Search

Popular African upland rice variety Nerica4 performs poorly under phosphorus (P) deficiency; the objective was to identify plant and soil traits likely to improve its P efficiency. Field and glasshouse experiments compared P uptake and root parameters between the popular rice genotype Nerica4, and a known P-efficient genotype, DJ123. Glasshouse experiments used fresh field soil, sterilized soil and sterilized soil resupplied with 15% fresh field soil to assess microbial effects. DJ123 had faster crown root development and higher proportions of fine roots, leading to larger root surface area (RSA). Additionally, it acquired more P per RSA, thus had more efficient roots. Higher root efficiency of DJ123 compared to Nerica4 was detected in fresh field soil, sterile soil, and sterile+resupplied soil, indicating that plant-specific factors rather than soil microbiome effects explained higher root efficiency in DJ123. In non-sterile soils both genotypes were colonized by arbuscular mycorrhizal fungi (AMF), and high expression of an AMF-induced rice P transporter gene (OsPT11) indicated the symbiosis was functional. We identified plant traits present in DJ123 such as rapid crown root development, higher proportions of fine lateral roots, as well as superior overall root efficiency that make it a promising donor to improve the performance of Nerica4 in P-deficient environments. In addition, Nerica4 appears more susceptible to growth-inhibitory effects of the soil microbiome.

Adequate zinc (Zn) in maize (Zea mays L.) is required for obtaining Zn-enriched grain and optimum yield. This study investigated the impact of varying Zn fertilizer placements on Zn accumulation in maize plant. Two pot experiments with same design were conducted to investigate the effect of soil Zn heterogeneity by mixing ZnSO4·7H2O (10 mg Zn kg−1 soil on an average) in 10–15, 0–15, 25–30, 0–30, 30–60 and 0–60 cm soil layers on maize root growth and shoot Zn content at flowering stage in experiment-1, and assessing effects on grain Zn accumulation at mature stage in experiment-2. In experiment-1, Zn placements created a large variation in soil DTPA-Zn concentration (0.3–29.0 mg kg−1), which induced a systemic and positive response of root growth within soil layers of 0–30 cm; and shoot Zn content was increased by 102 %–305 % depending on Zn placements. Supply capacity of Zn in soil, defined as sum of product of soil DTPA-Zn concentration and root surface area at different soil layers, was most related to shoot Zn content (r = 0.82, P

Drought-induced tree susceptibility is a major risk associated with climate change. Here we report how an 11-week drought affected tracheid structure, gene expression, and above- and belowground growth in 5-year-old Norway spruce trees (Picea abies) under controlled conditions. The canopy of trees subjected to severe drought had significantly less current-year needle biomass, and fewer tracheids and tracheid rows in current-year shoots compared to fully watered control trees. Belowground tissues were more strongly affected by drought than aboveground tissues. In fine roots (

Plants are widely used in soil conservation to control and prevent erosion on hillslopes and on riverbanks. Previous research has shown the mechanical root reinforcement on soil stability can be considerable. However, land and forest managers still require information and simple tools to enable them to determine how and when a species becomes effective in terms of soil stabilisation. This paper uses root length data from a trial of young New Zealand trees and shrubs to develop a simple model to account for the spatial occupancy of a planting site by roots, and by implication their potential strength contribution to soil reinforcement. It is developed by calculating root surface area in contact with the soil to obtain an effective radius of the root spread about the stem. The approach generates a set of coefficients that are unique to a species for a given site which can then be used in the generalised model to predict root site occupancy, which is taken as a proxy for when soil reinforcement is attained. This information can then be used to assess effectiveness of different species mixes in planting plans.

In this paper we examine the key elements of cluster or proteoid roots, and trace their origins back to regular root properties. By viewing the root system as being composed of two categories of surface, the high transport capacity (HTC) area, just behind the meristem, and the low transport capacity (LTC) area (the rest of the root system), based on export and import capacities, we examine root system architecture in terms of structure–function relationships, and conclude that measuring total root exudation per unit area, volume or mass will not give useful comparative data for root transport properties. Furthermore, the cluster root represents a manipulation of the HTC to LTC root surface area ratio. Increased exudation and P uptake may be no higher in individual rootlets than in other HTC regions of the root system. We also examine the transformation theory (the theory of form resulting from a series of forces, which, when altered, lead to a change, or transformation in form) as an explanation of cluster root evolution, and conclude that the cluster root requires only a change in pericycle response to depleted internal nutrient levels, with the other characteristics representing consequences stemming from the form and constraints of the root system.

