变化的关系,并得出了各无性系的物候表,为丹红杨等优良杨树无性系在江汉平原的繁育栽培提供了理论依据。     

Leaf growth characteristics of fast-growing poplar hybrids Populus trichocarpa x P. deltoides

Fast-growing hybrid poplar trees (Populus trichocarpa Torr. & A. Gray x P. deltoides Bartr. ex Marsh.) were compared with slower-growing parental types in both field and laboratory experiments to determine physiological components of leaf growth that could be closely related to biomass production. Stem volume was correlated with individual leaf area (r = 0.81) and leaf growth rate (r = 0.82). Hybrids had a greater total leaf area, not because they produced more leaves, but because they had larger leaves than either parental type. The greater leaf size of the hybrids may be explained by inheritance of larger cell number from P. deltoides and larger cell size from P. trichocarpa. Rates of enlargement of isolated leaf discs in liquid culture were approximately 50% of those observed in intact leaves of field-grown plants.     

Stomatal characteristics of riparian poplar species in a semi-arid environment

Several native poplar species meet at the margins of their natural distributions in southern Alberta, Canada. In this semi-arid area, poplars are obligate riparian species but they occupy several intergrading ecoregions. Populus deltoides Bartr. ex Marsh predominates in the warmest and driest eastern prairie ecoregions; P. balsamifera L. occupies the cooler and wetter western parkland and montane ecoregions; and P. angustifolia James and hybrids between the species occur in the intermediate grassland ecoregions. We investigated stomatal characteristics of these poplars in 51 genotypes collected across the range of ecoregions and grown in a semi-arid common garden. Stomatal length differed among genotypes within species but did not differ among species, ranging from 19 to 22 microm. Total stomatal densities (adaxial plus abaxial) differed among genotypes within species but were similar among species (290-420 stomata mm(-2)). Single-surface stomatal densities differed among species and consequently, the ratio of adaxial:abaxial stomatal density also differed, ranging from 0.94 for P. deltoides to 0.27 for P. balsamifera, with intermediate stomatal density ratios in P. angustifolia and hybrids. In a subsequent study of a subset of the same genotypes, stomatal density was correlated with stomatal conductance (r2 = 0.75) and the conductance ratios differed among species in the same manner as the stomatal density ratios. We conclude that: (1) diverse poplar genotypes respond similarly to a semi-arid environment by producing comparatively small and dense stomata; (2) differences in stomatal density underlie differences in stomatal conductance and differences among species in stomatal density ratio or conductance ratio may reflect adaptation to climatic differences among ecoregions; and (3) there is substantial variation in stomatal characteristics within and among species and hybrids in this area that could be useful for the selection and breeding of poplars adapted to different climatic conditions.     

几个杨树优良品种光合净生产力的测定

通过半叶法,测定了小黑杨、黑林1号杨、拟青杨×山海关杨、中黑防1号杨、银中杨等5个杨树优良品种的光合速率、净生产力,结果表明:几个品种光合净生产力差异明显,生长量最优的品种为拟青杨×山海关杨。     

人工林场杨木材性质与生长培育关系的研究

本文以生长在 3种长江滩地类型 (江滩、洲滩、湖滩 )、3种栽植密度 ( 3m×4m ,4m× 5m ,5m× 6m)下的3个品系速生人工林杨树木材 [欧美杨无性系 72杨 (Populus×euramericacv.I -72 58) ,美洲黑杨无性系 63杨(P .deltiodescv.I-63 51 )和 69杨 (P .deltoidescv.I-69 55) ,以下简称 72杨 ,63杨 ,69杨 ]为对象 ,深入地分析了人工林杨树木材材性与生长培育之间的关系。结果表明 :( 1 )品系对滩地杨树木材材性有较大的影响。安徽新洲洲滩和湖北黄洲江滩上生长的 63杨 ,湖南沅江湖滩上生长的 72杨纤维长度最长 ,微纤丝角最小 ,导管比量最大 ,方差分析表明 :72、63、69杨微纤丝角和主要物理力学性质差异均达显著和极显著。 ( 2 )滩地类型对72、63、69杨木材材性都有或大或小的差异。方差分析表明 :63杨、69杨微纤丝角、基本密度、抗弯强度和干缩率差异显著 ,说明 63杨和 69杨受滩地类型影响较大。 ( 3)栽植密度对 72、63、69杨木材材性的影响因材性指标的不同而不同。对 72、63、69杨来讲 ,栽植密度越大 ,微纤丝角、导管比量增大 ,纤维长度、木纤维比量、木射线比量都减小 ,基本密度、抗弯弹性模量和抗弯强度也越小。方差分析表明 ,72杨和 69杨受栽植密度影响较大 ,63杨受栽植密度影响较小     

