Abstract
The culturable endophytic fungus
Serendipita indica
has many beneficial effects on plants, but whether and how it affects physiological activities and phosphorus (P) acquisition of tea seedlings at low P levels is unclear. The objective of this study was to analyze the effects of inoculation with
S
.
indica
on growth, gas exchange, chlorophyll fluorescence, auxins, cytokinins, P levels, and expressions of two phosphate transporter (
PT
) genes in leaves of tea (
Camellia sinensis
L. cv. Fudingdabaicha) seedlings grown at 0.5 μM (P
0.5
) and 50 μM (P
50
) P levels. Sixteen weeks after the inoculation,
S
.
indica
colonized roots of tea seedlings, with root fungal colonization rates reaching 62.18% and 81.34% at P
0.5
and P
50
levels, respectively. Although plant growth behavior, leaf gas exchange, chlorophyll values, nitrogen balance index, and chlorophyll fluorescence parameters of tea seedlings were suppressed at P
0.5
versus P
50
levels, inoculation of
S
.
indica
mitigated the negative effects to some extent, along with more prominent promotion at P
0.5
levels.
S
.
indica
inoculation significantly increased leaf P and indoleacetic acid concentrations at P
0.5
and P
50
levels and leaf isopentenyladenine, dihydrozeatin, and transzeatin concentrations at P
0.5
levels, coupled with the reduction of indolebutyric acid at P
50
levels. Inoculation of
S
.
indica
up-regulated the relative expression of leaf
CsPT1
at P
0.5
and P
50
levels and
CsPT4
at P
0.5
levels. It is concluded that
S
.
indica
promoted P acquisition and growth in tea seedlings under P deficit conditions by increasing cytokinins and indoleacetic acid and
CsPT1
and
CsPT4
expression.