角倍蚜虫瘿的组织学结构与功能解析

The anatomical structure and function of horned gall induced by Schlechtendalia chinensis

五倍子是一类具有重要的经济价值的蚜虫虫瘿,在中医、化工、纺织、食品等行业用途广泛。角倍是我国五倍子生产中最重要的一种,是由角倍蚜Schlechtendalia chinensis在盐肤木Rhus chinensis叶轴翅上刺激形成,产量占我国五倍子总产量的75%以上。本研究发现五倍子虫瘿柄部分化出了异常膨大的木质部与叶轴直接相连以稳定支撑虫瘿。虫瘿壁由疏松的薄壁组织构成,有效降低了虫瘿重量并维持虫瘿的足够硬度。柄部除了异常膨大的木质部外,还分布有大量的维管束及裂生道,并从虫瘿柄部一直延伸至虫瘿末端。维管束及裂生道有大量弯曲的细小分枝,形成包裹整个虫瘿的网状结构。从内壁到外壁维管束与裂生道逐渐减小,这既能防止外源微生物入侵,也有效阻止虫瘿内水分向外挥发,保持了虫瘿内蚜虫所需的高湿度生境。内壁大量的分枝有利于虫瘿内蚜虫吸收营养,网状分枝结构在有限倍体中增大了裂生道及维管束数量、体积与表面积,使其能运输更多的营养及提供最大面积的物质交换场所。封闭的虫瘿外壁长有大量绒毛,绒毛中分布有气孔,绒毛有保护功能,可以抵御其它食草动物的攻击;虫瘿内壁粗糙,凹凸不平,有利于蚜虫的附着,同时增加了内壁的表面积;内壁中还分布有大量的缝隙和孔,这些缝隙可以吸收蚜虫排泄的蜜露,使瘿内能保持清洁。本文通过解析角倍蚜虫瘿的结构和功能,从生态学角度阐明蚜虫与植物之间相互适应关系,为研究昆虫与植物协同进化提供新的有力证据。

With the important economic value,Chinese gallnut is widely used in traditional Chinese medicine,chemical industry,textile,food and so on.The horned gall was induced by Schlechtendalia chinensis in winged rachis of Rhus chinensis.It is the most important gallnut and accounted for more than 75% of total gallnut production around China.In order to supporting the gall stablely,petiole of the gall hypertrophyed intumescent xylem which connect with rachis.Lignin of gall obvious is higher than in the leaf and the wall is filled with loose parenchyma,which made gall become lighter and maintainedappropriate stiffiness at the same time.Petiole of the gall distributeabundant vascular bundles and laticifers except intumescent xylem.Vascular bundle and laticifers gradual gather and become thicker from the top of gall to petiole and focus on intine,and then which connected with phloem and newly formed sieve tube in rachis.There are abundant thin and crooked branches in the end of laticifers.It forms efficient net circulatory system which is complicated and stable.The branches are tapering from ektexine to intine,preventing the invade of bacteria and other microbes.At the same time,it can efficiently avoid the moisture evaporating can maintain high humidity inside the gall for aphids.The flexuous complicated net increase the number of vascular bundle,laticifers,volume and superficial area in the limited wall.It can transport more nutrition and provide the largest areas for exchanging substance.There are plenty of tomentum and stoma interspersed in the surface of the gall.Tomentum can protect the gall from herbivore and protect aphids from natural enemy.Intine is rough and uneven,that benefit aphids adhere and increase superficial area of intine.There are abundant small openings in intine,which are considered to absorb honeydew so maintain clean internal environment.This study illuminates how the aphid and plant adapt to each other with the analysis on the structure of horned gall,and provids new evidence for studying the co-evolution of plant and insect.