Effects of thinning on the understory light environment of different stands and the photosynthetic performance and growth of the reforestation species Phoebe bournei

Light levels determine regeneration in stands and a key concern is how to regulate the light environment of different stand types to the requirements of the understory.In this study,we selected three stands typical in south China(a Cryptomeria japonica plantation,a Quercus acutissima plantation,and a mixed stand of both)and three thinning intensities to determine the best understory light environ-ment for 3-year-old Phoebe bournei seedlings.The canopy structure,understory light environment,and photosynthe-sis and growth indicators were assessed following thin-ning.Thinning improved canopy structure and understory light availability of each stand;species composition was the reason for differences in the understory light environ-ment.Under the same thinning intensity,the mixed stand had the greatest light radiation and most balanced spectral composition.P.bournei photosynthesis and growth were closely related to the light environment;all three stands required heavy thinning to create an effective and sustained understory light environment.In a suitable understory light environment,the efficiency of light interception,absorption,and use by seedlings was enhanced,resulting in a higher carbon assimilation the main limiting factor was stomatal conductance.As a shade-avoidance signal,red/far-red radia-tion is a critical factor driving changes in photosynthesis and growth of P.bournei seedlings,and a reduction increased light absorption and use capacity and height:diameter ratios.The growth advantage transformed from diameter to height,enabling seedlings to access more light.Our findings suggest that the regeneration of shade-tolerant species such as P.bournei could be enhanced if a targeted approach to thinning based on stand type was adopted.

Genome wide investigation of Hsf gene family in Phoebe bournei:identification,evolution,and expression after abiotic stresses

Heat shock transcription factors(Hsfs)have important roles during plant growth and development and responses to abiotic stresses.The identification and func-tion of Hsf genes have been thoroughly studied in various herbaceous plant species,but not woody species,especially Phoebe bournei,an endangered,unique species in China.In this study,17 members of the Hsf gene family were identi-fied from P.bournei using bioinformatic methods.Phyloge-netic analysis indicated that PbHsf genes were grouped into three subfamilies:A,B,and C.Conserved motifs,three-dimensional structure,and physicochemical properties of the PbHsf proteins were also analyzed.The structure of the PbHsf genes varied in the number of exons and introns.Pre-diction of cis-acting elements in the promoter region indi-cated that PbHsf genes are likely involved in responses to plant hormones and stresses.A collinearity analysis dem-onstrated that expansions of the PbHsf gene family mainly take place via segmental duplication.The expression levels of PbHsf genes varied across different plant tissues.On the basis of the expression profiles of five representative PbHsf genes during heat,cold,salt,and drought stress,PbHsf pro-teins seem to have multiple functions depending on the type of abiotic stress.This systematic,genome-wide investigation of PbHsf genes in P.bournei and their expression patterns provides valuable insights and information for further func-tional dissection of Hsf proteins in this endangered,unique species.

Effects of Shading Degree on Storage Rate and Growth of Phoebe bournei Seedlings in Fields

In the research, four shading treatments were set, including the treatments with shading degrees at 0, 40%, 60% and 70%, in order to explore storage rate and seedling growth of annual Phoebe bournei. The results showed that the storage rate is growing upon shading degree. In the research, for example, storage rate reached the peak with the shading degree at 70%, and only 42.2% with shading degree at 0. In addition, seedling height and ground diameter showed extremely significant differences among treatments, and the treatment with shading degree at 60% was the best.

Growth Performance of Phoebe bournei Generations in Seedling Stage

[Objective] The aim was to explore growth performance of Phoebe bournei in seedling stage.[Method] Based on 17 superior plus trees of Phoebe bournei,a seedling cultivation test was conducted in Jindong Forest Farm in Yongzhou,Hunan Province,exploring growth indices and analyzing seedling height and ground diameter.[Result] As per the selection rate at 20％,PB17,PB9 and PB12 were selected from the 17 species.Specifically,the seedling height averaged 36.52 cm of the selected three seedlings,which was higher by 16.1％ compared with average of 17 species （31.45％）.As for ground diameter,the selected species averaged 2.6 mm,which was higher （13.0％） compared with the average level （2.3 mm）.[Conclusion]Both of seedling height and ground diameter reached extremely significant differences,which indicated that half-sib families of Phoebe bournei have rich variations,with selection and breeding potential.

Phenotypic variation in Phoebe bournei populations preserved in the primary distribution area

Phoebe bournei（Hemsl.） Yang is a rare and protected plant in China. This study was conducted to determine the phenotypic variation in this species and to document phenotypic variation within and among populations of P. bournei. Nested analysis of variance, coefficient of variation, multiple comparisons, principal component analysis（PCA） and correlation analysis were used to analyze ten phenotypic traits in ten natural populations of P.bournei from both the northeastern and the primary region of the range of this species. Significant differences among and within populations were observed in leaf and seed phenotypic traits. Variation among populations（34.92%）was greater than that within populations（26.19%）. The mean phenotypic differentiation coefficient was 53.77% among populations, indicating that variation among populations comprised the majority of the phenotypic variation of P. bournei. The coefficient of variance（CV） of ten traits varied from 6.44 to 18.45%, with an average of 12.03%.The CV of leaf traits among populations（15.64%） was higher than that of seed traits（8.60%）, indicating that seed traits were more stable. The results from CV and PCA indicated that leaf area, leaf length and thousand seed weight were the main factors accounting for the observed phenotypic variations. Significant or highly significant correlations were observed among most leaf and/or in seed phenotypic traits, whereas no significant correlations were observed between phenotypic traits and geographic factors.Based on cluster analysis, the ten populations can be divided into three clusters. These clusters were not a result of geographic distances.

