Effects of iron deficiency on photosynthetic structures in peach (Prunus persica L. Batsch) leaves

Abstract

Peach trees grown on calcareous soils (pH approximately 7.9), are usually affected by iron chlorosis. Most reports on the lack of chlorophyll induced by iron deficiency have been obtained with plants cultured in pots or hydroponic solution under controlled conditions. Under these conditions good correlations between total iron and chlorophyll concentration have been found, but in plants grown under field conditions inconsistent results have been generally obtained. Changes in the structure of thylakoids from iron-deficient higher plants grown under controlled conditions have been reported, but these have been not confirmed on plants grown in the field. In this work we have studied the infulence of lime-induced iron deficiency on some features of the thylakoids from iron deficient peach trees grown on calcareous soils. Leaves from iron-deficient peach trees (Prunus persica L. Batsch, vc Miraflores) were grouped into three different chlorophyll concentration levels (below 12, approximately 22 and 30 nmol cm^-2) and harvested. Changes in extractable iron, photosynthetic oxygen evolution, thylakoid polypeptide composition, chlorophyll protein complexes and photosynthetic pigments were investigated. The relative proportions of the different chlorophyll protein complexes were analyzed by non-denaturing SDS-PAGE. HPLC was used to analyze photosynthetic pigments. While the ratio between chlorophyll a/β-carotene did not change significantly, both the xanthophyll/chlorophyll b and chlorophyll a/chlorophyll b ratios were increased in samples with severe iron chlorosis. Thylakoid polypeptides were analysed by denaturing LiDS/Triton X-100-PAGE. Proteins affected by iron-chlorosis were found at 43 and 29 kDa (PS2) and cytochromes. All these results are discussed in relation to the structural changes in iron-deficient thylakoids of higher plants under field conditions.