Allocation Of Mineral Nutrients Research Articles

Drought Differently Modifies Tolerance and Metal Uptake in Zn- or Cu-Treated Male and Female Salix × fragilis L.

The aim of this study was to determine the tolerance to metals (Zn, Cu) and drought of male and female Salix × fragilis L. under isolated and combined treatments, and to assess the metal uptake and profiling of metabolic plant responses. The 14-day experiment was performed in a hydroponic system, and metals were applied at 1.5 mM in a Knop’s solution. Drought simulation was achieved by adding sorbitol at a moderate level (200 mM). Isolated Zn treatment enhanced plant growth, more pronouncedly in females. Equimolar Cu treatment caused diverse reactions, and females exhibited significantly higher tolerance. Male specimens were less tolerant to isolated drought and to combined drought and metal presence. The highest contents of Cu and Zn were found in roots, compared to the aboveground tissues (wooden rods and leaves), of both female and male metal-treated plants. Simultaneously applied drought limited Zn accumulation in roots and elevated its translocation to leaves while increasing Cu accumulation, predominantly in females showing higher tolerance. Both isolated and combined drought and metals reduced leaf water content, caused the allocation of mineral nutrients (Ca, Mg, K, and Na), and affected metabolism in a stressor-specific and sex-dependent manner. For males, Cu accumulation in the leaves was significantly correlated with the majority of metabolites, while for both sexes, kaempferol and salicylic acid were strongly correlated, indicating their role in tolerance against the metal. The obtained results are an excellent starting point for the practical use of male and female Salix × fragilis L. in areas heavily polluted with Cu or Zn and exposed to drought, for the purpose of their recultivation.

Distribution of mineral nutrient from nodal roots of Trifolium repens: Genotypic variation in intra‐plant allocation of 32P and 45Ca

To assess genotypic variability in nutrient supply of shoot branches, the distribution of 32P and 45Ca exported from a source nodal root (24‐h uptake period) was measured within a genotype of a large‐leaved (Kopu) and a small‐leaved (Tahora) cultivar of Trifolium repens. Source‐sink relationships of plants were modified by root severance, defoliation, and shade treatments. In control plants of both genotypes distribution of 32P and 45Ca closely followed the pathways that could be predicted from the known phyllotactic constraints on the vascular system. As such there was little allocation of radioisotopes (3.1% and 2.5% of exported 32P and 45Ca, respectively) from the source root to branches on the apposite side of the parent axis (far‐side branches). However, genotypic differences in nutrient allocation were apparent, when treatments were imposed to alter intra‐plant source‐sink relationships. In the large‐leaved genotype, the imposed treatments had minor effects on the allocation to far‐side branches: whereas, in the small‐leaved genotype, root severance and defoliation treatments increased lateral transport to far‐side branches to 30% (32P) and 10% (45Ca) of exported radioisotopes. Genotypes with low (8–9) and high (12–13) numbers of vascular bundles were selected from within the large‐leaved cultivar. Distribution of 32P was then measured after plants had been pre‐treated by removal of all far‐side roots two days prior to labelling. Genotypes with low vascular bundle number allocated 20% and those with high vascular bundle number 3.2% of exported 32P to far‐side branches. It was concluded (1) that genotypic variation exists within T. repens for potential to alter intra‐plant allocation of mineral nutrients, in response to treatments that modify source‐sink relationships within plants; and (2) that this variation is correlated with differences among genotypes in the organisation of the vasculature of their stolons.

Distribution of phosphorus and calcium from nodal roots of Trifolium repens: the relative importance of transport via xylem or phloem

summaryThe intra‐plant distribution of radioactive phosphorus (32P) and calcium (45Ca) exported from a single nodal root of Trifolium repens (white clover) was measured to ascertain if initial allocation of radioisotopes via the xylem was significantly altered over time by redistribution via the phloem. The radioisotopes were simultaneously supplied in a 2 h pulse which was followed by supply of non‐radioactive nutrient solution until harvest 3, 6, 9, 21 or 72 h after the start of labelling. By the end of the 3 d experimental period net export from the source root was 94 % total absorbed 45Ca but only 56 % of 32P. After movement through the stolon of the parent axis, main sinks for both nutrients were the leaf and the branch at the second node distal to the source root (64 and 30 % of total absorbed 45Ca and 32P respectively after 72 h). Very little of either radioisotope moved into branches located along the stolon of the parent axis, on the side opposite to the source root (1 and 2% of total absorbed 45Ca and 32P respectively after 72 h). This evidence, along with knowledge of the vascular architecture of the genotype, indicated that the allocation of mineral nutrients was determined chiefly by the vascular links between the source root and sink organs rather than sink size or proximity to the source root. Data indicated that some distribution of 32P occurred via the phloem but that it was quantitatively small in relation to allocation via the xylem both in the short (3 h) and medium (72 h) terms.

Canopy Nutrient Allocation in Relation to Incident Light in the Tropical Fruit Tree Borojoa patinoi (Cuatr.)

The relationship of incident photosynthetically active radiation (PAR) and mineral nutrient allocation was evaluated in canopies of Borojoa patinoi (Cuatr.) growing in the Chocó rainforest of Colombia, South America. Allocation of P in the canopy was positively correlated with incident PAR, principally because of increased leaf frequency (number of leaves per unit volume of canopy) brought about by local branching, with a smaller contribution from increased specific leaf weight (SLW, leaf dry weight per unit leaf area). The chemical fractionation of P within leaves did not respond to incident PAR. Canopy N allocation also was positively correlated with incident PAR because of increased leaf frequency and SLW. The N partitioning to soluble protein rather than chlorophyll was positively correlated with incident PAR. The allocation of K, Ca, Mg, S, Mn, and Cu also was positively correlated with incident PAR primarily because of increased leaf frequency and secondarily because of increased SLW. The area of individual leaves and the concentration of nutrients in leaf dry weight were not important in determining nutrient allocation responses to incident PAR. Our observations suggest that leaf frequency caused by local branching, followed by changes in SLW, are the primary determinants of canopy nutrient allocation in this tropical fruit tree.

Mineral Nutrient Allocation in Seeds and Shoots of Twelve Chionochloa Species in Relation to Soil Fertility

L'allocation de la biomasse de huit elements mineraux est etudiee dans les racines et les graines de douze especes de Chionochloa de Nouvelle Zelande.