Ecological significance of light quality in optimizing plant defence

Abstract

Plants balance the allocation of resources between growth and defence to optimize fitness in a competitive environment. Perception of neighbour‐detection cues, such as a low ratio of red to far‐red (R:FR) radiation, activates a suite of shade‐avoidance responses that include stem elongation and upward leaf movement, whilst simultaneously downregulating defence. This downregulation is hypothesized to benefit the plant either by mediating the growth‐defence balance in favour of growth in high plant densities or, alternatively, by mediating defence of individual leaves such that those most photosynthetically productive are best protected. To test these hypotheses, we used a 3D functional–structural plant model of Brassica nigra that mechanistically simulates the interactions between plant architecture, herbivory, and the light environment. Our results show that plant‐level defence expression is a strong determinant of plant fitness and that leaf‐level defence mediation by R:FR can provide a fitness benefit in high densities. However, optimal plant‐level defence expression does not decrease monotonically with plant density, indicating that R:FR mediation of defence alone is not enough to optimize defence between densities. Therefore, assessing the ecological significance of R:FR‐mediated defence is paramount to better understand the evolution of this physiological linkage and its implications for crop breeding.

Stress priming, memory, and signalling in plants

“…Particular emphasis is placed on the role of chromatin organization, transcription factors, posttranslational modifications, phytohormones, and metabolites involved in stress management. Plant responses do depend not only on the plant's intrinsic capability to cope with a specific stress but also on habitat conditions and the availability of symbionts, as pointed out by Douma et al () and Mason, Jones, and Felton () in this issue.…”

“…The shade‐avoidance growth response at high plant densities may limit the resources available for defence. Douma et al () tested the relationship between plant density and defence against herbivory by a functional–structural plant model for Brassica nigra . The model shows that optimal plant‐level defence does not monotonically decrease with plant density.…”

Red-light is an environmental effector for mutualism between begomovirus and its vector whitefly

“…To cope with these environmental changes, sessile plants have evolved integrated mechanisms to respond these complex stress conditions, minimizing damages, while conserving valuable resources for growth and reproduction [ 11 – 13 ]. As an energy source and a key environmental factor, light influences plant growth, defense, and even ecological structure [ 14 , 15 ]. The perception of light signals by phytochrome photoreceptors initiates downstream signaling pathways and regulates numerous plant processes during growth and defense [ 16 ].…”

Integrating terrestrial laser scanning with functional–structural plant models to investigate ecological and evolutionary processes of forest communities

“…Recent FSPM studies have indicated that light competition reduces individual plant defence against herbivory ( de Vries et al ., 2018 , 2019 ). In addition, Douma et al (2019) , have shown that it is not only the quantity of light that contributes to plant defence, but also the quality of available light.…”