The biological effects and mode of action of a chemical hybridising agent
The behaviour of the chemical hybridising agent, WL84811, was studied on diverse plant systems. Information about its effect on germinating seeds and on growth of the unicellular alga Chlorella was used to complement information obtained from direct studies on pollen. Although work with germinating seeds showed that WL8481J affects coleoptile and root growth somewhat differently, there were similarities between the responses of the seed and algal systems. In both cases, WL84811 has two separate effects: at low WL84811 concentrations, much higher concentrations of proline (the amino acid implicated in determining pollen viability, of which WL84811 is an analogue) cannot overcome its effect significantly; however, at high WL84811 concentrations the same concentration of proline significantly reduces the effect of WL84811. WL84811 causes the production of giant algal cells which fail to divide normally until the cells are returned to medium without WL84811. Azetidine-2-carboxylic acid (A2C), the naturally-occurring isomer of WL84811 also inhibits growth in both systems but proline is unable to ameliorate its effect at any concentration. In vivo pollination experiments showed that the gametocidal effect of WL84811 is expressed solely through the pollen, which is prevented from germinating. The development of wheat pollen is severely affected by stem-injection with WL84811 and is unable to germinate in vitro. No such effect is apparent with rye pollen. Addition of WL8481J to the germination medium has little effect on pollen germination of either the bi- or trinucleate pollen tested. In some cases pollen tube length is reduced by WL84S11 and in other cases it is increased; some pollen may utilise the compound as a nitrogen source after germinating. WL84811 does not appear to act in the same way as its isomer A2C, at least at higher concentrations. It may be involved in some aspect of wall formation common to the division of algae, root and coleoptile extension and pollen tube growth.