Reproductive biology of the perennial desert shrub, Thymelaea hirsuta: Studies in gender, self-fertility and architecture.

摘要

Thymelaea hirsuta (Thymelaeaceae) is a xerophytic evergreen shrub common to the Mediterranean region and known to demonstrate significant variability in sex expression. A series of observational and experimental studies were carried out to investigate the nature of this variability in greenhouse-raised plants. Following seedling establishment, an irrigation treatment was applied. Plants were watered every 3 days, 6 days or 9 days. A survey of two year old flowering plants (n = 305) showed significant bimodality in sex expression. Quantitative gender estimates indicated that individual plants tended to be either more male or more female. Water treatment had no significant effect upon estimates of gender, number of male flowers, number of female flowers, total number of flowers or an index of sexual lability. A controlled pollination study revealed significant differences in seed mass among geitonogamous, half-sib and outcrossed treatments, resulting in an estimate of inbreeding depression ($delta$) of 0.23. Nonsignificant differences in fruit set were also observed. To examine the effect of water treatment on various morphological (u22architecturalu22) parameters, repeated measurements were taken every two months on a subset of 202 plants for a total of ten months. Water treatment, time and the interaction effect between water treatment and time all significantly affected plant architecture, particularly height. Male, female and hermaphrodite flowers were compared for differences in position. There were significant differences among male, female and hermaphrodite flowers with respect to plant height, vertical distribution and branch order, suggesting that male flowers and female flowers may have different morphological optima. (Abstract shortened by UMI.)Dept. of Biological Sciences. Paper copy at Leddy Library: Theses u26 Major Papers - Basement, West Bldg. / Call Number: Thesis1996 .M65. Source: Masters Abstracts International, Volume: 37-01, page: 0182. Adviser: Jon Lovett Doust. Thesis (M.Sc.)--University of Windsor (Canada), 1996.