根据生物学知识并使用科学语言用英语改写下面内容：However extant research has predominantly concentrated on augmenting the contents of bioactive constituents and overexpression proteins associated with tolerance to drought-rel

Existing studies have mainly focused on increasing the amount of bioactive compounds and overexpressing proteins that are linked to drought tolerance, while neglecting the impact of exogenous application of plant hormones on the drought tolerance of S. miltiorrhiza.