ZELENA E., ZELENY F, WONISCH A. & TAUSZ M. 2011. Effect of sulfur nutrition on glutathione content in sugar beet plants in relation with aphids infestation. Phyton (Horn, Austria) 50 (2): 319-327, with 3 figures. The effects of sulfur (S) supply combined with nitrogen (N) on plant growth and biosynthesis of glutathione (GSH) in relation with aphids infestation were studied in young sugar beet (Beta vulgaris) plants infested with black bean aphids (Aphis fabae). Both nutrients applied separately stimulated growth of leaves but their effects were amplified when applied together. Single N fertilization enhanced significantly reproduction of aphids, addition of S reduced this effect to about 30 %. The contents of GSH in leaves on variants without S were very low (about 5 nmol/g FW) and manifold increased when S was added (up to about 550 nmol/g FW in middle youngest leaves). Sulfur supplied plants had about 5 times more GSH in youngest leaves than in oldest. The positive effect of S on resistance of plants to aphids manifested itself only in sugar beet supplied with N. We suspect GSH may function in prevention of toxic saliva action of aphids on metabolism of nitrogen in host plant and thus influence the quality of their food.
The inhibitory effect of light on the growth of plantscorrelates with a decrease of free IAA content in their tissues andmight be mediated through changes of IAA metabolism. In different partsof Zea mays L. seedlings (roots, mesocotyls and coleoptiles)that respond to light with a different growth rate, the effect of lighton the formation of IAA metabolites was examined in feeding experimentswith 14C-IAA. In all tissues, IAA was taken up andmetabolised mainly into six compounds, four of them were tentativelyidentified as IAA-1-O-glucose (IAGlc), IAA-myo-inositol, indoleacetamide and IAA-aspartate (IAAsp). IAA was metabolised most slowly inthe roots. In coleoptiles and mesocotyls, IAGlc was the most abundantmetabolite, except for mesocotyls in the light. In roots, a relativelylarge amount of IAA was also metabolised into IAAsp. Light stimulatedthe rate of IAA metabolism in all tissues, but its effect on theconversion of IAA was exceptionally high in mesocotyls. In mesocotyltissue the conversion into IAAsp was greatly stimulated by light.Conversely, the content of IAGlc in mesocotyls was decreased by light.Since light inhibited mesocotyl growth significantly and specifically,it is possible that the high capacity of mesocotyls to synthesise IAAspin the light may have caused a depletion of free IAA, which then led toan inhibition of growth. In mesocotyls from the light-grown plants IAAconjugated into IAGlc was probably used for IAAspbiosynthesis.
Carbon 14-labelled indole-3-acetic acid (IAA) was fed to segments of shoots of Zea mays seedlings grown in light or dark to find the effect of light on IAA metabolism. The seedling parts coleoptile, with enclosed leaf, and mesocotyl were also used to examine differences in IAA metabolism between tissue types. The rate of metabolite formation as a function of time ranging from 1 to 12 hours was determined. Light did not significantly influence the amount of IAA taken up, but significantly increased its rate of metabolism and greatly increased the content of amide conjugates formed. There were also differences in metabolism depending on tissue type. In all tissues, IAA was metabolized mainly into six compounds. Four were tentatively identified as IAA-glucose (IAGlc), IAA-myo-inositol} (IAInos), indole acetamide (IAAm) and IAA-aspartic acid (IAAsp). 1-O-IAA-D-glucose (1-O-IAGlc) was the first conjugate formed and, except for mesocotyls in the light, it was the most abundant conjugate in maize tissue. In mesocotyl tissue the conversion of IAA into IAAsp was greatly stimulated by light, and the biosynthesis of IAAsp exceeded that of IAGlc. Since light strongly inhibited the growth of the mesocotyl, it is possible that the stimulation of IAAsp synthesis by light causes depletion of free IAA with resultant inhibition of mesocotyl growth.
The influence of indole-3-acetylaspartic acid (IAAsp) on rooting of stem cuttings from bean plants (Phaseolus vulgaris L.) of different ages, cultivated at different temperatures (17°, 21° and 25°C) was studied and compared to that of indole-3-acetic acid (IAA). At a concentration of 10−4 M, IAAsp only nonsignificantly stimulated adventitious root formation, approximately to the same level as IAA in all treatments. IAAsp at 5×10−4 M further enhanced rooting, by up 200% of control values, with little influence of temperature conditions and stock plant age. This concentration of IAA usually stimulated rooting more than the conjugate. The largest differences between the effects of IAAsp and IAA occured at the highest cultivation temperature of 25°C where stock plant age also influenced the response. The number of roots produced in comparison with the control, was enhanced from 350% on cuttings from the youngest plants to more than 600% on cuttings from the oldest. In contrast to the conjugate, 5×10−4 M IAA induced hypocotyl swelling and injury of the epidermis at the base of cuttings, in all treatments.
D,L-indol-3-yllactie acid was applied at concentrations 0.2 – 20 mg 1-1 (10-6–10-4M) to the roots of 3-d-old intact maize seedlings grown in the dark and in the light. By day 3 after application, ILA at lower concentrations (0.2–1 mg l-1) caused slight increase in the mass of etiolated plants, mainly roots. Shoot and root length was not increased. ILA at concentrations equal to, or greater than, 2 mg 1-1 reduced the length of the main roots and from 10 mg 1-1 on also the length of the shoots. In contrast, root mass was decreased by higher ILA concentrations to a lesser extent than shoot mass. The response to ILA application of etiolated seedlings differed from that of the seedlings grown in the light only at 20 mg 1-1. The inhibitory effect was more pronounced in the case of quickly growing etiolated plants.
The effect of 0.1% Metation E 50 (fenitrothion) and Fosfotion 50 (malathion) on the level of total nitrogen and that of free amino acids was investigated in juvenile and mature leaves of apple seedlings in the course of six days following treatment. Fosfotion affected both nitrogen and amino acid content to a higher degree than Metation. Fosfotion increased the total nitrogen content in all leaves, but Metation induced the change only in the leaves which were at the end of the logarithmic growth phase at the time of treatment. The level of amino acids increased on the whole, with the exception of a temporary decline in the youngest leaves as well. The treatment with both insecticides affected most the content of amides: the greatest decrease of glutamine occurred in young leaves, the highest increase in asparagine content was recorded in both juvenile and mature leaves.
