1.
Influence of fungal endophytes on plant physiology is more pronounced under stress than well-watered conditions: a meta-analysis.
Dastogeer, KMG
Planta. 2018;(6):1403-1416
Abstract
A meta-analysis of published articles shows that the influence of fungal endophytes on plant performance is dependent on plant water status. The magnitude of endophytic effects is higher in plants grown in water-limiting environments than those in adequate watering environments. The outcome of plant-endophyte interactions depends on the identity of the plant host and fungal symbionts. Water limitation often hinders plant productivity in both natural and agricultural settings. Endophytic fungal symbionts can mediate plant water stress responses by enhancing drought tolerance and avoidance, but these effects have not been quantified across plant-endophyte studies. A meta-analysis of published studies was performed to determine how endophytic fungal symbionts influence plant response under non-stressed versus water-stressed conditions. A significantly positive or neutral overall effect of fungal endophyte was noted under water-stressed conditions. In contrast, under non-stressed conditions, the overall effect of fungi on plants was mostly neutral. In general, the presence of fungal endophytes increased plant's total biomass, chlorophyll content, and stomatal conductance irrespective of water availability. In addition, plant shoot biomass, tiller density, plant height, maximum quantum yield (Fv/Fm), net photosynthesis, relative water content (RWC), amounts of ascorbate peroxidase (APX), glutathione (GSH), polyphenol oxidase (PPO), superoxide dismutase (SOD), and phenolics were significantly increased by endophyte colonisation under stressed conditions. Malondialdehyde (MDA) and hydrogen peroxide (H2O2) were reduced in endophytic plants under stress as compared with non-endophytic counterparts. Categorical analysis revealed that accumulation in plant biomass is influenced by factors such as host and fungi identity, the magnitude of which is greater under stressed than non-stressed conditions.
2.
Do arbuscular mycorrhizal fungi affect the allometric partition of host plant biomass to shoots and roots? A meta-analysis of studies from 1990 to 2010.
Veresoglou, SD, Menexes, G, Rillig, MC
Mycorrhiza. 2012;(3):227-35
Abstract
Arbuscular mycorrhizas (AM) are ubiquitous root symbioses with often pervasive effects on the plant host, one of which may be above- and belowground biomass allocation. A meta-analysis was conducted on 516 trials that were described in 90 available articles to examine whether AM colonization could result in a modification of partitioning of plant biomass in shoots and roots. It was hypothesized that alleviating plant nutrient limitations could result in a decrease of root to shoot (R/S) ratio in AM plants or, alternatively, the direction of shifts in the R/S ratio would be determined by the changes in total dry biomass. In our analysis, we considered four types of stresses: drought stress, single heavy metal stress, multiple heavy metal stress, and other potential abiotic plant stress factors. When disregarding any factors that could regulate effects, including stress status and mode of propagation, the overall AM effect was a significant modification of biomass towards shoot growth. However, the responses of stressed and clonally propagated plants differed from those of seed-grown unstressed plants. Our meta-analysis detected a considerable decline in the R/S ratio when plants were grown from seeds in the absence of abiotic stresses. Moreover, we demonstrate that additional regulators of the AM-mediated impact on R/S ratio were presence of competition from other plants, plant growth outcome of the symbiosis, growth substrate volume, experimental duration, and the identities of both plant and AM fungus. Our results indicate that a prediction of AM effects on R/S allocation becomes more accurate when considering regulators, most notably propagation mode and stress. We discuss possible mechanisms through which stress and other regulators may operate.