*4.3.1 Phytohormone production*

Endophytes can actively or passively regulate the plant growth by solubilization of phosphate, enhance uptake of phosphorus (P), and/ or plant hormones such as auxin, abscisins, ethylene, gibberellic acid (GA), and indole acetic acid (IAA) [67, 68], among these Gibberellic acid is an important phytohormone. The phytohormone GA, a diterpenoid complex, controls the growth of plants, and promotes flowering, stem elongation, seed germination, and ripening [69, 70]. Fungal endophytes *Sebacina vermifera*, *Piriformospora indica, Colletotrichum* and *Penicillium* are distinguished to have better plant growth promoting effects under unfavorable conditions due to their ability to synthesize enzymes and bioactive metabolites [71–73]. Hamayun et al. [69] reported that fungal endophyte, *Cladosporium sphaerospermum* isolated from soybean plant (*Glycine max*) produced gibberellic acid that induced plant growth in rice and soybean. Metabolite pestalotin analogue, isolated from the endophytic *Pestalotiopsis microspora* exhibited significant gibberellin activity in winter-hazel seeds (*Distylium chinense*) and increased their germination rate [74]. Endophytes, *Fusarium tricinctum* and *Alternaria alternata* produced derivatives of plant hormone indole acetic acid that enhanced the plant growth [75]. A study conducted by Johnson et al. [76] on root colonizing endophyte *P. indica* found that association of fungal endophytes with roots modulated phytohormones involved with growth and development of host plant and enhanced nutrient uptake and translocation especially of phosphorus and nitrogen from the soil.
