Plants cannot move as animals after they are rooted into the ground. Thus, plants have to adapt the environment by modifying their architecture such as leaves, stem, and roots in response to the environmental changes. Phytohohormones are important bioactive chemicals that regulate plant growth. Strigolactones (SLs) are known as a class of phytohormones that inhibit shoot branching as well as communication signals for symbiosis and parasitism. SL levels in root exudates are highly elevated under phosphate (Pi) deficiency. To explore effects of Pi deficiency on shoot branching and SL levels, wild type and SL-related mutants were grown under varying Pi concentrations. In wild type, shoot branching is inhibited, while SL levels are elevated, in response to Pi deficiency. However, the branching inhibition under Pi deficiency is not observed in the SL biosynthesis and signal mutants. Elevated SL levels by Pi deficiency contribute to the inhibition of axillary bud growth. In addition, the mutants show the delayed leaf senescence. Effects of SLs were evaluated on dark-induced and natural leaf senescence. Exogenously applied SLs accelerated leaf senescence under Pi deficiency. The delayed leaf senescence reduces nutrient translocation, resulting in affecting grain yield and seed quality. Thus, evaluation of grain yield and analysis of primary metabolites was performed in the wild-type and SL mutants. In this meeting, I introduce my recent researches on strigolactones (SLs). In the future, I would like to discuss on physiological roles of phytohormones in plant adaptation to global warming as well as to nutrient deficiencies.