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

槲寄生是一种开花植物，寄生在其他植物上，从宿主身上吸收水分和矿物质。 矮槲寄生是北美针叶树的寄生虫，除了偷水和矿物质外，还吃糖。 因此，这些寄生虫在其宿主中引起疾病，并且是严重的森林害虫：据估计，矮槲寄生在加拿大西部每年造成400万立方米木材的生长损失，花费数十亿美元。 此外，矮槲寄生的侵扰导致树木枯死，树枝过多，是臭名昭著的火灾燃料，并使树木容易受到其他有害生物的攻击，包括山松甲虫。 在所有槲寄生的单种子果实中发现了一种独特的凝胶状组织，称为viscin，它作为分散种子的涂层，以促进其粘附在任何表面，包括下一个宿主。 在寄生虫传播中，矮槲寄生的内脏组织起着额外的关键作用：而其他槲寄生的种子是由鸟类传播的，矮槲寄生的种子几乎完全是通过从成熟果实中强行排出而传播的，最大距离为20米。 在果实发育过程中，凝胶状的粘蛋白组织以某种方式吸收水分，从而产生爆炸性放电所需的静水压力。 槲寄生是森林中的一种重要病原菌，其寄生组织对槲寄生的传播和繁殖至关重要。 位于不列颠哥伦比亚省坎卢普斯的汤普森河流大学正在进行一个项目，该项目正在研究内脏组织的发育、结构和化学，并探索称为水通道蛋白的水通道如何将水引导到内脏组织，以建立静水压力。 随着对内脏组织和爆炸性放电的更好理解，减少矮槲寄生感染引起的疾病的工作可以向前推进。

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.