Responses to bleaching herbicides by leaf chloroplasts of maize plants grown at different temperatures

• Published in: Journal of experimental botany 2001-04, Vol.52 (357), p.811-820
• Main Authors: Vecchia, F. Dalla, Barbato, R., La Rocca, N., Moro, I., Rascio, N.
• Format: Article
• Language: English
• Subjects: 2‐amino‐1; 4‐triazole; Agrochemicals products; aminomethane buffer saline; Amitrole; Biological and medical sciences; bovine serum albumin; BSA; carotenoid biosynthesis; Carotenoids; Chlorophylls; chlorophyll‐protein 43; chlorophyll‐protein 47; chloroplast photo‐oxidation; Chloroplasts; Chloroplasts - drug effects; Chloroplasts - ultrastructure; Chromatography, High Pressure Liquid; Corn; CP43; CP47; cyt; cytochrome; Fundamental and applied biological sciences. Psychology; HEPES; Herbicides; Herbicides - pharmacology; high performance liquid chromatography; HPLC; hydroxymethyl; Leaves; LHCII; light harvesting chlorophyll a/b‐protein complex of PSII; Microscopy, Electron; norflurazon; norflurazon (4‐chloro‐5‐(methylamino)‐2‐(α; N‐(tris‐hydroxymethyl)glycine; N‐2‐hydroxyethylpiperazine‐N′‐2‐ethanesulphonic acid; Organelles; Other agrochemicals used in plant protection (herbicides, fungicides, etc.); Oxygen - metabolism; PAGE; PBS; phosphate buffer saline; Photosynthesis; photosystem II; Phytopathology. Animal pests. Plant and forest protection; Pigments, Biological - metabolism; Plant Leaves - drug effects; Plant Leaves - ultrastructure; Plants; Plants and the Environment; Plastids; Pollution effects and side effects of agrochemicals on crop plants and forest trees. Other anthropogenic factors; Pollution effects. Side effects of agrochemicals; polyacrylamide gel electrophoresis; PSII; SDS; sodium dodecyl sulphate; TBS; Temperature; Thylakoids; Thylakoids - metabolism; Tricine; TRIS; TRIS buffer saline; Zea mays; Zea mays - drug effects; Zea mays - growth & development; α‐trifluoro‐m‐tolyl)‐3‐(2H)‐pyridazinone
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jexbot/52.357.811

The effects of growth temperature on chloroplast responses to norflurazon and amitrole, two herbicides inhibiting carotenogenesis, at phytoene desaturation and lycopene cyclization, respectively, were studied in leaves of maize plants grown at 20 °C and 30 °C in light. At the lower temperature both chemicals caused severe photo‐oxidative damage to chloroplasts. In organelles of norflurazon‐treated leaves neither carotenoids nor chlorophylls were detectable and the thylakoid system was dismantled. In organelles of amitrole‐treated leaves lycopene was accumulated, but small quantities of β‐carotene and xanthophylls were also produced. Moreover, some chlorophyll and a few inner membranes still persisted, although these latter were disarranged, lacking essential protein components and devoid of photosynthetic function. The increase in plant growth temperature to 30 °C did not change the norflurazon effects on carotenoid synthesis and the photo‐oxidative damage suffered by chloroplasts. By contrast, in organelles of amitrole‐treated leaves a large increase in photoprotective carotenoid biosynthesis occurred, with a consequent recovery of chlorophyll content, ultrastructural organization and thylakoid composition and functionality. This suggests that thermo‐modulated steps could exist in the carotenogenic pathway, between the points inhibited by the two herbicides. Moreover it shows that, unlike C3 species, C4 species, such as maize, can express a strong tolerance to herbicides like amitrole, when supplied to plants growing at their optimum temperature conditions.