Radicle pruning by seed-eating animals helps oak seedlings absorb more soil nutrient

Although radicle pruning has well been observed in plant-animal interactions,research has not been conducted to determine how radicle pruning by seed-eating animals regulates nutrition mobilization of cotyledonary reserves and absorption of soil nutrients.We used stable nitrogen isotopes to test how acorns of early-germinating oak species(Quercus variabilis,Q.aliena,and Q.mogolica)trade off nutrients in the cotyledons and those in the soil in response to radicle pruning by seed-eating rodents.Radicle pruning by rodents resulted in root branching in the 3 early-germinating oak species.Moreover,radicle pruning increased shoot dry weight and substantially reduced the root-to-shoot ratio of oak species.Corresponding to the decreased dry weight of roots and root-to-shoot ratio,the dry weight of the remnant cotyledons was higher after radicle pruning in the 3 oak species.We provided first evidence that radicle pruning by seed-eating animals improved seedling performance of early-germinating oaks by increasing absorption of nutrients from soil.The results indicate that early-germinating oak seedlings trade off nutrition budget by altering nutrient absorption from soil and reserve mobilization from cotyledons in response to radicle pruning by seed-eating animals.Our study provided new insight into the nutrition allocation mechanism of young seedlings in response to radicle pruning by seed-eating animals,reflecting a mutualistic interaction between early-germinating oak and food-hoarding animals.