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The article "Mechanical stimulation of the stigmas triggers switch from female to male phase in the protogynous trap flower of Aristolochia rotunda (Aristolochiaceae)" discusses the phenomenon of floral longevity and the plasticity of the female phase in dichogamous flowers. The study focuses on Aristolochia rotunda and investigates the hypothesis that the female phase is shortened after pollen deposition on the stigma. The researchers conducted experiments using hand pollination, presence of pollinators with or without pollen load, and mechanical stimulation of the stigmas. The results showed that the duration of the female phase depended on the presence of pollinators, regardless of whether they carried pollen, and that mechanical stimulation of the stigmas triggered the switch from female to male phase. The study suggests that this mechanical signal is adaptive when pollinators are limited, as it ensures the fulfillment of the flower's male function. [Extracted from the article]

Larger and longer lived flowers receive more pollinators, but may also involve increased water maintenance costs under hot, dry environments. Hence, smaller and/or short-lived flowers may buffer such costs. We surveyed floral longevity in three large-flowered MediterraneanCistusspecies. We hypothesize that: (1) inCistus, floral longevity decreases with increasing air temperature and flower size; (2) inC. ladanifer, flower size and longevity increase along an altitudinal gradient; (3) floral longevity is differentially affected by temperature rather than flower size along the gradient; (4) under similar temperature, floral longevity decreases with flower size. For each species, we evaluated the effects of flower size and air temperature on floral longevity. Specifically, floral longevity was surveyed along an altitudinal gradient in the largest flowered speciesCistusladanifer. Floral longevity inCistusspecies lasted < 1 d and was affected by air temperature, independently of flower size. InC. ladanifer, flower size increased along the gradient but floral longevity decreased. Still, floral longevity decreased with increasing air temperature and, to a lesser extent, with flower size. Together, our findings show a triangular relationship among air temperature, flower size and floral longevity with margins for plasticity to accommodate pollinator attraction with the costs of large-flowered Mediterranean plants. [ABSTRACT FROM AUTHOR]