Study on the Structural Characteristics and Physical and Mechanical Properties of Phoebe bournei Thinning Wood

The artificial afforestation of precious Phoebe bournei has been carried out in China.During the cultivation process,thinning wood will be produced.The properties of thinning wood might vary greatly with matured wood and require evaluation for better utilization.The objective of the present study aims to determine the wood structure,fiber morphology,and physical and mechanical properties of the Phoebe bournei thinning wood to help us understand the wood properties and improve its utility value.Three 14-year-old Phoebe bournei were cut from Jindong Forestry Farm of Hunan Province,China.The wood structure and fiber morphology were observed and analyzed with a light microscope and scanning electron microscope.The physical and mechanical properties were tested according to the Chinese national standards.The results showed as follows:(1)The Phoebe bournei thinning wood has a beautiful wood figure and fine texture,whereas the heartwood has not yet formed.(2)It is a diffuse-porous hardwood with small and less pores as well as fine wood rays.(3)The wood fiber is medium length and extremely thin wall thickness.(4)It is low in density and has excellent dimensionally stability.(5)The wood mechanical properties belong to the low to medium class and the comprehensive strength of wood belongs to the medium-strength class.It is concluded that Phoebe bournei thinning wood is suitable for wood carving,handicraft,high-end furniture,and decorative furniture parts.

Comparision of the Leaf Morphology of Two Phoebe bournei Varieties

To study the leaf variation and morphological diversity of Phoebe bournei,the leaves of two leaf types and one wild type in the same growth environment,which were marked as Type A,B,and C with wild type being marked as B,were used as testing materials.40 healthy mature leaves collected from healthy plants were taken as research samples and phenotypic characteristics,such as leaf shape,leaf length,leaf width,leaf area,and leaf vein were observed and analyzed.The leaves of Type A were oblanceolate,the base of the leaves was gradually narrow,and the tip of the leaves was gradually sharp.There were white pubescences on the back of the leaves,which were arranged in order.The pubescences were evenly distributed on the mesophyll and vein,in the same direction.The length,width,perimeter,and area of the leaves were smaller than those of the other two types.The leaves of Type B were narrow,oblanceolate,wedge-shaped at the base,long acuminate at the tip,with yellow brown villi on the back of the leaves,mainly distributed along the vein and the grid vein between the veins;the villi on the main veins were longer,and the villi between the mesophylls were less numerous and shorter.The length,perimeter,and aspect ratio of the blade were the largest of the three types and the whole blade was slender.Type C leaves were elliptical with a nearly truncated base and a sharp tip.There were white pubescences on the back of the leaves and less mesophyll pubescence along the veins.The length-width ratio of the blade was small,the width was large,and the whole blade was round.There were significant differences among the three leaf types of P.bournei and preliminary judgement was that Type A and Type C were spontaneous mutants.

The chromosome-scale genome of Phoebe bournei reveals contrasting fates of terpene synthase (TPS)-a and TPS-b subfamilies

Terpenoids,including aromatic volatile monoterpenoids and sesquiterpenoids,function in defense against pathogens and herbivores.Phoebe trees are remarkable for their scented wood and decay resistance.Unlike other Lauraceae species investigated to date,Phoebe species predominantly accumulate sesquiterpenoids instead of monoterpenoids.Limited genomic data restrict the elucidation of terpenoid variation and functions.Here,we present a chromosome-scale genome assembly of a Lauraceae tree,Phoebe bournei,and identify 72 full-length terpene synthase(TPS)genes.Genome-level comparison shows pervasive lineage-specific duplication and contraction of TPS subfamilies,which have contributed to the extreme terpenoid variation within Lauraceae species.Although the TPS-a and TPS-b subfamilies were both expanded via tandem duplication in P.bournei,more TPS-a copies were retained and constitutively expressed,whereas more TPS-b copies were lost.The TPS-a genes on chromosome 8 functionally diverged to synthesize eight highly accumulated sesquiterpenes in P.bournei.The essential oil of P.bournei and its main component,b-caryophyllene,exhibited antifungal activities against the three most widespread canker pathogens of trees.The TPS-a and TPS-b subfamilies have experienced contrasting fates over the evolution of P.bournei.The abundant sesquiterpenoids produced by TPS-a proteins contribute to the excellent pathogen resistance of P.bournei trees.Overall,this study sheds light on the evolution and adaptation of terpenoids in Lauraceae and provides valuable resources for boosting plant immunity against pathogens in various trees and crops.

