Boron: the essential element for vascular plants that never was

Area of Science:

• Plant Physiology
• Biochemistry
• Plant Nutrition

Background:

• Boron's essentiality for vascular plants has been accepted for nearly a century.
• This essentiality is based on criteria that may not fully apply to boron's role.
• An alternative interpretation suggests boron's function is indirect and related to mitigating toxicity.

Purpose of the Study:

• To challenge the established view of boron as an essential element for vascular plants.
• To propose an alternative hypothesis where boron is potentially toxic and requires detoxification.
• To explain the observed effects of boron deficiency and toxicity through this new framework.

Main Methods:

• Re-evaluation of existing scientific literature on boron's role in plants.
• Postulation of a detoxification mechanism involving boron's chemical binding.
• Identification of endogenous compounds, specifically phenolic metabolites, involved in boron detoxification.

Main Results:

• Boron's essentiality criteria are reinterpreted, suggesting its effects are indirect.
• Boron is proposed to be potentially toxic, with plants evolving mechanisms to manage this toxicity.
• Soluble phenolic metabolites, related to lignin biosynthesis, are implicated in binding and sequestering boron.
• This complexation alleviates the toxicity of both boron and the phenolic compounds.

Conclusions:

• Boron is not essential but potentially toxic to vascular plants.
• Plants utilize indirect chemical and physical sequestration mechanisms to manage boron toxicity.
• Observed "deficiency symptoms" are likely manifestations of phenylpropanoid toxicity, mitigated by boron.
• Boron's role is redefined as a detoxifying agent rather than an essential nutrient.