Plant responses to arbuscular mycorrhizae under elevated temperature and drought

Aims Climate change is predicted to cause both increased temperatures and changes in precipitation,leading to more severe droughts in some areas.How these changes will affect plant growth may depend in part on biotic context.Most vascular plants form symbiotic rela-tionships with arbuscular mycorrhizal fungi(AMF),root symbionts that provide soil nutrients to plants in exchange for carbohydrates,which may reduce the effects of environmental stresses on plants.We investigated if AMF modified temperature and drought effects on plant growth,fitness and defenses against herbivory.Methods We manipulated AMF presence,temperature and water availability on bell pepper plants(Capsicum annuum L.)in a field setting to measure plant growth and fitness responses.In a growth chamber experiment,we also investigated if AMF influenced insect herbi-vores feeding on plants at elevated temperatures.Important findings Drought consistently reduced plant growth,and AMF did not change drought impacts.However,with sufficient water,AMF tended to benefit plant growth and flower production(but not fruit production)compared to non-mycorrhizal plants.In the growth chamber,temperature and AMF influenced plant protein and phos-phorus contents,but not defensive chemistry or herbivore perfor-mance.Thus,AMF may ameliorate the effects of temperature stress due to climate change on plants by increasing growth and nutrient content,but these effects do not extend to the constitutive herbivory defenses examined here.

How do belowground organisms influence plant-pollinator interactions?

Aims The majority of angiosperms are pollinated by animals,and this interaction is of enormous importance in both agricultural and natural systems.Pollinator behavior is influenced by plants’floral traits,and these traits may be modified by interactions with other community members.In recent years,knowledge of ecological linkages between above-and belowground organ-isms has grown tremendously.Soil communities are extremely diverse,and when their interactions with plants influence floral characteristics,they have the potential to alter pollinator attrac-tion and visitation,but plant-pollinator interactions have been neglected in studies of the direct and indirect effects of soil organism-root interactions.Here,we review these belowground interactions,focusing on the effects of nitrogen-fixing bacteria,arbuscular mycorrhizal fungi and root-feeding herbivores,and their effects on floral traits and pollinators.Further,we identify gaps in our knowledge of these indirect effects and recommend promising directions and topics that should be addressed by future research.Important Findings Belowground organisms can influence a wide variety of floral traits that are important mediators of pollinator attraction,including the number and size of flowers and nectar and pollen production.Other traits that are known to influence pollinators in some plant species,such as floral volatiles,color and nectar composition,have rarely or never been examined in the context of belowground plant interac-tions.Despite clear effects on flowers,relatively few studies have measured pollinator responses to belowground interactions.When these indirect effects have been studied,both arbuscular mycorrhi-zal fungi and root herbivores were found to shift pollinator visitation patterns.Depending on the interaction,these changes may either increase or decrease pollinator attraction.Finally,we discuss future directions for ecological studies that will more fully integrate below-ground ecology with pollination biology.We advocate a multilevel approach to these questions to not only document indirect effect pathways between soil interactions and pollination but also iden-tify the mechanisms driving changes in pollinator impacts and the resultant effects on plant fitness.A more thorough understanding of these indirect interactions will advance ecological theory and may inform management strategies in agriculture and conservation biology.