Iron Deficiency Induced Changes in Iron Reductase Activity in Papaya Roots

• Published in: Journal of the American Society for Horticultural Science Vol. 127; no. 2; pp. 184 - 187
• Main Authors: Marler, Thomas E, Cruz, Ruben dela, Blas, Andrea L
• Format: Journal Article
• Language: English
• Published: 01.03.2002
• ISSN: 0003-1062; 2327-9788
• DOI: 10.21273/jashs.127.2.184

Four papaya ( Carica papaya L.) cultivars were cultured aeroponically or in perlite to determine the magnitude, timing, and root locality of Fe reductase induced by Fe deficiency. Five soybean [ Glycine max (L.) Merrill] lines with a known range of Fe-deficiency chlorosis scores were cultured in perlite for comparison. Speed of inducement of Fe reductase activity was determined in plants cultured without Fe for 0 to 17 days. Location of Fe reductase activity was determined by sectioning roots from the tip to 60 to 70 mm proximal to the root tip from plants cultured without Fe for 16 to 19 days. The Fe reductase system was induced in all papaya cultivars after 7 to 11 days without Fe, and activity increased through 17 days. Iron reductase activity in all papaya cultivars was comparable to the most tolerant soybean line. The zone of highest activity was the apical 10 mm of roots. These results indicate that papaya roots are highly efficient in induced Fe reductase activity. The highest activity in root tips underscores the importance of maintaining a healthy, continually growing root system with numerous growing points when culturing papaya in alkaline substrates.