Plastic defence expression in plants

Abstract

Phenotypic plasticity is the ability of an organism to express different phenotypes in response to changing environments and becomes particularly obvious when plants alter their transcriptome after enemy attack. The resulting alterations affect the metabolic, chemical and morphological phenotype and cause resistance or tolerance phenomena, which allow plants to main high fitness in the presence of enemies. Volatiles released from damaged plants can be received by their neighbours or undamaged parts of the same plant to mount an adequate level of resistance and thereby add a further level of phenotypic plasticity. The induced defence responses also include attraction of the third trophic level and, thus, dramatic changes of the 'extended phenotype' of the plant, that is, its surrounding fauna. The underlying interactions are, at least partly, under the control of the plant and, thus, subject to co-evolutionary processes. Fitness costs are a common explanation for the evolution of inducible resistance expression. However, variability in the resistance phenotype can per se be beneficial, because it makes counter-adaptations by the plants' enemies more difficult. In the case of indirect defences, which are mediated by plant-carnivore mutualisms, signal reliability and reciprocal responses among phenotypically plastic partners appear necessary prerequisites for their evolutionary stabilisation. The expression of resistance and tolerance is induced by enemy attack but is also under control by abiotic factors, such as resource supply, and by biotic parameters, such as current and anticipated competition, efficiency of the expressed resistance and ontogenetic stage. All these levels of plasticity help plants to survive as sessile organisms in a rapidly changing environment and in the presence of mobile enemies.

Trait plasticity in species interactions: a driving force of community dynamics

“…However, a wide variety of organisms express phenotypic plasticity in response to biotic factors, such as induced plant responses to herbivory and induced prey responses to predators (Karban and Baldwin 1997;Tollrain and Harvell 1999;Agrawal 2001;Miner et al 2005;Heil 2010). For example, herbivory induces an increase in the number and length of protective spines on Acacia drepanolobium, which enhances the competitive ability and fitness of Acacia under grazing pressure (Young et al 2003).…”

Plant-emitted semi-volatiles shape the infochemical environment and herbivore resistance of heterospecific neighbors

“…4 Their ability to confer increased resistance has been suggested to create the plasticity plants need to survive in changing environments. 5 As plant populations are dynamically changing systems, complexly influenced by the biotic and abiotic environment, volatiles emitted by plants growing in heterogeneous associations will become intermingled. The mixture of chemicals emitted by different plants may appear chaotic, but the effects of emissions by neighboring species on the indirect defense of another may be definable.…”

The World Flora Online, Target 1 of the Global Strategy for Plant Conservation, and the Species Plantarum Programme: Flora of the World: Compatible Concepts or Mutually Exclusive Mandates?

“…Botanists of the twenty-first century: roles, challenges and opportunities It is evident that usually only the traits, which are needed currently due to the particular environmental quality, are expressed in particular individual (Heil, 2010). Changes at different levels of organization will occur only when necessary.…”