TY - JOUR
AU - MINCHIN, F, R.
AB - Abstract Soybean (Glycine max L. Merr) cv. Clarke plants inoculated with Bradyrhizobium japonicum strain RCR3407 were grown either in a greenhouse with a low irradiance (200–400)μmol m−2 s−1) or in a controlled-environment growth cabinet with a higher irradiance (600 μimol m−2 s−1). At 42 d plants were given a nitrogen-free nutrient solution containing 50 mol m−3 sodium chloride for 2 weeks and then allowed to recover from salt-stress for a further 2 weeks. Salt treatment reduced plant growth by at least half in both growth regimes, however, the controlled environment-grown (CEG) plants were five times larger than the greenhouse-grown (GG) plants in terms of dry weight and number/weight of nodules per plant, regardless of treatment. The structure of nodules, from both growth regimes, harvested at the end of the 2 week salt-stress was similar to unstressed control nodules. However, nodules harvested 1 week later from both CEG and GG plants had structural changes including degradation of bacteria in vacuoles around host cell nuclei, particularly in the outer cell layers of the infected tissue. In addition, meristematic activity was seen in the cortex of some nodules from GG plants. Young cells here contained infection threads and newly-released bacteria. Nodules harvested 2 weeks after removal of the salt-stress from CEG plants showed an apparent recovery from the stress. However, there was a very marked increase in the amount of starch in the cortex which was not seen in equivalent GG nodules. In contrast, nodules from GG plants contained many vacuolate infected cells and, consequently, a lowered bacteroid population. Further, meristematic activity was seen in a zone concentric to the infected zone, newly-formed cells contained many large infection threads and were interspersed with intercellular bacteria. The meristematic activity increased the relative volume of cortical to infected cells in these nodules. Growth conditions did not affect control nodule specific nitrogenase activity or oxygen diffusion resistance (R) and these parameters were also not altered in CEG nodules exposed to salt plus the 14 d recovery period. However, nitrogenase activity was greatly reduced, and R increased by more than eight times in equivalent GG nodules exposed to salt plus recovery. It is hypothesized that the gross morphological changes were an attempt to counter salt toxicity and/or oxygen damage under conditions of reduced photosynthate supply to the nodules due to the poor light levels in the greenhouse. However, soybean nodules supplied with adequate photosynthate were able to withstand and recover from long-term salt-stress with little alteration to their structural integrity. Soybean, sodium chloride, nitrogen fixation, light intensity, oxygen diffusion resistance This content is only available as a PDF. © Oxford University Press
TI - The Effect of Irradiance on the Recovery of Soybean Nodules from Sodium Chloride-Induced Senescence
JO - Journal of Experimental Botany
DO - 10.1093/jxb/44.6.997
DA - 1993-06-01
UR - https://www.deepdyve.com/lp/oxford-university-press/the-effect-of-irradiance-on-the-recovery-of-soybean-nodules-from-TTd7p3APAJ
SP - 997
EP - 1005
VL - 44
IS - 6
DP - DeepDyve
ER -