Relationship between polar basipetal auxin transport and acropetal Ca2+ transport into tomato fruits

Abstract

The dependence of acropetal Ca2+ transport on polar basipetal indoleacetic acid (IAA) transport was investigated in excised tomato fruits (Lycopersicon esculentum L. Mill.) using an in vitro fruit system. Auxin transport inhibitors like triiodobenzoic acid (TIBA), chlorofluorenolmethyl ester (CME) and naphthylphthalamic acid (NPA) were used in order to investigate the effect of restricted polar basipetal auxin transport on the acropetal transport of 45Ca2+, 86Rb+ and 98Sr2+ into the same fruits. TIBA and CME inhibited basipetal transport of IAA. particularly in 10‐ to 12‐day‐old tomato fruits, and simultaneously restricted the acropetal transport of 45Ca2+. The auxin transport inhibitors failed to significantly reduce the upward transport of 86Rb+ and the transport of 96Sr2+ was less inhibited than that of 45Ca2+. TIBA and CME did not significantly affect the acropetal transport of labelled water into the fruit, nor the cation‐exchange capacity or K+ and Mg2+ concentrations in the tomato fruit. These results support the view that a part of the Ca2+‐specific acropetal transport into tomato fruits is associated with the polar basipetal IAA transport. This Ca2+ transport is independent of the transpiration stream into the fruit and the cation exchange capacity of the fruit tissue.