Abstract
Root exudates serve as crucial mediators for the information exchange
between plants and soil, which is an important evolutionary mechanism
for plants to adapt to environmental changes. In this study, 15
different abiotic stress models were established using various stress
factors, including drought (D), high-temperature (T), nitrogen
deficiency (N), and phosphorus deficiency (P) and their combinations. We
investigated their effects on the seedling growth of Salvia
miltiorrhiza Bunge and the activities of urease (S-UE), nitrite
reductase (S-NiR), nitrate reductase (S-NR), phosphotransferase (S-PT),
and catalase (S-CAT), as well as the contents of polysaccharides in the
culture medium. The results showed that the growth of S.
miltiorrhiza was inhibited under 15 stress conditions, among which 13
stress conditions could increase the root-shoot ratio. These 15 stress
conditions significantly down-regulated the activity of S-NR,
synergistic stresses of drought and nitrogen deficiency (DN) and
synergistic stresses of high-temperature and nitrogen deficiency (TN)
significantly up-regulated the activity of S-NIR
(p <0.05). The N, D, T, synergistic stresses of drought
and high-temperature (DT), DN, synergistic stresses of drought and
phosphorus deficiency (DP), and synergistic stresses of
high-temperature, nitrogen deficiency, and phosphorus deficiency (TNP)
stresses conditions significantly increased the activity of S-UE
(p <0.05). The activity of soil enzyme S-PT could be
down-regulated under most stress conditions, but only D and T stresses
could significantly up-regulate S-PT activity (p <0.05).
The N, DN, and TN stresses conditions significantly reduced S-CAT
activity. The content of total polysaccharides in soil was decreased
under most stress conditions, and P, DT, and synergistic stresses of
drought, high-temperature, and phosphorus deficiency (DTP) stresses were
significantly decreased (p <0.05). These results
indicated that abiotic stress inhibited the growth of S.
miltiorrhiza and altered the root secretion behavior. Plants respond to
different abiotic stresses by regulating root secretions, including
enzymes of the soil nitrogen cycle, phosphorus transport-related
enzymes, and antioxidant enzymes. In conclusion, plants regulate the
utilization of rhizosphere substances by regulating the intensity of
soil enzymes and polysaccharides secreted by roots to cope with abiotic
stress. At the same time, soil carbon sequestration is affected by the
adverse environment, which restricts the input of organic matter into
the soil.