Huang Yu-Ling, Zimmerman Naupaka B, Arnold A Elizabeth
School of Plant Sciences, The University of Arizona, 1140 E. South Campus Drive, Tucson, AZ 85721, USA.
National Museum of Natural Science, 1 Guancian Rd., Taichung 40453, Taiwan.
J Fungi (Basel). 2018 May 16;4(2):58. doi: 10.3390/jof4020058.
Fungal endophytes are diverse and widespread symbionts that occur in the living tissues of all lineages of plants without causing evidence of disease. Culture-based and culture-free studies indicate that they often are abundant in the leaves of woody angiosperms, but only a few studies have visualized endophytic fungi in leaf tissues, and the process through which most endophytes colonize leaves has not been studied thoroughly. We inoculated leaf discs and the living leaves of a model woody angiosperm, , which has endophytes that represent three distantly-related genera (, , and ). We used scanning electron microscopy and light microscopy to evaluate the timeline and processes by which they colonize leaf tissue. Under laboratory conditions with high humidity, conidia germinated on leaf discs to yield hyphae that grew epiphytically and incidentally entered stomata, but did not grow in a directed fashion toward stomatal openings. No cuticular penetration was observed. The endophytes readily colonized the interiors of leaf discs that were detached from living leaves, and could be visualized within discs with light microscopy. Although they were difficult to visualize within the interior of living leaves following in vivo inoculations, standard methods for isolating foliar endophytes confirmed their presence.
真菌内生菌是多样且广泛分布的共生体，存在于所有植物谱系的活组织中，且不会引发疾病迹象。基于培养和不依赖培养的研究表明，它们在木质被子植物的叶片中通常数量丰富，但仅有少数研究观察到叶片组织中的内生真菌，并且大多数内生菌定殖于叶片的过程尚未得到充分研究。我们对接种了叶盘以及一种模式木质被子植物的活体叶片，该植物的内生菌代表了三个亲缘关系较远的属（、和）。我们使用扫描电子显微镜和光学显微镜来评估它们定殖于叶片组织的时间线和过程。在高湿度的实验室条件下，分生孢子在叶盘上萌发产生菌丝，这些菌丝在叶面上附生生长并偶然进入气孔，但并非以定向方式朝着气孔开口生长。未观察到角质层穿透现象。内生菌很容易定殖于从活体叶片上分离下来的叶盘内部，并且可以通过光学显微镜在叶盘内观察到。尽管在活体叶片体内接种后，它们在叶片内部难以观察到，但分离叶内生菌的标准方法证实了它们的存在。
