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 degrees 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 nonstoma. 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 current loss of parent shoot density by increasing the number of future daughter shoots if summer warming subsides.