Viscin tissue of the dwarf misteltoe Arceuthobium americanum (Viscaceae): how does it develop, what is it made of, and how does it function in explosive seed discharge

寄生寄生是寄生在其他植物上的一群开花植物，寄生在其他植物上，吸收寄主的水分和矿物质。寄生寄生在北美的针叶树上，寄生于针叶树，除了偷走水分和矿物质外，还带走糖分。因此，这些寄生虫会在寄主身上引起疾病，是严重的森林害虫：据估计，在加拿大西部，寄生寄生每年造成400万立方米的木材生长损失，造成数十亿美元的损失。此外，矮小的寄生寄生会导致枝条过多的枯死森林，而不是作为火灾的燃料并使树木容易受到包括山松甲虫在内的其他害虫的攻击。在所有槲寄生的单籽果实中发现的粘质组织是一种独特的胶状组织，称为粘素，它仍然作为一层涂层留在分散的种子上，以促进其附着到它触及的任何表面，包括下一个寄主。在寄生虫的传播过程中，矮生槲寄生中的粘质组织起着额外而关键的作用：其他槲寄生的种子是由鸟类传播的，而矮生槲寄生的种子几乎完全是通过从成熟果实强制排放到最长20米的距离来传播的。在果实发育过程中，这种粘质组织以某种方式吸收水分。产生爆炸放电所需的静水力。不列颠哥伦比亚省坎卢普斯汤普森河大学正在开展的一个项目正在研究粘素组织的发育、结构和化学，以及探索称为水通道蛋白的水通道如何将水引导到粘素组织以建立流体静力。在更好地了解粘素组织和手头的爆炸性排放之后，致力于减少矮生槲寄生感染引起的疾病的工作可以取得进展。

Mistletoes, which spread solely by seed, are a group of flowering plants that are parasitic on other plants, absorbing water and minerals from their host.  Dwarf mistletoes, genus Arceuthobium, are parasites of conifers in North America, and, in addition to pilfering water and minerals, also take sugars.  Consequently, these parasites cause disease in their hosts, and are serious forest pests: it is estimated that dwarf mistletoes cause an annual growth loss of 4 million m3 of wood in western Canada, at a cost of several billion dollars.  Furthermore, dwarf mistletoe infestation leads to dead standing forests with excessive branches, notorious as fuel for fire, and predisposes the trees to attack by other pest organisms including mountain pine beetle.        Found within the single-seeded fruit of all mistletoes is a unique gelatinous tissue called viscin, which remains as a coating on the dispersed seed to facilitate its adherence to any surface it strikes, including the next host.  The viscin tissue in dwarf mistletoes plays an additional and critical role in parasite dispersal: whereas the seeds of other mistletoes are spread by birds, those of dwarf mistletoes are dispersed almost exclusively by forcible discharge from mature fruit to a maximum distance of 20 m.  The gelatinous viscin tissue somehow imbibes water during fruit development, which generates a hydrostatic force needed for explosive discharge.      Viscin tissue is crucial for the transmission and proliferation of dwarf mistletoes as insidious forest pathogens.  A project being carried out at Thompson Rivers University in Kamloops, British Columbia is examining the development, structure, and chemistry of the viscin tissue as well as exploring how water channels called aquaporins might direct water toward the viscin tissue in order to build the hydrostatic force.  With a better understanding of the viscin tissue and explosive discharge in hand, work toward reducing disease caused by dwarf mistletoe infection can advance.