Search

Leaf photosynthesis models are used extensively in photosynthesis research and are embedded in many larger scale models. Typical photosynthesis models simplify light intensity as the integrated intensity over the 400-700 nm waveband (photosynthetic active radiation, PAR). However, far-red light (700-750 nm, FR) also drives photosynthesis when supplied in addition to light within the PAR spectrum. Currently, it is unknown how much far-red light contributes to carbon assimilation under various spectral light conditions. We developed a combined experimental and computational method to quantify FR stimulation. Gas-exchange parameters and incident light spectra were measured simultaneously and analysed with wavelength-dependent modelling of light harvesting. Hereto, separate excitation of Photosystem I and Photosystem II was calculated from incident light spectra. The effect of FR supplementation on photosynthesis was subsequently modelled and expressed as a single parameter ρ. We tested our method on Solanum dulcamara, Lactuca sativa and Phaseolus vulgaris under various light conditions. Results show consistent ρ-values across a range of FR levels. Our method provides an approach to consistently quantify the effect of FR stimulation on photosynthesis and harmonise the interpretation of photosynthesis measurements under different light regimes, for example in (experimental) setups with artificial FR supplementation or in canopies., (© 2024 The Author(s). Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Plants use light as a resource and signal. Photons within the 400-700 nm waveband are considered photosynthetically active. Far-red photons (FR, 700-800 nm) are used by plants to detect nearby vegetation and elicit the shade avoidance syndrome. In addition, FR photons have also been shown to contribute to photosynthesis, but knowledge about these dual effects remains scarce. Here, we study shoot-architectural and photosynthetic responses to supplemental FR light during the photoperiod in several rice varieties. We observed that FR enrichment only mildly affected the rice transcriptome and shoot architecture as compared to established model species, whereas leaf formation, tillering and biomass accumulation were clearly promoted. Consistent with this growth promotion, we found that CO 2 -fixation in supplemental FR was strongly enhanced, especially in plants acclimated to FR-enriched conditions as compared to control conditions. This growth promotion dominates the effects of FR photons on shoot development and architecture. When substituting FR enrichment with an end-of-day FR pulse, this prevented photosynthesis-promoting effects and elicited shade avoidance responses. We conclude that FR photons can have a dual role, where effects depend on the environmental context: in addition to being an environmental signal, they are also a potent source of harvestable energy., (© 2024 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Plants that grow in high density communities activate shade avoidance responses to consolidate light capture by individuals. Although this is an evolutionary successful strategy, it may not enhance performance of the community as a whole. Resources are invested in shade responses at the expense of other organs and light penetration through the canopy is increased, allowing invading competitors to grow better. Here we investigate if suppression of shade avoidance responses would enhance group performance of a monoculture community that is invaded by a competitor. Using different Arabidopsis genotypes, we show that suppression of shade-induced upward leaf movement in the pif7 mutant increases the pif7 communal performance against invaders as compared to a wild-type canopy. The invaders were more severely suppressed and the community grew larger as compared to wild type. Using computational modelling, we show that leaf angle variations indeed strongly affect light penetration and growth of competitors that invade the canopy. Our data thus show that modifying specific shade avoidance aspects can improve plant community performance. These insights may help to suppress weeds in crop stands., (© 2020 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Plants growing at high densities interact via a multitude of pathways. Here, we provide an overview of mechanisms and functional consequences of plant architectural responses initiated by light cues that occur in dense vegetation. We will review the current state of knowledge about shade avoidance, as well as its possible applications. On an individual level, plants perceive neighbour-associated changes in light quality and quantity mainly with phytochromes for red and far-red light and cryptochromes and phototropins for blue light. Downstream of these photoreceptors, elaborate signalling and integration takes place with the PHYTOCHROME INTERACTING FACTORS, several hormones and other regulators. This signalling leads to the shade avoidance responses, consisting of hyponasty, stem and petiole elongation, apical dominance and life cycle adjustments. Architectural changes of the individual plant have consequences for the plant community, affecting canopy structure, species composition and population fitness. In this context, we highlight the ecological, evolutionary and agricultural importance of shade avoidance., (© 2020 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Plants experience a decrease in the red:far-red light ratio (R:FR) when grown at high planting density. In addition to eliciting the shade avoidance response, low R:FR also enhances plant susceptibility to pathogens via modulation of defense hormone-mediated responses. However, other mechanisms, also affected by low R:FR, have not been considered as potential components in FR-induced susceptibility. Here, we identify FR-induced accumulation of leaf soluble sugars as a novel component of FR-induced susceptibility. We observed that phytochrome inactivation by FR or phytochrome B mutation was associated with elevated leaf glucose and fructose levels and enhanced disease severity caused by Botrytis cinerea. By experimentally manipulating internal leaf sugar levels, we found that the FR-induced susceptibility in tomato was partly sugar-dependent. Further analysis revealed that the observed sugar accumulation in supplemental FR occurred in a jasmonic acid (JA)-dependent manner, and the JA biosynthesis mutant def1 also displayed elevated soluble sugar levels, which was rescued by exogenous methyl jasmonate (MeJA) application. We propose that the reduced JA responsiveness under low R:FR promotes disease symptoms not only via dampened induction of defense responses, but also via increased levels of soluble sugars that supports pathogen growth in tomato leaves., (© 2020 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Plants use photoreceptor proteins to detect the proximity of other plants and to activate adaptive responses. Of these photoreceptors, phytochrome B (phyB), which is sensitive to changes in the red (R) to far-red (FR) ratio of sunlight, is the one that has been studied in greatest detail. The molecular connections between the proximity signal (low R:FR) and a model physiological response (increased elongation growth) have now been mapped in considerable detail in Arabidopsis seedlings. We briefly review our current understanding of these connections and discuss recent progress in establishing the roles of other photoreceptors in regulating growth-related pathways in response to competition cues. We also consider processes other than elongation that are controlled by photoreceptors and contribute to plant fitness under variable light conditions, including photoresponses that optimize the utilization of soil resources. In examining recent advances in the field, we highlight emerging roles of phyB as a major modulator of hormones related to plant immunity, in particular salicylic acid and jasmonic acid (JA). Recent attempts to manipulate connections between light signals and defence in Arabidopsis suggest that it might be possible to improve crop health at high planting densities by targeting links between phyB and JA signalling., (© 2017 John Wiley & Sons Ltd.)

