Damage to leaf veins suppresses root foraging precision

Abstract

Plants typically grow in soil in which resources (e.g., water and nutrients) are distributed heterogeneously (Farley and Fitter, 1999; Wei et al., 2017), and individual plants encounter both high-and low-quality resource patches (Wei et al., 2017). Not surprisingly, plants use multiple behavioral strategies to forage for patchy resources (Cahill and McNickle, 2011). The best-studied strategy is the ability to grow more roots (biomass, length, etc.) in highnutrient patches than in low-nutrient patches (Cahill and McNickle, 2011). Such preferential allocation of root biomass is widespread among plant species (Hodge, 2004) and is generally referred to as foraging precision (Cahill and McNickle, 2011). The mechanisms underlying root foraging precision include signaling within and among organs. For example, increased root development in response to soil nitrogen involves signals sent from the shoot that coordinate overall growth and development (Ko and Helariutta, 2017). Various substances, including proteins, peptides, and phytohormones, have been detected as signaling substances and induce diverse root responses via long-distance transport through the phloem (Ko and Helariutta, 2017). In patchy soil environments, there is some evidence of a tripartite root-shoot-root signaling system (Keeble et al., 1930; Ruffel et al., 2011; Tabata et al., 2014; Ko and Helariutta, 2017), including the observation that when some roots encounter lownutrient patches, other parts of the root system can increase nitrate uptake, mediated by long-distance signaling through leaf veins (Tabata et al., 2014; Ohkubo et al., 2017). For example,

COE2 Is Required for the Root Foraging Response to Nitrogen Limitation

“…In addition, when plants are suffering from nutritional deficiencies such as nitrogen and phosphate, the foraging response of plant roots is activated to enhance the absorption of mineral nutrients from soils [15,16]. Some studies have shown that stress responses or signals from leaves induce root foraging responses [17]. However, the signal pathways coordinating the nitrogen requirement in leaves with the root foraging response are still unclear.…”

Individuality, self and sociality of vascular plants

“…Nevertheless, some secondary meristems, especially the cambium and phellogen, often retain partial autonomy in small branches and branch tips. Root branching plasticity allows roots to accomplish foraging behaviour which is critical in their difficult task of finding water and mineral nutrition [65][66][67]. In the root foraging behaviour, root apices continually evaluate, in a context-dependent manner, the amount of nutrients and integrate this information in dependency of their neighbouring plants [68].…”

“…This is the main reason that root apex organogenesis, in contrast with shoot organogenesis, is developmentally postponed and depends more on the local environmental situation [68]. Importantly, root foraging behaviour is affected by damage to shoot organs [67], implying shoot-root communication via the vascular systems is involved in both root organogenesis and root apex foraging decisions.…”

Root Foraging Behavior of Two Agronomical Herbs Subjected to Heterogeneous P Pattern and High Ca Stress

“…It has a relatively larger root system than local legume species [37], but this did not confer any priority in foraging scale. Plantago asiatica has a similar foraging precision compared to local deciduous tree species, both of which are easily interrupted by herbivores [40]. Both B. pilosa and P. asiatica roots had high foraging scale potential in karst soils, but their root morphology may be reduced by high Ca.…”