闽楠幼林黄化植株与正常植株表型特征的差异分析

以福建三明市将乐县闽楠(Phoebe bournei)种质保存林内发现的一株黄化植株为研究对象,并以相邻的3株正常植株为对照,通过野外调查和室内测定,分析了2种植株在形态特征和生理特征的差异,结果表明:在植株形态上,黄化植株相较于正常植株表现矮小,且叶片变小;在主要生理指标上,黄化叶片的叶绿素、花青素、叶黄素以及可溶性糖含量均比正常植株显著降低。通过分析,初步推测闽楠植株黄化是遗传因素起主导作用,后续需进一步观察黄化性状能否稳定表现和探究黄化性状变异的机制,以期为挖掘利用特异种质提供理论参考。

闽楠基因组SSR的开发及其通用性分析

本研究以闽楠优良基因型为供试材料,利用IlluminaMiSeq测序平台对SSR富集文库进行高通量测序,共获得5178284条序列,数据过滤后得到4758764个高质量reads。通过MISA软件搜索到1590126个SSR位点,SSR特征分析表明闽楠SSR的优势重复类型为单核苷酸、二核苷酸和三核苷酸,SSR位点数分别为130952(8.24%)、1229255(77.31%)、200055(12.58%)。通过Prel程序初步对获得的SSR位点进行了多态性评估,并利用Primer3 v2.3.6成功设计了引物。用6个闽楠基因型对136对基因组SSR引物进行筛选验证,最终得到23对条带清晰、特异性好、稳定性好且多态性高的引物。用筛选出的23对多态性引物对8个闽楠近缘种进行通用性检测,结果表明,23对引物在楠属中通用率为100%;在刨花润楠、红楠、黄绒润楠、绒毛润楠中通用率分别为95.65%、86.96%、82.61%、86.96%;在香樟和阴香中通用率分别为78.26%和69.57%。开发的基因组SSR为闽楠遗传多样性研究及分子标记辅助育种提供科学依据。

杉木疏伐强度对林下套种闽楠生长的影响

以江西省永丰县30年生杉木(Cunninghamia lanceolata)林下套种9年生闽楠(Phoebe bournei)幼树为研究对象,设置3种杉木疏伐强度(20%、40%、60%)开展疏伐试验,通过调查林分胸径、树高和冠幅等指标,探讨杉木不同保留密度对林下套种闽楠林分生长的影响。结果表明:随着杉木疏伐强度的增加,闽楠平均胸径、树高、冠幅和单株材积的增长量逐渐增大,不同疏伐强度间差异显著(P<0.05)。杉木60%疏伐强度(保留密度180株/hm^(2))下闽楠的胸径、树高和单株材积增长量均达到最高水平,2018-2020年增长量分别较未疏伐处理(杉木密度450株/hm^(2))下提高了36.42%、6.20%和49.77%,2020-2022年分别提高了50.45%、64.51%和112.20%。表明在闽楠幼树阶段提高林上杉木疏伐强度有利于闽楠的生长,杉木保留密度在180株/hm^(2)以下为宜。本研究为闽楠-杉木异龄复层混交林的经营提供了科学依据。

不同基质配方对闽楠、浙江楠容器苗生长的影响

以泥炭、珍珠岩和稻壳3种基质材料按不同体积比配制成10种基质配方,综合评价闽楠(Phoebe bournei)、浙江楠(Phoebe chekiangensis)3年生容器大苗的生长情况,结果表明:不同基质配方对闽楠、浙江楠的生长有不同影响,10种基质配方中,40%泥炭+40%黄泥+20%稻壳的基质配方适宜闽楠容器大苗培育,80%泥炭+10%黄泥+10%稻壳的基质配方适宜浙江楠容器大苗培育。

不同苗木类型和林地管理方式对闽楠幼林生长的影响

研究不同苗木类型和不同林地管理方式对闽楠(Phoebe bournei)幼林生长的影响。以5种典型闽楠苗木类型和3种林地管理方式进行试验,对闽楠幼林的成活率以及苗高、胸径、冠幅等形态指标进行测量与分析。结果表明2年生容器苗在全光照和林冠下的存活率均最高,达94.67%和90.62%,胸径增长量显著大于其余4种苗木类型。闽楠幼林在机械整地管理下的胸径、树高、冠幅和造林成活率均最高,机械整地配合间作西瓜处理的闽楠幼林生长速率最高。因此,在今后的闽楠造林中推荐选择全光照条件+2年生容器苗+机械整地+间作西瓜管理。

41个闽楠家系苗期生长节律及早期选择

对41个闽楠(Phoebe bournei)家系1年生苗木的生长节律进行观测并综合评价,结果表明7-9月为苗高的旺盛生长期,大部分家系苗高生长速率在8月最大,苗高生长量最大值为41.75±6.56 cm,且各家系间差异较大。地径旺盛生长季则出现在10-11月,大部分家系生长峰值出现在10月,地径生长量最大值为4.12±0.51 mm,各家系间差异较小。对不同闽楠家系苗高和地径综合评价和排序,表现最优的家系为13号,其苗高比参试家系平均苗高(30.46 cm)高37.06%,比平均地径(3.77 mm)高4.48%。按10%的入选率,筛选出13号、12号、15号、10号、14号等5个家系为优良家系。