龙须枣曲枝的解剖学观察

doi:10.16420/j.issn.0513-353x.2020-0561

摘要/Abstract

摘要：

以龙须枣（Ziziphus jujuba Mill var. tortuosa）一年生枝条的扭曲枝段和直立枝段为试验材料,采用木材切片法和木材离析技术,观察比较枝条形态、解剖结构特点及导管分子特征。扭曲枝段和直立枝段解剖结构的差异主要表现在异常次生结构的数量、形态和分布上。与直立枝段相比较,扭曲枝段附加维管束数量较多,出现3个附加维管束相毗邻,相对集中于枝条内弯处;木间韧皮部的数量与直立枝段相差不多,其末端膨大,与直立枝段的略带弯曲的椭圆柱状不同,相对集中分布于枝条外弯处;髓维管束数量略微减少。从细胞水平看,扭曲枝段内弯处和外弯处导管分子均属于网纹导管、单穿孔,具有多种形态。其中,内弯处两端有尾和两端倾斜的导管分子数分别比其外弯处少28.0%和20.2%,两端无尾、一端倾斜和两端水平的导管分子数分别多17.9%、375.0%和200.0%,一端有尾导管分子数相同,导管分子端壁倾角比外弯处大10.1%,导管分子长度比外弯处的短16.4%,直径比外弯处的小18.6%。提出 “异常结构—空间差异—相互协调”的假说。龙须枣的曲枝性可能是由附加维管束、木间韧皮部和髓维管束等3种异常次生结构的数量、机械拉力、同化产物的输导和利用在空间上的差异和相互协调所造成的枝条不同位置的生长速率和受力不均衡的结果。

关键词: 枣, 曲枝, 异常次生结构, 导管分子

Abstract:

Taking the twisted tortuous branch segment and twisted straight branch segment of annual branches in Ziziphus jujuba Mill. var. tortuosa as experimental materials,the morphological,anatomical and vessel characteristics of its branches were observed and compared by xylotomy and wood segregation techniques. The differences of anatomical structures between twisted tortuous branch segment and twisted straight branch segment were mainly manifested in the number,shape and distribution of abnormal secondary structures. Compared with the twisted straight branch segment,the number of auxillary bundles in twisted tortuous branch segments was more,and there were three auxillary bundles adjacent to each other,which were relatively concentrated in the inner bend of the segments;The number of interxylary phloem was about the same as that of the twisted straight branch segment,and its end expanded,which was different from the slightly curved elliptic columnar shape of the twisted straight branch segment,and relatively concentrated in the outer bend of the segments;The number of medullary vascular bundles was slightly reduced. At the cellular level,the vessel elements at the inner and outer bends of the twisted tortuous branch segments of the variety were all reticulate vessels with single perforation and various shapes. Among them,the number of vessel elements with tails at both ends and sloped at both ends at the inner bend were 28.0% and 20.2% less than those at the outer bend,respectively. The number of vessels without tails at either ends,sloped at one end and horizontal at both ends were 17.9%,375.0% and 200.0% more,respectively. The number of vessels with one tail at one end was the same. The end wall slope of end wall was 10.1% larger than that at the outer bend,and the length of vessel element was 16.4% shorter than that at the outer bend,while the diameter was 18.6% smaller than that at the outer bend. The hypothesis of “abnormal structure-spatial difference-coordination”was put forward. The tortuous branch traits of Z. jujuba var. tortuosa may be the result of the unbalanced growth rates and forces at different locations of the branches caused by the spatial difference and coordination of the number,the mechanical tension,the transport and utilization of the assimilated products of the three abnormal secondary structures,namely the auxillary bundle,interxylary phloem and medullary bundle.

Key words: Ziziphus jujuba, tortuous branch, abnormal secondary structure, vessel element

中图分类号:

S665.1

郭学民, 王芯蕊, 王影影, 李政, 苗宁宁, 王昭君. 龙须枣曲枝的解剖学观察[J]. 园艺学报, 2021, 48(9): 1653-1664.

