Macro and Micronutrient Storage in Plants and Their Remobilization When Facing Scarcity: The Case of Drought

Abstract

Human mineral malnutrition or hidden hunger is considered a global challenge, affecting a large proportion of the world’s population. The reduction in the mineral content of edible plant products is frequently found in cultivars bred for higher yields, and is probably increased by intensive agricultural practices. The filling of grain with macro and micronutrients is partly the result of a direct allocation from root uptake and remobilization from vegetative tissues. The aim of this bibliographic review is to focus on recent knowledge obtained from ionomic analysis of plant tissues in order to build a global appraisal of the potential remobilization of all macro and micronutrients, and especially those from leaves. Nitrogen is always remobilized from leaves of all plant species, although with different efficiencies, while nutrients such as K, S, P, Mg, Cu, Mo, Fe and Zn can be mobilized to a certain extent when plants are facing deficiencies. On the opposite, there is few evidence for leaf mobilization of Ca, Mn, Ni and B. Mechanisms related to the remobilization process (remobilization of mineral forms from vacuolar and organic compounds associated with senescence, respectively) are also discussed in the context of drought, an abiotic stress that is thought to increase and known to modulate the ionic composition of grain in crops.

Evergreen Quercus aquifolioides remobilizes more soluble carbon components but less N and P from leaves to shoots than deciduous Betula ermanii at the end-season

“…Resource remobilization efficiency can be higher at low nutrient availability or in low-temperature environment (Pugnaire & Chapin 1992, Bridgham et al 1995, representing an adaptation to the less suitable habitats (Chapin 1980). A recent review (Etienne et al 2018) and a research paper (Maillard et al 2015) indicated that, during leaf senescence, N and P were always remobilized from leaves to shoots, irrespective of plant species, and environmental factors, such as drought and nutrient deficiency, modified the remobilization efficiency. Despite the importance of such processes, it is still unclear whether elevation affects remobilization of nutrients and carbohydrates, and whether this elevation-remobilization relation differs between deciduous and evergreen species.…”

Plant Nutrient Dynamics in Stressful Environments: Needs Interfere with Burdens

“…The availability of nutrients in the soil, their acquisition, assimilation, distribution/redistribution within the plants, and the nutrient balance sheets for fields can be severely disturbed by climatic stress factors [13,[24][25][26][27]. Such effects may not be restricted to the actual growing season, and may be relevant for the subsequent years(s).…”

“…Such transport processes and their regulation allow an accumulation of nutrients in harvested vegetative [16] or reproductive plant parts [17,18]. The mobility of an element or of certain forms of an element in the phloem is crucial for redistribution processes within the plant [13,19,20]. Such redistribution processes are crucial for heavy metal homeostasis [21], hyperaccumulation [22], and toxicity [11].…”

“…A balanced supply of macro-and micronutrients is essential to decrease the susceptibility of plants to biotic and abiotic stresses. Silicon-an element not belonging to the essential nutrients-plays a key role in the response of plants to biotic stresses (e.g., fungal attack) and a series of abiotic stresses such as drought or heavy metal stress [5,[11][12][13]. For example, silicon can decrease the toxic effects of heavy metals or play a protective role against fungal diseases by positively influencing the structure and function of plant cell walls [5].…”

“…Etienne et al [13] contributed a review focused on senescence of vegetative plant parts and nutrient redistribution in annual crops. Drought effects on nutrient dynamics within the shoot, including remobilization from senescing leaves and transport to reproductive structures via xylem and phloem, are discussed in this paper.…”