Plant Responses to Vegetation Proximity: A Whole Life Avoiding Shade

Abstract

In high density of vegetation, plants detect neighbors by perceiving changes in light quality through phytochrome photoreceptors. Close vegetation proximity might result in competition for resources, such as light. To face this challenge, plants have evolved two alternative strategies: to either tolerate or avoid shade. Shade-avoiding species generally adapt their development by inducing hypocotyl, stem, and petiole elongation, apical dominance and flowering, and decreasing leaf expansion and yield, a set of responses collectively known as the shade avoidance syndrome (SAS). The SAS responses have been mostly studied at the seedling stage, centered on the increase of hypocotyl elongation. After compiling the main findings about SAS responses in seedlings, this review is focused on the response to shade at adult stages of development, such as petioles of adult leaves, and the little information available on the SAS responses in reproductive tissues. We discuss these responses based on the knowledge about the molecular mechanisms and components with a role in regulating the SAS response of the hypocotyls of Arabidopsis thaliana. The transcriptional networks involved in this process, as well as the communication among the tissues that perceive the shade and the ones that respond to this stimulus will also be briefly commented.

Phenological and fitness responses to climate warming depend upon genotype and competitive neighbourhood in Arabidopsis thaliana

“…Furthermore, competition affects the timing of the reproductive transition in plants as an aspect of the shade avoidance syndrome. This syndrome is favoured under conditions of intense competition when it is more beneficial for short-lived annuals to reproduce rapidly rather than suffer resource depletion by neighbours (Donohue, Messiqua, Pyle, Heschel, & Schmitt, 2000;Dudley & Schmitt, 1996;Huber et al, 2004;McIntyre & Strauss, 2014;Roig-Villanova & Martinez-Garcia, 2016;Schmitt, Stinchcombe, Heschel, & Huber, 2003;Takeno, 2016). Thus, high ratios of red:far-red wavelengths characteristic of foliage shade cause A. thaliana to flower early (Devlin, Halliday, Harberd, & Whitelam, 1996;Donohue et al, 2000;Dorn, Pyle, & Schmitt, 2000;Franklin, 2008;Franklin & Whitelam, 2005;Halliday, Koornneef, & Whitelam, 1994;Mullen, Weinig, & Hangarter, 2006).…”

Shade Promotes Phototropism through Phytochrome B-Controlled Auxin Production

“…Photoreceptor crosstalk also occurs during shade avoidance and phototropism, two growth responses enabling plants to maximize photosynthesis in lowlight conditions [4,5]. Vegetative shade is detected by phytochromes and cryptochromes because light under a canopy is characterized by a low R/FR ratio and low blue light [5,6]. Shade responses are inhibited in the presence of UV-B by the UVR8 photoreceptor [7,8].…”

Variation in maize chlorophyll biosynthesis alters plant architecture

“…The shared biosynthetic origins of chlorophyll and bilin chromophores required for phytochrome assembly (Frankenberg and Lagarias 2012) was explored as a possible source of increase in total plant height observed in Oy1-N1989/+ mutants modified by vey1 B73 . Low R/FR ratio is indicative of shade in the plant canopy and elicits a shade avoidance syndrome via phytochrome signaling (Chen et al 2004;Pierik and De Wit 2014;Roig-Villanova and Martínez-García 2016;Ortiz-Alcaide et al 2019). If a mutation in oy1 perturbs tetrapyrrole biosynthesis, a reduction in the pool of functional phytochrome should increase mesocotyl length and plant height and reduce the number of days to reproductive maturity as had been reported previously in the elongated mesocotyl1 (elm1) maize mutant which is defective in chromophore synthesis and has reduced phytochrome levels (Sawers et al 2002).…”