Physiological responses of semiarid grasses. II.* The pattern of root growth in relation to external phosphorus concentration

Abstract

The effect of the external phosphorus concentration on the pattern of root development in mulga, Mitchell and buffel grasses was examined. During seedling and early vegetative growth, the pattern of root growth suggested that the emergence of axes, their extension and branching were coordinated in such a way that the mean rate of extension and distance between branches remained fairly constant for each component of the root system. Phosphorus deficiency did not greatly affect the length of the seminal axis or the number of its primary laterals, but resulted in a significant reduction in the length of these laterals; the length and number of nodal roots were also greatly reduced. Species differences in the pattern of root development are discussed in relation to seedling drought survival on infertile soils. *Part I, Aust. J. Agric. Res., 26: 423 (1975).

Root development of F1rice hybrid and parents as affected by nitrogen concentration of culture solution

“…The high SRL of eight grasses with low nutrient supply was reported previously (Fitter 1985). Christie and Moorby (1975) also observed that the SRL of three grasses was higher in a low P solution (0.003 mg L-I) than in a high P solution (3 mg L-I). In the present study, the same trend was found in the rice genotypes grown in the ammonium-N solution, suggesting an adaptive response to low fertility medium.…”

Root growth of Fagus sylvatica: impact of air quality and drought at a site in southern Britain

“…1). Christie (1975), showed that greater SRLs are usually due to the production of roots with a smaller diameter, suggesting that exposure to ambient pollution resulted in the production of longer, thinner roots.…”

“…Another problem is that thinner roots could be prone to rapid dehydration and loss of turgor pressure, which is essential for the maintenance of cell expansion and root elongation. No direct measurements of root diameter were made although Christie (1975), working on semi arid grasses demonstrated that high root length/weight ratios were generally characteristic of roots with a small diameter. High SRLs could also be due to roots with less densely packed cells or root cells with thinner walls.…”

“…It is generally accepted that the acquisition of water and nutrients is much more closely related to root volume or total root length, rather than dry weight (Klepper, 1987). Clearly there is a relationship between root length and root dry weight, but this may not remain constant, changing seasonally and in response to root stress (Christie, 1975;Paul & Ayres, 1986). This relationship has not been investigated for plants exposed to ambient pollution.…”

Development and Growth of Crop Root Systems

“…For example, Christie (1975) found that phosphorus deficiency for three grasses decreased the average root diameter to 85% of its value on normal plants. For example, mulga grass root radius was 0.20 mm at 3 mg L -\ phosphorus and 0.17 mm at 0.003 mg L -\ phosphorus.…”