β-
sitosterol influences
amino acids,
carbohydrates, organic
acids, and other metabolite metabolism and homeostasis largely contributing to better tolerance to
water stress in white clover. β-
sitosterol (BS) could act as an important
plant growth regulator when plants are subjected to harsh environmental conditions. Objective of this study was to examine effects of BS on growth and
water stress tolerance in white clover based on physiological responses and metabolomics. White clover was pretreated with or without BS and then subjected to
water stress for 7 days in controlled growth chambers. Physiological analysis demonstrated that exogenous application of BS (120 μM) could significantly improve stress tolerance associated with better growth performance and photosynthesis, higher leaf relative water content, and less oxidative damage in white clover in response to
water stress. Metabolic profiling identified 78 core metabolites involved in
amino acids, organic
acids,
sugars,
sugar alcohols, and other metabolites in leaves of white clover. For
sugars and
sugar alcohol metabolism, the BS treatment enhanced the accumulation of
fructose,
glucose,
maltose, and myo-
inositol contributing to better
antioxidant capacity, growth maintenance, and osmotic adjustment in white clover under
water stress. The application of BS was inclined to convert
glutamic acid into
proline,
5-oxoproline, and
chlorophyll instead of going to
pyruvate and
alanine; the BS treatment did not significantly affect intermediates of tricarboxylic acid cycle (
citrate,
aconitate, and
malate), but promoted the accumulation of other organic
acids including
lactic acid,
glycolic acid,
glyceric acid,
shikimic acid,
galacturonic acid, and
quinic acid in white clover subjected to
water stress. In addition,
cysteine, an important
antioxidant metabolite, was also significantly improved by BS in white clover under
water stress. These altered
amino acids and organic
acids metabolism could play important roles in growth maintenance and modulation of osmotic and redox balance against
water stress in white clover. Current findings provide a new insight into BS-induced metabolic homeostasis related to growth and
water stress tolerance in plants.