Shoot–Root Interplay Mediates Defoliation-Induced Plant Legacy Effect

Abstract

Shoot defoliation by grazers or mowing can affect root traits of grassland species, which may subsequently affect its aboveground traits and ecosystem functioning (e.g., aboveground primary production). However, experimental evidence for such reciprocal feedback between shoots and roots is limited. We grew the perennial grass Leymus chinensis–common across the eastern Eurasian steppe–as model species in a controlled-hydroponics experiment, and then removed half of its shoots, half of its roots, or a combination of both. We measured a range of plant aboveground and belowground traits (e.g., phenotypic characteristics, photosynthetic traits, root architecture) in response to the shoot and/or root removal treatments. We found the regenerated biomass was less than the lost biomass under both shoot defoliation and root severance, generating a under-compensatory growth. Root biomass was reduced by 60.11% in the defoliation treatment, while root severance indirectly reduced shoot biomass by 40.49%, indicating a feedback loop between shoot and root growth. This defoliation-induced shoot–root feedback was mediated by the disproportionate response and allometry of plant traits. Further, the effect of shoot defoliation and root severance on trait plasticity of L. chinensis was sub-additive. That is, the combined effects of the two treatments were less than the sum of their independent effects, resulting in a buffering effect on the existing negative influences on plant persistence by increased photosynthesis. Our results highlight the key role of trait plasticity in driving shoot–root reciprocal feedbacks and growth persistence in grassland plants, especially perennial species. This knowledge adds to earlier findings of legacy effects and can be used to determine the resilience of grasslands.

Root characteristics on different training methods of cucumber production in hydroponic system

“…In our experiment, successive pinching of the lateral shoots directly reduced the remaining aerial biomass (stem and leaves) by 87.7% (Table 2) and indirectly reduced the root biomass by 8.3% (Table 1). Referring to the explanations provided by Li et al (2021), the gross photosynthetic rate was markedly suppressed immediately after pinching the lateral shoots, whereas the respiration rate greatly improved. However, during the recovery process, these physiological trends were reversed, ascribing the regulation of the distribution of new photosynthate carbon in response to plant tissue damage and biomass loss (Schierenbeck et al 1994, Wang et al 2019.…”

“…Therefore, it can be said that in the PT treatment, cucumber plants used carbohydrates to generate new shoots instead of producing new roots. The same explanation was used by Li et al (2021) to justify the reduced root biomass caused indirectly by the defoliation of grasslands (Leymus chinensis). The authors reported that continuous defoliation of L. chinensis directly aff ected the under-compensatory growth of the shoot Saidi et al (2007) reported that after leaf harvesting of cowpea, photosynthates are directed toward new leaf development at the expense of being stored for grain production or being translocated to the root system for root and nodule growth.…”

Species‐specific soil legacy effects on ecosystem multifunctionality via regulating plant overyielding

“…To test whether there was an additive effect of soil legacy of mixture (M), we calculated and compared the predicted and observed values (PV and OV) of biomass from each plant type. The PV and OV values were calculated using the method of Li et al (2021). The PV of biomass was calculated by averaging the corresponding biomass in the soil legacies of grass (G), legume (L), and forb (F).…”

“…The seed source was the same as in Phase 1. In the culture room, the seeds were disinfected with 2% sodium hypochlorite (weight-volume ratio) (Li et al, 2021) and sown in pots with conditioned soil. Sterilized seeds were grown in pots with a fixed density of 18 individuals across all treatments, following a hexagonal pattern to ensure balanced competitive interactions.…”

“…To understand the effects of soil legacies and functional group richness on plant community productivity, the effect of biodiversity based on biomass was quantified using the additive partitioning method of Loreau and Hector (2001) (see Table 1) To test whether there was an additive effect of soil legacy of mixture (M), we calculated and compared the predicted and observed values (PV and OV) of biomass from each plant type. The PV and OV values were calculated using the method of Li et al (2021). The PV of biomass was calculated by averaging the corresponding biomass in the soil legacies of grass (G), legume (L), and forb (F).…”