Summer Warming Limited Bud Output Drives a Decline in Daughter Shoot Biomass through Reduced Photosynthetis of Parent Shoots in Leymus chinensis Seedlings

Understanding how summer warming influences the parent and daughter shoot production in a perennial clonal grass is vital for comprehending the response of grassland productivity to global warming. Here, we conducted a simulated experiment using potted Leymus chinensis, to study the relationship between the photosynthetic activity of parent shoots and the production of daughter shoots under a whole (90 days) summer warming scenario (+3°C). The results showed that the biomass of parents and buds decreased by 25.52% and 33.45%, respectively, under warming conditions. The reduction in parent shoot biomass due to warming directly resulted from decreased leaf area (18.03%), chlorophyll a (18.27%), chlorophyll b (29.21%) content, as well as a reduction in net photosynthetic rate (7.32%) and the maximum quantum efficiency of photosystem II (PSII) photochemistry (4.29%). The decline in daughter shoot biomass was linked to a decrease in daughter shoot number (33.33%) by warming. However, the number of belowground buds increased by 46.43%. The results indicated that long-term summer warming reduces biomass accumulation in parent shoot by increasing both limitation of stoma and non-stoma. Consequently, the parent shoot allocates relatively more biomass to the belowground organs to maintain the survival and growth of buds. Overall, buds, as a potential aboveground population, could remedy for the cur-rent loss of parent shoot density by increasing the number of future daughter shoots if summer warming subsides.