ABSTRACT:

In Arum, bigger individuals should proportionally invest more in the female function (number or weight of female flowers) than the male. The aim of this paper is to quantify variations in reproductive characters (size of the spadix parts, number of inflorescences) in relation to plant and inflorescence sizes. The appendix represents 44% of the spadix length. The female zone length represents 16.5% of the spadix length and is much longer than the male zone (6%). Moreover these three spadix zones increase with plant vigour indicating an increasing investment into reproduction and pollinator attraction. It appears that the length of appendix increased proportionally more than the lengths of the fertile zones. On average an inflorescence counts 156 male flowers and 61 female flowers which result in a male-biased floral ratio in A. italicum. The numbers of male and female flowers increased significantly with the spadix size but differently according to the gender, the number of female flowers increasing faster than male: on the other hand this effect was marginally significantly (p = .08). This relative gender difference of flower number increase is visualised by a significant decrease of the maleness floral ratio with spadix size.