Effects of exogenous IAA in regulating photosynthetic capacity, carbohydrate metabolism and yield of Zizania latifolia

The effects of plant hormones on plant growth of Zizania latifolia are still considered to be the difficult and hot spots. The present study was carried out to investigate the regulation mechanism of exogenous indole-3-acetic acid (IAA) and IAA transport inhibitor (2,3,5-triiodobenzoic acid, TIBA) on yield, photosynthesis capacity, carbon assimilation and interaction of plant-fugal of Ustilago esculenta Henn. These results displayed that exogenous IAA led to significant increases in gall growth rate, swollen gall volume and biomass accumulation, promoting yield per unit of swollen gall in Z. latifolia. Exogenous IAA could improve the net photosynthetic rate (Pn), which contributed to higher stomatal conductance (Gs) and transpiration rate (Tr) in plant. TIBA treatment markedly inhibited the plant growth and photosynthetic rate. Contents of sucrose, glucose, fructose and total soluble sugar by IAA were significantly higher than control, whereas these parameters were declined by TIBA. Exogenous TIBA resulted in accumulation of starch (unfavorable to sugar metabolism) and crude fiber contents (declined swollen gall quality). Additionally, it was firstly reported the stimulation of exogenously applied of IAA and TIBA on plant growth and hyphae growth of U. esculenta. Microscopic analyses revealed that abundant hyphae were well-distributed closely to cell wall after IAA treatment, which could produce endogenous plant hormones, promoting the swollen cell structure enlargement. And hyphal aggregation over-growth by TIBA treatment indicated the vigorously increase of hyphae was surpassed the plant self-growth. These changes were greatly contributed to the increase of endogenous IAA content. The utilization of exogenous IAA and TIBA in present study proved IAA played a dominant role in regulating Z. latifolia growth.