GUO Xuemin, WANG Xinrui, WANG Yingying, LI Zheng, MIAO Ningning, WANG Zhaojun. Anatomical Observation on the Tortuousness of Ziziphus jujuba var. tortuosa Branches[J]. Acta Horticulturae Sinica, 2021, 48(9): 1653-1664.

图/表 6

图1 龙须枣枝条形态 TB：扭曲枝段;TS：直立枝段;IS：扭曲枝段内弯处;OS：扭曲枝段外弯处。

Fig. 1 The branch shape of Ziziphus jujuba var. tortuosa TB：Twisted tortuous branch segment;TS：Twisted straight branch segment;IS;The inner bend of twisted tortuous branch segment;OS：The outer bend of twisted tortuous branch segment.

图2 龙须枣直立枝段与扭曲枝段枝皮的解剖结构比较 1：直立枝段;2：扭曲枝段。a1：完整的枝条横切,示5个分散的附加维管束（AB）、2个木间韧皮部（IP）和4个髓维管束（MB）;a2：枝条横切,内弯处切口用箭头示出,以及枝条的10个附加维管束中有9个（包括2个毗邻附加维管束和4个单独附加维管束,其中1个毗邻附加维管束含3个附加维管束,另1个含2个附加维管束）相对集中在内弯处,而5个木间韧皮部中有4个相对集中在枝条外弯处;b：枝皮,示表皮（Ep）、周皮（Pe）、皮层（Co）、次生韧皮部纤维带（SB）和次生韧皮部（SP）;c：枝皮外侧纵切,示封闭型皮孔（Le）的结构、2条平行的次生韧皮纤维带（SB）和2个分泌腔（SC）;d1：1个偏心的起源于次生木质部（SX）的附加维管束横切图,示其木质部的非对称性结构和外侧的次生韧皮纤维带;d2：正心的、起源于外周薄壁细胞的附加维管束横切;e1：2个毗邻的正心的起源于外周薄壁细胞的附加维管束（AB）与1个正在发育的正心的起源于外周薄壁细胞的附加维管束（圆圈）横切图,示次生韧皮纤维带位于附加维管束内侧;e2：1个偏心的、来源于次生木质部分裂的附加维管束,示其与次生木质部相连接（箭头）及其外侧弧状次生韧皮纤维带;f1：源于外周薄壁细胞的附加维管束（AB）纵切图,示周韧维管束独立于次生木质部,沿枝条轴向伸长;g1：附加维管束的纵切,箭头指向垂直于枝条长轴方向排列的木质部细胞;h1：附加维管束末端的纵切放大图,示由排列不规则的次生木质部细胞构成的球形末端;i1：2个毗邻相连的附加维管束横切;j1：1个偏心的、起源于次生木质部的附加维管束横切放大图,与次生木质部相连接;f2：3个毗邻附加维管束横切,示1个起源于外周薄壁细胞的附加维管束（左）和2个由次生木质部分裂形成的附加维管束相互连接,以及次生韧皮纤维带的局部分布;g2：1个起源于外周薄壁细胞的附加维管束纵切,示其梭形形态以及位于附加维管束内侧的次生韧皮纤维带;h2：1个由次生木质部裂分形成的附加维管束纵切,示其椭圆形形态、位于附加维管束外侧的次生韧皮纤维带以及2个分泌腔;k1：枝条纵切,示2个起源于外周薄壁细胞（独立于次生木质部）的附加维管束（AB）,次生韧皮纤维带（SB）在其内侧,和起源于次生木质部（与次生木质部相连）的附加维管束（AB）（左）,次生韧皮纤维带（SB）在其外侧（双箭头）;i2、j2：1个与次生木质部连接的附加维管束纵切,示2条位于附加维管束外侧的次生韧皮纤维带。PX. 初生木质部;Sc. 石细胞;Pi. 髓。

