Báo cáo lâm nghiệp: Cytokinin activity in Citrus seedlings colonized by mycorrhizal fungi

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Báo cáo lâm nghiệp: " Cytokinin activity in Citrus seedlings colonized by mycorrhizal fungi"Cytokinin activity in Citrus seedlingscolonized by mycorrhizal fungiR.K. Dixon*School of Forestry, Auburn University, Auburn, AL 36849, U.S.A. Thaxt. (Gerd. and Trappe) and G. mosseaeIntroduction (Nichol. and Gerd.) were used to inoculate seedlings using methods described by Bethen- falvay and Yoder (1981).Plants were grown in aThe level of cytokinin-like substances is glasshouse for 105 d under previously de-greater in the leaves of the vesicu- scribed culture conditions (Menge et al., 1978).lar-arbuscular mycorrhizal monocotyledon Following harvest, seedling dry weight andBouteloua gracilis compared to non- vesicular-arbuscular mycorrhizal colonization ofmycorrhizal plants (Allen et aL, 1980). inoculated and non-inoculated plants wereThis increase may be associated with measured. Seedling leaf subsamples were ana- lyzed for phosphorus content (Menge et aL,colonization of roots by vesicular-arbus- 1978).cular mycorrhizal fungi or the result of Leaf samples were collected for cytokininimproved mineral nutrition (Van Staden analysis before final harvest of seedlings. Theand Davey, 1979). The objectives of this partially purified cytokinin extracts of fully ex-research were to: 1 ) establish the pres- panded leaves were separated by high perform- liquid chromatography using proceduresence of cytokinins in leaves of Citrus ance described by Horg;an and Kramers (1979).jambhiri Lush. seedlings inoculated withvesicular-arbuscular mycorrhizal fungi;and 2) isolate cytokinins with demon-strated biological activity. Results All C. jambhiri seedlings inoculated with fungal symbionts exhibited abundant vesi-Materials and Methods cular-arbuscular mycorrhizal development after 105 d. Control seedlings were non-Five vesicular-arbuscular mycorrhizal fungi mycorrhizal. Inoculation of Citrus seed-including Glomus caledonium (Nicol. and lings with vesicular-arbuscular mycorrhi-Gerd.), G. epigaeum (Dan and Trappe), G. etu-nicatum (Becker and Gerd.), G. fasciculatum zal fungi significantly influenced total dry*’ Present address: Environmental Research Present Laboratory, U.S. Environmental Protection Agency, U.S. 200 SW 35th St.,Corvallis, OR 97333, U.S.A.weight and phosphorus content of leaves.Seedlings inoculated with G. caledonium,G. fasciculatum and G. mosseae weresignificantly larger than the non-inoculatedcontrol plants. Similarly, leaf phosphoruslevels were significantly greater in thevesicular-arbuscular mycorrhizal seed-lings compared to the non-mycorrhizalplants. vesicular-arbuscular Inoculation withmycorrhizal fungi significantly increasedcytokinin activity in leaves of C. jambhiri.Colonization by G. fasciculatum and G.mosseae resulted in a significant increasein seedling leaf cytokinin activity. Severalcytokinins, including zeatin and zeatinriboside, were detected in seedling leaves.Discussion and ConclusionThese results demonstrate the presenceof cytokinins in leaves of C. jambhiri.Endogenous cytokinin activity in C. jamb-hiri leaves has not been reported pre-viously. The cytokinin activity in leavesmay be attributable to acropetal transportfrom roots and/or regulation to cytokininoxidase enzymes (Van Staden and Davey,1979). This study established significant in cytokinin activity in leaves at-changestributable to colonization of seedlings withdifferent vesicular-arbuscular mycorrhizalsymbionts. Changes in cytokinin-li ...