A comprehensive meta-analysis reveals the key variables and scope of seed defense priming

Background

When encountered with pathogens or herbivores, the activation of plant defense results in a penalty in plant fitness. Even though plant priming has the potential of enhancing resistance without fitness cost, hurdles such as mode of application of the priming agent or even detrimental effects in plant fitness have yet to be overcome. Here, we review and propose seed defense priming as an efficient and reliable approach for pathogen protection and pest management.

Methods

Gathering all available experimental data to date, we evaluated the magnitude of the effect depending on plant host, antagonist class, arthropod feeding guild and type of priming agent, as well as the influence of parameter selection in measuring seed defense priming effect on plant and antagonist performance.

Results

Seed defense priming enhances plant resistance while hindering antagonist performance and without a penalty in plant fitness. Specifically, it has a positive effect on crops and cereals, while negatively affecting fungi, bacteria and arthropods. Plant natural compounds and biological isolates have a stronger influence in plant and antagonist performance than synthetic chemicals and volatiles.

Discussion

This is the first meta-analysis conducted evaluating the effect of seed defense priming against biotic stresses studying both plant and pest/pathogen performance. Here, we proved its efficacy in enhancing both, plant resistance and plant fitness, and its wide range of application. In addition, we offered insight into the selection of the most suitable priming agent and directed the focus of interest for novel research.

Influence of polymerization methods and priming agents on the bond strength between resin luting agents and gold alloy

PURPOSE

To evaluate the influence of polymerization methods and a metal priming agent on the bond strength between gold alloy for metal ceramic restorations and dual-cure-type resin luting agents, and on the strength and hardness of the luting agents.

METHODS

A total of 154 disks cast by a gold alloy were treated with or without a metal priming agent. One of the three luting agents was applied on the disk. The luting agent was either chemically or dual-polymerized. The shear bond strength was measured both before and after thermocycling. In addition, scanning electron microscope (SEM) observation, flexural strength test, and Knoop hardness test were performed.

RESULTS

Significant differences among the luting agents were observed in terms of bond strength and flexural strength. Significant differences between chemically and dual-polymerized luting agents were observed regarding shear bond strength, flexural strength, and Knoop hardness before thermocycling. The application of the priming agent was effective only for a luting agent.

CONCLUSION

Both bond strength and flexural strength differed among three luting agents. The effect of the priming agent on bond strength differed among the luting agents. Both the bond and flexural strength of a chemically polymerized luting agent differed before or after thermocycling.

[Plant anti-herbivore defense priming: Concept, mechanisms and application.]

Plant anti-herbivore defense priming refers to the increased readiness of anti-herbivore defense after the initial exposure to a series of biotic or abiotic factors. The primed plants can respond to herbivory more quickly and strongly and thereby show enhanced resistance to insect herbivory. It is a newly recognized strategy of plant defense against insect herbivores. Insect feeding, secretion, oviposition, herbivore-inducible plant volatiles (HIPVs), beneficial microorgani-sms, certain plant nutrient elements, heavy metals and some chemical compounds have been found to be able to prime plant defense. The defense priming is highly efficient, durable, environmental friendly, and even trans-generational. This review summarized current research progress on the plant anti-herbivore defense priming in recent years, and analyzed general characteristics, priming agents and potential mechanisms involved, and proposed the future development and the perspective of practical application in the field. Moreover, the unresolved questions and the research directions in this field were also discussed. Appropriate management of plant defense priming would minimize use of insecticide and serve as an important approach of integrated pest management.