Fig. 2 Comparison of anatomical structures of bark between twisted straight and twisted tortuous branch segments of Ziziphus jujuba var. tortuosa branches 1. Twisted straight branch segment;2. Twisted tortuous branch segment. a1. Complete branch transection,showing distribution of five scattered auxillary bundles（AB）,two interxylary phloems（IP）and four medullary bundles（MB）;a2. Transection of the branch,showing the incision（arrow）marking the inner bend of twisted tortuous branch segment,and that nine of the ten auxillary bundles which consisted of two adjacent auxillary bundles and four separate auxillary bundles,in which one adjacent auxillary bundle contained three auxillary bundles,and the other contained two auxillary bundles,were relatively concentrated on the inner bend of the branch,while four of the five interxylary phloems were relatively concentrated on the outer bend of the branch;b. The bark,showing epidermis（Ep）,periderm（Pe）,cortex（Co）,secondary phloem fiber band（SB）and secondary phloem（SP）;c. Longitudinal section of the bark,showing the structure of the closed lenticel （Le）,two parallel secondary phloem fiber bands（SB）and two secretory cavities（SC）;d1. Detailed view of one off-center auxillary bundle transection formed by the fission of secondary xylem（SX）,showing the asymmetric structure of its xylem and lateral secondary phloem fiber band;d2. Transection of an in-center auxillary bundle originated from peripheral parenchyma cells;e1. Two in-center auxillarybundles（AB）originated from peripheral parenchyma cells and one developing and in-center auxillary bundle（circle）originated from peripheral parenchyma cells,showing the secondary phloem fiber band on the inside of auxillary bundles;e2. Transection of a off-center auxillary bundle formed by the fission of secondary xylem,showing the pattern of its connection with secondary xylem（arrow）and its outer arc-shaped secondary phloem fiber band;f1. Longitudinal section of one auxillary bundle（AB）originated from peripheral parenchyma cells,the arrow showing some secondary xylem cells arranged perpendicular to the long axis of the branch. h1. Longitudinal section through the end of one auxillary bundle,showing a spherical end of an auxillary bundle consisting of irregularly arranged secondary xylem cells;i1. Transection of two adjacent auxillary bundles;j1. Detailed view of transection of one off-center auxillary bundle formed by the fission of secondary xylem,showing its connection with secondary xylem;f2. Transection of three adjacent auxillary bundles connected together,showing one auxillary bundle（Left）originated from peripheralparenchyma cells and two auxillary bundles formed by the fission of secondary xylem,the pattern of their interconnection and the distribution of secondary phloem fiber band;g2. Longitudinal section of one auxillary bundle originated from peripheral parenchyma cells,showing its fusiform shape and secondary phloem band located in the inner side of the auxillary bundle;h2. Longitudinal section of one auxillary bundle fiberformed by the fission of secondary xylem,showing its oval shape,secondary phloem fiber band located outside the auxillary bundle and two secretory cavities;k1. Tangential section of one branch, showing two auxillary bundles（AB）originated from peripheral parenchyma cells（Independent of the secondary xylem）,in which the secondary phloem fiber band（SB）was on its inner side,and one auxillary bundle（AB）（Left）formed by the fission of secondary xylem（Associated with the secondary xylem）,in which the secondary phloem fiber band（SB）was outside it（double arrows）;i2,j2. Section of one auxillary bundle connecting with secondary xylem,Longitudinal showing two secondary phloem fiber bands located outside the auxillary bundle. PX. Primary xylem;Sc. Sclereid;Pi. Pith.

