Does the root to shoot ratio show a hormetic response to stress? An ecological and environmental perspective

Abstract

Root/shoot (R/S) ratio is an important index for assessing plant health, and has received increased attention in the last decades as a sensitive indicator of plant stress induced by chemical or physical agents. The R/S ratio has been discussed in the context of ecological theory and its potential importance in ecological succession, where species follow different strategies for above-ground growth for light or below-ground competition for water and nutrients. We present evidence showing the R/S ratio follows a biphasic dose-response relationship under stress, typical of hormesis. The R/S ratio in response to stress has been widely compared among species and ecological succession classes. It is constrained by a variety of factors such as ontogeny. Furthermore, the current literature lacks doseresponse studies incorporating the full dose-response continuum, hence limiting scientific understanding and possible valuable application. The data presented provide an important perspective for new-generation studies that can advance current ecological understanding and improve carbon storage estimates by R/S ratio considerations. Hormetic response of the R/S ratio can have an important role in forestry for producing seedlings with desired characteristics to achieve maximum health/productivity and resilience under plantation conditions.

Comparative Study of Growth, Cadmium Accumulation and Tolerance of Three Chickpea (Cicer arietinum L.) Cultivars

“…The ratio of the root to the shoot (R/S) had been received greater attention in the last few decades and used as an indicator to evaluate the overall health of the plant in environmental stress conditions [56]. If a plant has a high R/S ratio, it will absorb more nutrients from their surroundings and thus increase the above-ground biomass as well as increasing the adaptability and tolerance in stress medium.…”

Ozone will remain a threat for plants independently of nitrogen load

“…Hence, it may be postulated that N deposition is not expected to alter the effect of O 3 on root, shoot and total biomass in the coming future. This is the case for shoot/root as well, the results of which suggest there was no synergistic or antagonistic effect on the allocation of photosynthates between elevated O 3 and N addition (Agathokleous, Belz, et al, ).…”

“…In particular, low N addition can positively affect plant physiological performance and growth (Díaz-Álvarez, Lindig-Cisneros, & de la Barrera, 2015;Möhl et al, 2019;Sun et al, 2018), which is opposite to those of high N addition (Díaz-Álvarez et al, 2015;Sun et al, 2018). This biphasic dose-response pattern (Agathokleous, 2018;Agathokleous, Belz, Kitao, Koike, & Calabrese, 2019) may be the reason that previous examinations of whether N addition alters the effects of O 3 on plants could not lead to a consistent conclusion . Hence, in this first meta-analysis, testing whether N addition alters O 3 effects on plants, we also attempted to account for the biphasic dose-response The larger reduction in root biomass by elevated O 3 in the presence of high N addition than in the presence of low or no N addition (for all elevated O 3 levels and N addition levels) suggests that net primary productivity may decrease in a world with concurrent elevated O 3 and high N addition.…”

Effects of soil nutrient availability and ozone on container-grown Japanese larch seedlings and role of soil microbes

“…The fact that EOZ decreased stem diameter but did not reduce stem height may indicate an altered stem shape with potentially higher susceptibility of larches to other stressors such as strong winds (Agathokleous et al 2017;Watanabe et al 2013). Interestingly, EOZ increased the root length in spite of lower A 390 , an observation that may indicate that EOZ-induced stress was modest rather than adverse (Agathokleous et al 2019).…”