When sunlight goes out, avoidance mechanisms are defective for protecting flowers from freezing damage

In high mountain species, flowers are considered the most frost-sensitive organs of plants. Such frost sensibility relates to the fact that most flowers do not tolerate ice formation in their tissues, suggesting that freezing avoidance mechanisms would be highly selected to protecting these vital organs from freezing damage. Despite this, the function and regulation of avoidance mechanisms in flowers have been poorly studied. This study assessed the importance of freezing avoidance mechanisms in alpine species from the central Chilean Andes. Reproductive shoots of 14 herbaceous species from the subalpine and low alpine belts in the central Chilean Andes were collected during peak flowering in the field and transported to the lab to study ice formation and propagation. The frequency and effectiveness of structural ice barriers (SIB) and the effect of inflorescence morphology on thermal decoupling were quantified by infrared thermography. SIBs were detected in 9 out of the 14 studied species but were effective only in three. Moreover, no thermal decoupling was detected in any studied species, independent of their inflorescence type. We conclude that SIBs and inflorescence morphology are insufficient to protect flowers from damage caused by night freezing events.