图3 龙须枣直立枝段与扭曲枝段次生木质部和髓的解剖结构比较 1：直立枝段;2：扭曲枝段。a1：次生木质部横切,示导管（V）和单列射线（UR）;b1：次生木质部纵切,示网纹导管和单列射线的高度;c1：枝条横切,示木间韧皮部（IP）与次生木质部（SX）外的次生韧皮纤维带分布;d1：木间韧皮部外侧横切放大图,示韧皮部的组成;e1：木间韧皮部髓端放大图,示单向形成层（UC）;f1：次生木质部切向切面,示木间韧皮部横切面的椭圆形形态;g1：髓横切;h1. 髓纵切;i2：图2中a2的局部放大,示4个木间韧皮部的分布及其末端膨大的形态和1个髓维管束（MB）形态;j1. 1个近对称的髓维管束横切放大图,示其近对称性形态;k1. 1个椭圆形髓维管束横切放大图,示其非对称性形态;l1：髓维管束中央纵切,中央韧皮组织和外侧次生木质部。AB：附加维管束;SB：次生韧皮纤维带;PX：初生木质部;Pi：髓。

Fig. 3 Comparison of anatomical structures of secondary xylem and pith between twisted straight and twisted tortuous branch segments of Z. jujuba var. tortuosa branches 1. Twisted straight branch segment;2. Twisted tortuous branch segment. a1. Transection of secondary xylem,showing vessels（V）and uniserate rays （UR）;b1. Tangential section of secondary xylem,showing reticulate vessel and the height of uniserate ray;c1. Transection of the branch, showing the distribution of interxylary phloems（IP）and secondary phloem fiber band outside secondary xylem;d1. Detailed view of transaction of the outer part of an interxylary phloem,showing composition of the phloem;e1. Detailed view of pith end of interxylary phloem,showing unidirectional cambium;f1. Tangential section of secondary xylem,showing the oval shape of the interxylary phloem transection;g1. Transection of the pith;h1. Longitudinal section of pith;i2. Detailed view of figure a2 in fig.2,showing the distributions of four interxylary phloems and their shapes of enlarged ends,and the shape of one medullary bundle（MB）;j1. Detailed view of one medullary bundle transection,showing its nearly symmetrical shape;k1. Detailed view of one elliptical medullary bundle transection,showing its asymmetric shape;l1. Detailed view of longitudinal section through one medullary bundle,showing central phloem tissue and peripheral secondary xylem. AB：Auxillary bundles;SB：Secondary phloem fiber band;PX：Primary xylem;Pi：Pith.

图4 龙须枣扭曲枝段导管分子形态 A. 两端近水平,两端具尾;B. 两端倾斜,一端具尾;C. 两端倾斜,两端无尾;D. 一端近水平,一端具尾;E. 两端近水平,两端无尾;E. 两端倾斜,两端具尾。

Fig. 4 Vessel element shapes in twisted tortuous branch segment of Ziziphus jujuba var. tortuosa branches A. Both end walls are horizontal,and tails in both end walls;B. Both end walls are slope,and tail in one end wall;C. Both end walls are slope,and no tail in either end wall;D. One end wall is horizontal,and tail in one end wall;E. Both end walls are near horizontal,and no tail in either end walls;F. Both end walls are slope,and tails in both end walls.

表1 龙须枣扭曲枝段中导管分子大小与尾类型

Table 1 Size and frequency of tail types of vessel elements in twisted tortuous branch segment of Z. jujuba var. tortuosa

部位 Position	大小/µm Size		尾类型 Tail type
部位 Position	长度 Length	直径 Diameter	两端有尾 Both tail	一端有尾 One tail	两端无尾 No tail
内弯侧 Inner bend	259.3 ± 79.1	39.8 ± 11.5	18	36	46
外弯侧 Outer bend	310.3 ± 31.2^**	48.9 ± 11.4^*	25	36	39

表2 龙须枣扭曲枝段中导管分子端壁类型与端壁倾角

Table 2 Frequency of types of end wall slope of vessel elements in twisted tortuous branch segment of Z. jujuba var. tortuosa

材料 Material	端壁类型比例/% End wall type			端壁倾角/° End wall slope
材料 Material	两端倾斜 Both end walls are slope	一端倾斜 One end wall is slope	两端水平 Both end walls are horizontal	端壁倾角/° End wall slope
内弯处The inner bend	75	19	6	53.2 ± 13.9^**
外弯处The outer bend	94	4	2	48.3 ± 11.9

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