Wax Extracted from Waste Cauliflower Leaves Shows Potential Antitranspirant Efficacy When Applied to Rapeseed Plants

Abstract

The stress from excessive transpiration of water from plant leaves can damage crop growth during droughts. Specific commercial biostimulant products (antitranspirants) are available to reduce transpiration when applied to plants, but these products are expensive. Antitranspirants from waste would be cheaper, and the aim of this research was to extract leaf wax from a fresh produce processing waste and conduct a preliminary evaluation of its antitranspirant efficacy. Supercritical CO2 was used to extract wax from cauliflower leaves, and after formulating for spraying, the wax was applied to young rapeseed plants in three consecutive experiments. The wax was compared with a commercially-available terpene antitranspirant (di-1-p-menthene) for efficacy in reducing stomatal conductance and water use. In two of the three experiments, stomatal conductance was significantly reduced to similar extents by wax and by di-1-p-menthene, despite the wax being formulated and applied at a much lower concentration. Water use was reduced by wax in one experiment. Further research is needed on formulation, spraying conditions, and dose-response. These preliminary results demonstrate the potential for extracted leaf wax to act as a biostimulant and ameliorate plant drought stress.

Commercial uses of antitranspirants in crop production: A review

“…Granger and Trager, 2002) has been done on them. Faralli et al (2022) who evaluated wax extracted from cauliflower waste on rapeseed found the product as effective as di-1-p-menthene in reducing stomatal conductance and improving water use efficiency. In bedding plants, a low concentration (10 mM) of food-grade vinegar (acetic acid) improved plant survival following 3–4 weeks of drought (Allen and Allen, 2021).…”

“…Therefore, relatively speaking, for arable crop production, the current commercial ATs are expensive, as Faralli et al (2022) noted. Another reason for the neglect of ATs in crop production could be the erroneous conclusion of AT research in the 1970s that discouraged the use of ATs in crop production.…”

Restricting growth for improved fresh produce scheduling: A role for stomatal blockers?

“…For example, one of the common commercial products, di‐1‐ p ‐menthene, is derived from pine resin 8 . Other polymers which can act as stomatal blockers and are possibly even more‐acceptable to consumers are natural products derived from plant extracts without chemical modification and may include extracted leaf wax, 16 and vegetable oil 17 . An additional advantage of vegetable oils is their much lower cost, and as a consequence they may be more likely to be adopted by smallholder farmers in low‐income countries.…”