Physiological responses of hawthorn (Crataegus persica Pojark.) and quince (Cydonia oblonga Mill.) rootstocks to bicarbonate-induced iron deficiency in nutrient solution

摘要

Hawthorn (Crataegus persica Pojark.) is used as a quince (Cydonia oblonga Mill.) rootstock in order to reduce the severity of iron (Fe) chlorosis in quince orchards in alkaline calcareous soils in central Iran. This study was conducted to investigate physiological responses of Fe-chlorosis resistant hawthorn and Fe chlorosis-sensitive quince cultivars to Fe-deficiency and different levels of HCO3 - (5, 10, 15, and 20 mM NaHCO3), in the presence or absence of 0.5 g CaCO3 L-1 in a CO2-buffered pH 7.8 nutrient solution containing 50 mu M Fe(III)-EDTA. A separate set of two free-bicarbonate controls containing deficient [5 mu M Fe(III)-EDTA] and sufficient [50 mu M Fe(III)-EDTA] Fe concentrations was also used. Chlorosis symptoms appeared on the rootstocks exposed to HCO3 - and in the 5 mu M Fe(III)-EDTA treatment. In response to HCO3 - -induced Fe deficiency, hawthorn roots released high amounts of H+ and phenolic compounds to the surrounding medium, while no such response was observed in quince. The higher resistance to bicarbonate of hawthorn was also related with a higher root activity of the ferric chelate reductase (FCR), associated to a higher Fe(OH)(3) solubilization. Accordingly, hawthorn seedlings in the HCO3 - -induced Fe deficiency had higher leaf and root Fe concentrations in comparison to those in the direct Fe deficiency. The addition of CaCO3, in general, had no or small effect on the root release of H+ and phenolic compounds. The effectiveness of Fe-deficiency resistance mechanisms described for hydroponically grown hawthorn have to be evaluated under soil conditions.