Respiration and photosynthesis in oats exhibiting different levels of partial resistance to Erysiphe graminis D.c. ex Merat f. sp. avenae Marchal

Abstract

SUMM.'VRYRates of photosynthesis and respiration were measured by two methods, oxygen electTode and infrared gas analysis (IRGA), in infected and control, seedling and adult leaves of oat genotypes exhibiting different levels of partial resistance. Measurements were carried out up to 9 d after inoculation, sporulation commencing on day 5. There was no decrease in the rate of photosynthesis, except in the second leaves of one genotype, and no decrease in any of the fifth leaves relative to controls. The two methods of measuring respiration gave different results, with no consistent differences being found. Measurements by oxygen electrode, up to 6 d after inoculation, revealed that disease treatment had a significant effect on respiration in only two cases; the susceptible first leaf of one genotype and the resistant fifth leaf of another. Measurements by IRGA, up to 9 d after inoculation, did not confirm these differences, but did reveal a significant increase in respiration in the diseased fifth leaf of another resistant genotype. SHAM inhibited respiration, indicating the presence of the alternative oxidase, but there was no significant difference in its activity between diseased and control plants. Thus changes in photosynthesis and respiration previously associated with powdery mildew infection are either delayed or compensated for in oats, Photosynthetic and respiratory responses do not appear to be involved in partial resistance of oats to powdery mildew.

Local and Systemic Changes in Photosynthetic Parameters and Antioxidant Activity in Cucumber Challenged with Pseudomonas syringae pv lachrymans

“…All these interconnected events were observed in the 3rd leaves but not in the 5th leaves of the inoculated plants and could be responsible for reduced net photosynthesis rate becoming significant in the 3rd leaves with the expression of necrotic disease symptoms at 7 dai. Our results support a clear correlation between declined net photosynthesis rate and infection development described for other plant interactions with biotrophic pathogens [ 42 , 43 ]. However, the reduction in PSII efficiency and net photosynthesis rate in the 3rd leaves at 7 dai could be also attributable to senescence of the infected organ induced by hemibiotrophs as they switch from biotrophic to necrotrophic lifestyle [ 44 ].…”