Scanning electron micrographs were used to determine dimensions of hairy roots and formulae were derived for estimation of root surface area and volume. The method proved suitable for the structurally-complex proteoid roots ofLeucadendron laureolum whose surface area was 10.6×that of equivalent ‘normal’ roots on a volume basis and 15.8×on a dry weight basis.

The root systems of all plants adapt to soil conditions. One of the ways Norway spruce adapts is a regulation of absorbing root surface area, which can be viewed as an ecomorphological index of soil conditions. Minimal specific root surface area of absorbing roots of Norway spruce (28–29 m2kg−1) responds to optimal soil conditions. This was achieved at a soil bulk density of about 1.2 gcm−3.

In a solution culture study the absorption of Ca in the shoot of cucumber (Cucumis sativus L.) and various root parameters viz fresh weight, dry weight, length and surface area were measured at weekly intervals. All the root parameters were significantly correlated (p=0.01) with the amount of Ca absorbed when the concentration of Ca was such (5 meq/l) that the absorption capacity of the root membrane was fully saturated. The use of this relationship has been suggested in estimating the amount of roots developed in the soil system where identical conditions exist with respect to Ca concentration. Such estimated values have been termed as ‘equivalent root length’ or ‘equivalent root surface area’ as the case may be. P and K flux into the roots growing in the soil system have been worked out from these estimates of root parameters.

Fluxes of Ca and P through intact corn roots growing in flowing, well stirred nutrient solutions, were determined. The flux of Ca increased linearily when the Ca concentration in the nutrient solution was raised up to 250 ppm Ca. An increase in the P concentration from 0.02 ppm to 0.4 ppm P resulted in a higher Ca flux at each Ca concentration. A P concentration of about 0.15 ppm was found to be the saturation concentration above which the P flux through the roots increased only slightly. A Ca concentration range of 100 to 200 ppm had no apparent effect on the P flux. The flux through a certain unit of root surface area for both Ca and P dropped to nearly zero after 150 hours of active absorption. It is suggested that this is connected with the decrease in the specific surface area of the root with age, which is proposed to be due to the suberization which was observed microscopically.

Accumulation of Cd in the shoots of plants grown on Cd contaminated soils shows considerable variation. A previous preliminary experiment established that one major reason for this variation was the rate of Cd influx into the roots (mol Cd cm−2 root s−1). However, this experiment did not distinguish between solubilization of soil Cd on the one hand and difference in Cd uptake kinetics on the other. The main objectives of the present study were thus to characterize Cd uptake kinetics of plants continuously exposed to Cd concentrations similar to those encountered in soils. Furthermore we determined the factors responsible for differences in shoot Cd concentration such as net Cd influx, root area-shoot dry weight ratio, shoot growth rate and proportion of Cd translocated to the shoot. Maize, sunflower, flax and spinach were grown in nutrient solution with five constant Cd concentrations varying from 0 to 1.0 μmol L−1. Root and shoot parameters as well as Cd uptake were determined at two harvest dates and from these data Cd net influx and shoot growth rates were calculated. Cadmium uptake kinetics, i.e. the net Cd influx vs. Cd solution concentration followed a straight line. Its slope is the root absorbing power, α, $$ \left( {\alpha ={{{\mathrm{Cd}\;\mathrm{net}\;\mathrm{influx}}} \left/ {{\mathrm{Cd}\;\mathrm{solution}\;\mathrm{concentration}}} \right.}} \right) $$ . The α values of spinach and flax were about double that of maize and sunflower (5 × 10−6 cm s−1 vs. 2.5 × 10−6 cm s−1). Spinach and flax had a 3–5 times higher shoot Cd concentration than maize and sunflower. The difference in shoot Cd concentration was partly due to the higher Cd influx but also to a higher translocation of Cd from root to shoot and also to a slower shoot growth rate.

A method of determining the surface area of mycorrhizous conifer roots is described. The roots are cleaned from soil particles by washing, slightly dried and covered with a monolayer of plastic beads. The surface area is estimated on the basis of the weight of adhered beads.