A possible regulatory role for ethylene in the pollen-pistil interaction in a sporophytic self-incompatible system

Abstract

The sporophytic type of self-incompatibility exhibited by Ipomoea cairica Sweet (Convolvulaceae) was partially overcome in vitro by treating the pollen and/or stigma with 10 -'to 10 -'M methionine, a precursor of ethylene . The implications of these observations are discussed in relation to other experiments involving use of the ethylene antagonist AgNO 3 , individually and in combination with methionine and an optimum level of indole-3-acetic acid (10 -'M). The results suggest a role for ethylene (which could also be IAA-induced) in regulating pollen germination and further tube growth in sporophytic self-incompatible systems . A hypothesis on the action of hormones in pollen germination and tube growth in a sporophytic self-incompatible (SSI) system is presented .

The role of gibberellic acid in the pollen-pistil interaction in sporophytic self-incompatible systems

“…The auxin content of the style increased substantially after pollination [16,17], implying its de novo synthesis . These studies as well as our previous observations [7,24] have indicated a role for auxin in pollination and interaction of the two partners thereafter . The IAA-forming enzymes have been shown to increase following GA3 treatment [13,151 .…”

“…Most experimentation was done with Ipomoea cairica Sweet, due to the advantages it has over other taxa [7] . However, in order to obtain relevant information, some growth regulators known to partially remove the barrier to self-compatibility were also employed on two other taxa belonging to the Brassicaceae .…”

“…In general, the method of growing, maintaining, selecting and testing of plants as well as the specific methodology adopted for treating the interacting partners, were the same as described earlier [7,19,24,25] . Raphanus sativus Linn .…”

“…(1) treated stigma X untreated pollen, (2) treated stigma X treated pollen and (3) untreated stigma X treated pollen . For treating test material, 0 .5 ml of ethanol or water containing the required concentration of the compound to be tested was evaporated in a small vial, using a stream of air [7] . For controls, absolute ethanol was evaporated in a vial and the stigma and pollen were treated in such tubes .…”