pH above 6.0 reduces nodulation in Lupinus species

Abstract

Lupinus angustifolius and Lupinus pilosus differ substantially in root growth in response to high solution pH with L. angustifolius showing much greater sensitivity to pH above 6. This study examined the effect of pH above 6 on nodulation of these two species in buffered solution. Shoot weight and root weight and length in L. pilosus was not significantly affected by pH, whereas the growth of shoots and roots of L. angustifolius was markedly impaired by increasing pH. Total root length, the number of lateral roots, and the length of individual lateral roots were greatly decreased, resulting in decreased uptake of iron and phosphorus. In addition, L. angustifolius had a higher internal requirement for iron than L. pilosus. A solution pH above 6 decreased the number of nodule initials and nodules similarly in both species but decreased nodule mass much more in L. angustifolius. The effect of high pH on nodule formation occurred prior to that on host shoot growth. High pH also decreased nitrogen concentration and content in both species but to a greater extent for L. angustifolius. The results suggested that pH above 6 has a specific effect in the impairment of nodulation in lupins.

Soil acidity in relation to groundnut-Bradyrhizobium symbiotic performance

“…high pH. They found a similar effect with lupins, which showed reduced nodulation at pH above 6.0 (Tang and Robson, 1993). Experiments with beans (Phaseolus vulgaris) showed that nodulation and growth was much improved when one or both of the symbionts were acid tolerant (Vargas and Graham, 1988).…”

“…To state that nodulation is reduced at high pH (compare Tang and Robson, 1993), rather than increased at low pH, is less likely, because the plants were growing optimally at the higher pH (6.5), which would lead to the expectation that nodulation, too, is optimal at that (higher) pH.…”

Influence of increasing bicarbonate concentrations on plant growth, organic acid accumulation in roots and iron uptake by barley, sorghum, and maize

“…High pH per se can inhibit root and shoot growth of some sensitive plants such as some Lupinus species (Bertoni et al, 1992;Tang and Robson, 1993). In the present experiment, however, the pH of the nutrient solution of the control plants (without bicarbonate) was also kept around 8.0.…”

GsTIFY10, a novel positive regulator of plant tolerance to bicarbonate stress and a repressor of jasmonate signaling

“…-PPase can be induced by bicarbonate stress (Fushimi et al 1994;Liu et al 2004). These enzymes play major roles in intracellular pHc regulation, aiding plant cells in coping with the potential acidification of the cytoplasm under environmental stress (Davies 1986;Tang and Robson 1993). GsTIFY10 may regulate plant bicarbonate stress tolerance by inducing the high expression of bicarbonate defense genes, such as NADP-ME and H ?…”