Arbuscular mycorrhiza improved growth performance in Macadamia tetraphylla L. grown under water deficit stress involves soluble sugar and proline accumulation

Water deficit limits plant growth and yield. Arbuscular mycorrhizal (AM) symbiosis is viewed as one of the several methods to improve growth under water deficit. The present study investigated the growth performance in relation to water deficit in two cultivars (H2 and 660) of AM treated macadamia (Macadamia tetraphylla L.) plants. AM treatment significantly improved the growth in macadamia plants that have been subjected to water deficit (7 % soil water content) for 14 days. Leaf water content (LWC) and maximum quantum yield of PSII (F-v/F-m) in AM-associated plants were maintained better than those in the control (well-watered) plants. A positive correlation was observed between LWC and F-v/F-m in H2 cultivar. AM treatment enhanced proline and soluble sugar content in H2 cultivar under water deficit stress. In contrast, only soluble sugars were accumulated in the AM-associated plants of 660 cultivar under water deficit stress. The study concludes that soluble sugars and proline are involved as key signals of osmoregulation defense response, improve water relation in plant tissues, and thereby resulting in improved growth in AM-associated macadamia plants.