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Netherlands Journal of Plant Pathology

, Volume 74, Supplement 1, pp 113–120 | Cite as

Shifts in disease resistance induced by growth regulators

  • O. M. van Andel
Article

Abstract

Experiments on the effect of various compounds with plant growth regulating activity led to the hypothesis that conditions inhibitory to indoleacetic acid (IAA) action or leading to a decrease in the IAA level in cucumber seedlings would be unfavourable for the development of cucumber scab, caused byCladosporium cucumerinum. Susceptibility decreased as the result of treatment with growth retardants, which cause an increase in IAA-oxidase activity in the plants, whereas application of indoleacetic acid or compounds expected to decrease the rate of oxidative breakdown of IAA in the seedlings resulted in an increase of susceptibility. Growing the plants under various periods of illumination also influenced both the susceptibility of the plants and the IAA-oxidase activity in the hypocotyl tissue.

To obtain further information about the relation between the increase in resistance and the increase in the rate of IAA oxidation, the effect of one compound, viz. L-threo-β-phenylserine (abbr. phenylserine) was studied in more detail. The rate of oxidative breakdown of IAA was increased in extracts of hypocotyls and cotyledons of plants treated with phenylserine as compared with extracts of tissue of untreated plants. Extracts of phenylserine-treated plants were found to contain a higher cofactor and/or a lower inhibitor content than those of control plants. The substances involved were not identified, but this result may indicate a shift in the concentrations of various phenols in the tissue.

The question must remain open whether a shift in the concentration of phenols some-how effected by phenylserine treatment determines both degree of susceptibility and rate of IAA oxidation independently, or whether the rate of IAA breakdown and the resulting change in IAA content in the plants is directly related to the degree of susceptibility.

Samenvatting

Proeven over het effect van verschillende verbindingen met groeiregulerende werking leidden tot de volgende hypothese: onder omstandigheden waarin de werking van indolylazijnzuur (IAZ) wordt belemmerd of het gehalte aan IAZ in de planten afneemt, wordt de ontwikkeling van vruchtvuur, veroorzaakt doorCladosporium cucumerinum, bij komkommerkiemplanten geremd. De vatbaarheid verminderde door de behandeling met verbindingen die een toename van de activiteit van IAZ-oxydase in de planten veroorzaken, terwijl behandeling met IAZ of met stoffen, waarvan verwacht mag worden dat ze de afbraak van IAZ remmen, de vatbaarheid juist verhoogde. Ook bij kweken van de planten bij verschillende belichtingsperioden namen de vatbaarheid en de activiteit van de IAZ-oxydase gelijktijdig toe, respectievelijk af.

Het verband tussen de verandering in de activiteit van IAZ-oxydase en in resistentie werd nader onderzocht aan de hand van een bestudering van het effect van L-threo-β-fenylserine (afgekort: fenylserine). Door extracten van hypocotylen en cotylen van met fenylserine behandelde planten werd IAZ sneller afgebroken dan door extracten van onbehandelde planten. Er werder aanwijzingen verkregen, dat de oorzaak hiervan een hoger gehalte aan cofactoren en/of remstoffen is, die de omzetting beïnvloeden. Er is niet vastgesteld om welke verbindingen het gaat; het is echter waarschijnlijk dat hierbij fenolen zijn betrokken.

Of een verandering in de concentratie van de verschillende fenolen zowel verant-woordelijk is voor de verandering in de mate van resistentie én voor de veranderde mate van afbraak van IAZ, dan wel of het laatstgenoemde verschijnsel en de daaruitvoortvloeiende verandering in het IAZ gehalte rechtstreeks verband houdt met de resistentiegraad kon niet worden vastgesteld.

Keywords

Indoleacetic Acid Cucumber Seedling Oxidative Breakdown Growth Regulate Activity Phenylserine 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Koninklijke Nederlandse Planteziektenkundige Vereniging 1968

Authors and Affiliations

  • O. M. van Andel
    • 1
  1. 1.Laboratory of PhytopathologyAgricultural UniversityWageningenThe Netherlands

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