Allocation to floral structures in Thalictrum pubescens (Ranunculaceae), a cryptically dioecious species.

Area of Science:

• Plant reproductive biology
• Sexual dimorphism in plants
• Plant resource allocation

Background:

• Thalictrum pubescens exhibits sexual dimorphism, with females producing sterile pollen and males being unisexual.
• Understanding resource allocation in female plants producing non-functional structures is crucial for evolutionary studies.

Purpose of the Study:

• To investigate the resource investment in stamen production by female Thalictrum pubescens.
• To compare female stamen investment with that of male counterparts.

Main Methods:

• Comparative analysis of stamen biomass, nitrogen, and phosphorus content between sexes.
• Measurement of anther and filament size, and pollen quantity and size.
• Correlation analysis of pollen production with environmental conditions and flower morphology.

Main Results:

• Female stamens showed similar biomass and nutrient content but differed in filament length compared to males.
• Females produced more pollen per anther, with no difference in pollen size between sexes.
• A trade-off was observed in females between stamen number and pistil number, especially under low environmental variance.

Conclusions:

• Stamen production in female Thalictrum pubescens is not metabolically inconsequential.
• Resource allocation to stamens in females comes at the cost of pistil and seed production.
• This suggests a potential evolutionary constraint or strategy in plants with unisexual flowers.