Why can Mikania micrantha cover trees quickly during invasion?

Area of Science:

• Ecology
• Plant Biology
• Invasive Species Research

Background:

• Mikania micrantha poses a significant threat to forest biodiversity by rapidly climbing and covering native trees.
• Understanding the physiological mechanisms behind M. micrantha's aggressive growth is crucial for developing control strategies.

Purpose of the Study:

• To investigate the growth response of M. micrantha when climbing and losing support.
• To elucidate the role of plant hormones, soluble sugars, and trehalose-6-phosphate (T6P) in M. micrantha's branching and canopy-covering abilities.

Main Methods:

• Simulated M. micrantha climbing by planting seedlings with local tree species (Cryptocarya concinna).
• Induced turning growth in M. micrantha stems to mimic post-support loss conditions.
• Analyzed plant hormone, soluble sugar, and T6P content in different stem parts.
• Utilized transcriptome data to understand gene expression under erect vs. turning conditions.

Main Results:

• M. micrantha stems exhibited turning and creeping growth after losing support at the tree canopy.
• Significant accumulation of auxin, cytokinin, gibberellin, soluble sugars (sucrose, glucose, fructose), and T6P occurred at the turning part (TP) of the stem.
• Transcriptome analysis revealed molecular pathways potentially regulated by sugars and hormones.

Conclusions:

• Lack of support triggers turning growth, leading to enhanced sugar and T6P levels at the TP.
• These changes likely promote dormant bud release and sustained branch elongation, enabling rapid canopy coverage.
• A hypothetical model suggests sugar and hormone regulation is key to M. micrantha's invasive success.