Bacillus is one of the main rhizobacteria to have been
used as a study model for understanding many processes.
However, their impact on photosynthetic metabolism has
been poorly studied. The aim of this study was to evaluate
the physiological parameters of pepper (
Capsicum chinense
Jacq.) plants inoculated with
Bacillus spp. strains. Pepper
seeds were inoculated with
Bacillus cereus
(K46 strain)
and
Bacillus spp. (M9 strain; a mixture of
B. subtilis
and
B. amyloliquefaciens
), chlorophyll fluorescence and gas
exchange were evaluated. The ANOVA (P ≤ 0.05) showed
that the maximum photochemical quantum yield of
photosystem II (PSII) (
Fv/
Fm) in plants inoculated with the
M9 strain (0.784) increased with respect to other treatments
(K46: 0.744 and Control: 0.739). Inoculated plants with M9
and K46 strains exhibited an increase of both photochemical
quenching (qP) (by 27% and 24%, respectively) and CO
2
assimilation rate (photosynthesis) (by 20% and 16%,
respectively), when compared with non-inoculated plants.
Furthermore, plants inoculated with M9 and K46 showed
decreased transpiration (61% and 57%, respectively) with
respect to controls. Likewise, both electron transport rate of
PSII (ETR) and PSII operating efficiency (
ΦPSII) increased
in inoculated plants. However, only plants inoculated
with the M9 strain showed enhancements on all growth
characteristics. Our results therefore show that inoculating
plants with M9 strain positively influenced the performance
of the photosynthetic mechanism in pepper plants to increase
chlorophyll fluorescence and gas exchange parameters.
Promotion of photosynthetic capacity in pepper was due
to increased ETR in the thylakoid membranes, which was
promoted by the bacteria. M9 strain could even be used in
sustainable agriculture programs.
