Braunberger Peter G, Abbott L K, Robson A D
Soil Science and Plant Nutrition, Faculty of Agriculture, The University of Western Australia, Nedlands, Western Australia 6009, Australia.
New Phytol. 1996 Dec;134(4):673-684. doi: 10.1111/j.1469-8137.1996.tb04933.x.
In a mediterranean environment, a hot and dry summer is followed by a cool and rainy winter, the growing season. Arbuscular mycorrhizal (AM) fungi survive in dry soil in the summer and are able to colonize newly emerged plants in winter. However, late summer and autumn rains are frequently followed by periods of drought, resulting in the wetting and drying of the soil before the onset of regular winter rains. The results of three experiments investigating the effect of wetting and drying of soil on the subsequent infectivity of different AM fungi and their individual propagules are presented. In a first experiment, pot-culture inoculum of Acaulospora laevis Gerd. & Trappe, Glomus invermaium Hall, or fine endophytes, each containing a mixture of propagule forms, was mixed into pots of steam-sterilized soil with low phosphorus content. Pots were treated with a wetting and drying cycle where the soil was watered to field capacity for three consecutive days and then left to dry to a water content of less than 1.5% g g . Infectivity was assessed in a subsequent growth cycle planted with clover. In a second experiment, the infectivity of spores of A. laevis, Glomus monosporum Gerd. & Trappe or Scutellospora calospora (Nicol & Gerd.) Walkers & Sanders, and of dried mycorrhizal root fragments of G. invermaium or S. calospora was assessed after a wetting and drying cycle in which the soil was watered to field capacity for seven consecutive days before drying. In a third experiment, the infectivity of the extraradical hyphae of G. invermaium after wetting and drying was assessed. AM fungi and their individual propagules responded differently to wetting and drying. The infectivity of pot-culture inoculum of A. laevis, G. invermaium and fine endophytes was increased, decreased and unaffected, respectively, by wetting and drying. The infectivity of spores of A. laevis and G. monosporum was increased by wetting and drying but the infectivity of spores of 5. calospora was not affected. Infectivity of mycorrhizal root fragments of G. invermaium and S. calospora was decreased and increased, respectively, by wetting and drying. Finally, the infectivity of the extraradical hyphae of G. invermaium was eliminated by a wetting and drying cycle. These results indicate that the development and function of mycorrhizas after late summer and early autumn rains may be limited by the occurrence and predominance of propagules of different AM fungi.
在地中海环境中，炎热干燥的夏季之后是凉爽多雨的冬季，即生长季节。丛枝菌根（AM）真菌在夏季的干燥土壤中存活，并能够在冬季定殖于新出土的植物上。然而，夏末和秋季降雨之后常常紧接着干旱期，导致在冬季正常降雨开始之前土壤经历干湿交替。本文展示了三项实验的结果，这些实验研究了土壤干湿交替对不同AM真菌及其单个繁殖体后续感染能力的影响。在第一个实验中，将含有繁殖体形式混合物的平滑无梗囊霉（Acaulospora laevis Gerd. & Trappe）、倒卵球囊霉（Glomus invermaium Hall）或细内生菌的盆栽接种物，混入低磷含量的蒸汽灭菌土壤盆中。对花盆进行干湿循环处理，即连续三天将土壤浇水至田间持水量，然后让其干燥至含水量低于1.5%（克/克）。在随后种植三叶草的生长周期中评估感染能力。在第二个实验中，在干湿循环后评估平滑无梗囊霉、单孢球囊霉（Glomus monosporum Gerd. & Trappe）或美孢盾巨孢囊霉（Scutellospora calospora (Nicol & Gerd.) Walkers & Sanders）的孢子，以及倒卵球囊霉或美孢盾巨孢囊霉的干燥菌根根段的感染能力，该干湿循环为在干燥前连续七天将土壤浇水至田间持水量。在第三个实验中，评估倒卵球囊霉根外菌丝在干湿处理后的感染能力。AM真菌及其单个繁殖体对干湿交替的反应不同。平滑无梗囊霉、倒卵球囊霉和细内生菌的盆栽接种物的感染能力，分别因干湿交替而增加、降低和不受影响。平滑无梗囊霉和单孢球囊霉孢子的感染能力因干湿交替而增加，但美孢盾巨孢囊霉孢子的感染能力未受影响。倒卵球囊霉和美孢盾巨孢囊霉菌根根段的感染能力，分别因干湿交替而降低和增加。最后，倒卵球囊霉根外菌丝的感染能力因干湿循环而消除。这些结果表明，夏末和秋初降雨后菌根的发育和功能，可能受到不同AM真菌繁殖体的出现和优势的限制。
