Abstract
Elucidating the relationship between environmental factors and the flowering phenology of Melaleuca quinquenervia is crucial to understanding a key trait for this species’ invasive nature—its prolific flowering. This study investigates how temperature, soil moisture, water vapor concentration, and rainfall influence the timing and intensity of M. quinquenervia flower production in Southwest Florida. A 10-month observational study was conducted from June 2022 to March 2023 on five trees located in a small forest on the Florida Gulf Coast University’s campus. Environmental data was sourced from local weather stations and a soil moisture sensor, weekly inflorescence counts were recorded, and bud samples were collected from the five trees. This study reveals that M. quinquenervia’s flowering season began in July, two months earlier than previously reported for this species in South Florida and continued through December. Flower production was found to be closely linked to water availability, with a strong correlation between flowering and soil moisture levels three weeks prior and rainfall four weeks prior. Soil moisture was identified as the most significant environmental predictor for flowering, with trees producing more flowers during periods of high water availability, especially during the wet season (June–September).
The expression levels of three putative floral meristem identity genes in M. quinquenervia —LEAFY (MqLFY), FRUITFULL1 (MqFUL1), and FRUITFULL2 (MqFUL2)—were analyzed using Real Time quantitative PCR (RT-qPCR). MqFUL1 emerged as a reliable biomarker for flowering, with its expression significantly higher in flowering trees compared to non-flowering trees. Conversely, MqLFY and MqFUL2 were less consistent in predicting flowering. The expression of MqFUL1 and MqLFY was positively correlated with soil moisture levels, showing a lagged response of two weeks for gene expression rather than the three weeks observed for flower production. This suggests that MqFUL1 and MqLFY genes play a role in flowering in M. quinquenervia and are possible orthologs to LFY and AP1/FUL in Arabidopsis thaliana.