Caracterização fisiológica da redução de crescimento de mudas de citros micorrizadas em altas doses de fósforo

An experiment was installed under greenhouse conditions to study growth depression in mycorrhizal citrus rootstocks at six P levels (0, 50, 100, 150, 200, and 250 mg kg-1), with and without (controls) inoculation of the arbuscular mycorrhizal fungus (AMF) (Glomus intraradices). The rootstock used was Citrus reshni Hort. Ex Tanaka, cv. Cleopatra, grown in an autoclaved, limed mixture (3:1) of a soil with low available P and washed sand. There were five replicates per treatment, in a random 6 x 2 factorial design. Six months after transplanting the seedlings, the plants were harvested and analyzed. The following characteristics were considered: plant growth, shoot dry matter, leaf area, transpiration and stomatal resistance. At the highest P levels, mycorrhizal plants presented lower dry matter and plant height values, lower leaf transpiration, and higher stomatal resistance, when compared to non-mycorrhizal plants. Therefore, growth depression of mycorrhizal citrus plants at high P levels may be related to a strong carbon sink in mycorrhizal citrus roots.