Although plants are sessile organisms, they can modulate their phenotype so as to cope with environmental stresses such as herbivore attack and competition with neighbouring plants. Plant-produced volatile compounds mediate various aspects of plant defence. The emission of volatiles has costs and benefits. Research on the role of plant volatiles in defence has focused primarily on the responses of individual plants. However, in nature, plants rarely occur as isolated individuals but are members of plant communities where they compete for resources and exchange information with other plants. In this review, we address the effects of neighbouring plants on plant volatile-mediated defences. We will outline the various roles of volatile compounds in the interactions between plants and other organisms, address the mechanisms of plant neighbour perception in plant communities, and discuss how neighbour detection and volatile signalling are interconnected. Finally, we will outline the most urgent questions to be addressed in the future., (© 2014 John Wiley & Sons Ltd.)

The slow gas diffusion rate in flooded soil not only causes oxygen deficiency, but also favours the accumulation of ethylene in root systems to concentrations that may strongly affect root elongation. Previously published experiments showed that root elongation in rice is much less strongly inhibited by ethylene than in some other species less well adapted to wet conditions. Rice roots have also been reported to produce abnormally little ethylene. We tested if these traits are typical of wetland species and are thus likely to be widespread adaptive traits. Comparisons using 14 species indicated that insensitivity to the inhibiting effects of ethylene on root elongation is unlikely to be a common feature of temperate wetland species. However, resistance to longitudinal gas diffusion within roots of wetland species, which largely depends on diameter and the presence of gas-filled channels, was found to be less than in non-wetland species. We show that this can help maintain low internal ethylene concentrations by venting accumulated gas to the shoot and atmosphere.