Abscisic acid relations and the response of Populus trichocarpa stomata to leaf water potential

The role of abscisic acid (ABA) in the mediation of stomatal responses to low leaf water potential was examined with intact plants and epidermal strips of Populus trichocarpa Torr. & A. Gray. Clones of this species grown under well-watered conditions maintain a high leaf conductance when the foliage wilts. However, foliar ABA concentration in P. trichocarpa increased manyfold in response to water stress as it did also in P. deltoides Bartr. ex Marsh. and P. trichocarpa x deltoides hybrids. Application of ABA to epidermal strips appeared to cause solute leakage, however stomata of P. trichocarpa remained partially open even when the guard cells were plasmolyzed. Foliar application of ABA induced closure of stomata in young expanding leaves, but not in fully expanded foliage. Ten days after ABA application, stomata on young leaves were open at high water potential but closed at low water potential. These characteristics are discussed with respect to wilty mutants of tomato and potato, which also have stomata unresponsive to leaf wilting.     

Characterization and identification of leaf morphology of Populus deltoides Bartr.clones

Leaves are of fundamental importance to plants,representing their facility to generate power and are the sensing units of plants towards the environment.An attempt was made to characterize and compare the variations of leaf morphology of various Populus deltoides Bartr.clones by studying the winter buds and other leaf parameters of fully developed leaves.To achieve these objectives,forty-three exotic and indigenous clones of P.deltoides Bartr.were evaluated for different parameters.On the basis of various morphological characteristics the results reveal that each clone has a distinct color pattern of leaves.Different colors observed in these clones varied from light green through green to dark green.Two distinct lengths of the leaf apex were found,i.e.,short and long; as well both acuminate and acute apex types were found.Erratic distribution of serration of leaves was also found.In this study,the morphological traits of leaves provided discriminatory grounds for separating various populations of P.deltoides Bartr.clones.Winter bud studies indicate that different clones vary considerably with regard to shape,color,shape of leaf scars and exudation.     

35杨等黑杨派杨树无性系区域化试验

在江苏沿海、沿江和里下河地区10个市（县）,对35杨等8个黑杨派无性系进行了区域化试验。通过对7年生树干解析数据分析表明,品种间和试点间的产量水平都达显著或极显著差异。其中,35杨与7号杨各试点平均产量极显著高于其余品种（α=0.01）,苏杨18号产量显著高于72杨（α=0.05）;位于长江圩区的江宁试点产量显著高于其他试点（α=0.05）,金湖林场试点产量显著低于其余试点（α=0.05）。通过区域产量多重比较（邓肯法）结果得出各品种适栽地区：35杨在江苏各栽培区均速生高产,生长稳定性高,可在江苏全省广泛应用;苏杨7号丰产性显著优于69杨与72杨,在沿海轻度盐碱地和沿江平原地区适应性强,可在类似地推广;74杨和17号杨平均丰产性低于72杨和69杨,但74杨平均造林成活率高,在徐州地区表现出一定的生长优势,而17号杨分枝角度小,树干通直,高生长优势明显,是营建农田防护林和公路绿化的优良品种,因此可以控制推广。     

Thigmomorphogenesis: changes in the morphology and mechanical properties of two Populus hybrids in response to mechanical perturbation

To identify hybrid-specific differences in developmental response to mechanical perturbation (MP), we compared the effects of stem flexure on several morphological and mechanical properties of two Populus trichocarpa Torr. & A. Gray x P. deltoides Bartr. ex Marsh. hybrids, 47-174 and 11-11. In response to the MP treatment, both hybrids exhibited a significant increase in radial growth, especially in the direction of the MP (47-174, P = 0.0001; 11-11, P = 0.002), and a significant decrease in height to diameter growth ratio (P = 0.0001 for both hybrids), suggesting that MP-treated stems are more tapered than control stems. A direct consequence of the MP-induced increase in radial growth was a significant increase in flexural rigidity (EI, N mm(2)) in stems of both hybrids (47-174, P = 0.0001; 11-11, P = 0.009). Both control and MP-treated stems of Hybrid 47-174 had significantly greater height to diameter ratios and EI values than the corresponding stems of Hybrid 11-11 (11-11 stem ratios and EI values were 85 and 76%, respectively, of those of 47-174). In Hybrid 47-174, Young's modulus of elasticity (E, N mm(-2)), a measure of stem flexibility, for MP-treated stems was only 80% of the control value (P = 0.0034), whereas MP had no significant effect on E of stems of Hybrid 11-11 (P = 0.2720). Differences in flexure response between the hybrids suggest that Hybrid 47-174 can produce a stem that is more tolerant of wind-induced flexure by altering both stem allometry and material properties, whereas Hybrid 11-11 relies solely on changes in stem allometry for enhanced stability under MP conditions.