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Studies were conducted to determine cellular site of Ca action in promoting pollen growth of Crinum asiaticum and a few other species. The following experimental results have strongly indicated that Ca binding takes place in pectins of the pollen tube walls. This appeared to increase the wall rigidity and to regulate permeability of the pollen cells thereby enhancing pollen growth. Radioactive Ca incorporation was observed exclusively in the pollen tube wall regions. The promoting action of Ca on pollen growth disappeared when pectinase was supplemented to the media. This was not the case with cellulase and other enzymes used. Methyl donors promoted pollen growth, and the promotion was more than doubled if Ca ions were present. Ethionine, on the other hand, inhibited tube elongation and exhibited no Ca effect. Growth of pollen tubes in oscillated liquid media during elongation was poorer than growth in standing media. The Ca effect was also reduced when pollen was oscillated. The observations made of the reduced rate of 45Ca incorporation when pollen was washed in water, and the hydroxylamineferric chloride test, have indicated that a considerable portion of these pectins are cold-water soluble. [ABSTRACT FROM AUTHOR]

Studies were conducted on the protective action of Ca against growth inhibition and death of pollen from Crinum asiaticum and Catharanthus roseus. Ca ions not only promoted pollen germination and pollen tube growth, but also were antagonistic to pollen injuries induced by various chemical and physical treatments. Most of the chemicals used seemed to act as osmotic inhibitors. Among the chemical agents tested, DNP inhibited pollen germination more strikingly with Ca than without it, whereas pollen tube growth was enhanced. Another metabolic inhibitor, low temperature, showed a similar effect on pollen germination. Insignificant or no protective action of Ca was observed when IAA, TIBA and coumarin, were applied. Large populations of pollen when grown in cultural media without Ca showed a partial protective action. The protective action of Ca in pollen growth against various inhibitors required other cations such as Mg and K ions. The promoting of pollen growth by Ca also required these other cations. The protective action of Ca is considered to be based on its binding in the pollen cell walls, particularly in the pectic regions. This gives rise to a decreased permeability and increased structural rigidity against the chemical and physical inhibitors. [ABSTRACT FROM AUTHOR]

Physiological studies of self incompatibility were made with Oenothera organensis. Techniques used included a relatively simplified method of semi-vitro or stylar culture of pollen. The presence of Ca ions at certain levels in either cultural medium or pre-soaked stylar sections partially overcame the incompatibility reaction. The Ca action is believed to be due to either protection of pollen cell walls from the incompatibility inhibition or increased cell wall rigidity which leads to the promotion of pollen tube growth. Therefore, the probable site of the incompatibility reaction is considered to be at the surface of the pollen tube wall. Better pollen growth was observed when a larger pollen population was introduced to the stigma. This is regarded as an increase in the quantity of available Ca for pollen growth. Either addition of Ca to the cultural media or the stylar sections for small populations of pollen resulted in considerable promotion of tube growth the incompatibility reaction was also partially overcome by either a cold temperature (5°C) during, or high temperature (50°C) prior to the growth period. It is assumed that the temperature effect is probably due to the inactivation of a certain protein, possibly enzymatic in nature, involved in the incompatibility reaction. [ABSTRACT FROM AUTHOR]