ISHS Acta Horticulturae 481: International Symposium on Growing Media and Hydroponics
ROOT DISCOLORATION, GROWTH AND MICRO ELEMENT UPTAKE OF CHRYSANTHEMUM IN AEROPONICS AS AFFECTED BY IRON CHELATES AND PYTHIUM |
| Authors: | C. de Kreij, S.J. Paternotte |
| Keywords: | chlorosis, DTPA, EDDHA, HEDTA, zinc uptake, manganese uptake |
| Abstract:
We conducted an experiment to determine if the addition of iron chelate EDDHA to the nutrient solution would suppress Pythium root rot of chrysanthemum grown in aeroponic culture. In a factorial design, treatments (six in total) were ‘non-inoculated’ and ‘inoculated’, both combined with Fe-DTPA (Dissolvine-D-Fe-6), Fe-HEDTA (Dissolvine H-Fe-13) or Fe-EDDHA (Dissolvine-Q-Fe-6) in Fe-concentrations of 50 μmol/l. Inoculation of the nutrient solution was with a mixture of 5 Pythium isolates (P. aphanidermatum and P. ultimum), originating from chrysanthemum that had proven to be pathogenic to chrysanthemum. Severity of Pythium incidence, measured as a brownish discoloration of the roots, was not diminished by EDDHA. Chrysanthemum cv. ‘Refla’, a variety with a high degree of susceptiblity to foliar chlorosis, had a higher fresh plant weight with Fe-EDDHA (73.5 g) than with Fe-DTPA (67.3 g) which was higher with Fe-HEDTA (58.5 g). In this variety, chlorosis was less with EDDHA than with DTPA and HEDTA. EDDHA is preferred above DTPA and DTPA above HEDTA for cv. ‘Refla’. For other varieties less susceptible to foliar chlorosis, e.g. ‘Majoor Bosshardt’ and ‘Reagan’, all three test iron chelates can be used. These results are valid for the pH used in the experiment, i.e. pH 5.5, only. Zn uptake by the plants was higher with Fe-EDDHA than with Fe-DTPA or Fe-HEDTA. This can be explained due to the nutrient levels. In the latter two cases, much Zn-DTPA and Zn-HEDTA is formed and Zn from Zn-DTPA and Zn-HEDTA is less available to the plant than Zn as a cation. Fe-EDDHA did not lower the Mn uptake of the plants as compared to Fe-DTPA. This is in contrast with the decreased Mn uptake sometimes found with the use of Fe-EDDHA. This discrepancy is likely to be due to the pH. The antagonistic effect of Fe-EDDHA on Mn uptake is only apparant at high pH and not at the pH 5.5 of the present experiment. | |
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