Bioactive compounds in extracts from short rotation willow shoots known as pharmaceuticals and experimental demonstration of biostimulation of maize plants by these chemical complexes

Abstract

Extracts from willow bark or leaves were shown to contain effective plant biostimulants and pharmaceutical compounds. Considering the limitation in the use of bark raw materials on large scale, here we analyzed the stimulatory effects of extracts from various organs of willow (Salix viminalis L) plants grown as short rotation shrub willow. Metabolomic analysis of water extracts from different organs (leaves, meristems, stems) of two triploid genotypes (Rába and Maros) revealed presence of bioactive compounds. Quantity of phenylpropanoids, flavones, flavonols, anthocyanins, aminobenzoate degradants, plant hormones and stylbenes varied between organs and genotypes. Several of these bioactive compounds are known as pharmaceuticals. Here we carried out phytostimulatory tests by using various extracts for seed priming and foliar spraying of maize plants in greenhouse and field experiments. Both the digital imagining of maize plants and measurements of the plant height showed variable stimulation of growth. Chlorophyll fluorescence parameters indicated improved photosynthetic performance. Increased seed weight/ear and 1000 seed weight (17%) were detected after foliar spraying. The present study supports the extended application of bioactive phytocompounds by offering a novel raw material, the short rotation willow shoots as sources of bioactive compounds for use in agricultural practice and pharmaceutical industry.

Keywords: LC-MS/MS; Salix sp.; active phytobiological metabolites; metabolomic pathways; seed priming; spraying.

Figure 1

Effects of priming hybrid maize seeds with water extracts from willow plants on shoot surface area. (A) growth curve of maize plants primed with Maros extracts (total green pixels); (B) growth curve of maize plants primed with Rába extracts (total green pixels); All the parameters were quantified by digital imaging. ML, Maros leaf; MM, Maros meristem; MS, Maros stem; RL, Rába leaf; RM, Rába meristem; RS, Rába stem. Statistically significant events are denoted as p ≤ 0.05 *, N=5 plants.

Figure 2

Differential response of plant height (A) and stem diameter (B) of maize plants to seed priming and foliar spraying with willow extracts. ML, Maros leaf; MM, Maros meristem; MS, Maros stem; RL, Rába leaf; RM, Rába meristem; RS, Rába stem. Statistically significant events are denoted as p ≤ 0.001 ***, p ≤ 0.01 **, and p ≤ 0.05 *, N=5 plants.

Figure 3

Growth curves of the root systems of hybrid maize plants treated with various willow extracts. (A) Seed priming with Maros extracts, (B) Foliar spray using Maros extracts, (C) Seed priming with Rába extracts, (D) Foliar spray using Rába extracts. ML, Maros leaf; MM, Maros meristem; MS, Maros stem; RL, Rába leaf; RM, Rába meristem; RS, Rába stem. Statistically significant events are denoted as p ≤ 0.01 **, and p ≤ 0.05 *, N=5 plants.

Figure 4

Stem extracts from two short rotation willow genotypes stimulate the development of root systems of maize hybrid plants following seed priming and foliar spray. MM, Maros meristem; MS, Maros stem; RM, Rába meristem; RS, Rába stem. Digital images were captured at the end of the growing period.

Figure 5

Kinetic representation of the OJIP transients from hybrid maize leaves that were treated with water or willow extracts derived from meristem and stem tissues. The kinetic curves of OJIP can indicate alterations in the primary photochemical reaction and the photosynthetic function of PSII. N=5 plants.

Figure 6

Height (cm) of maize hybrid plants at the seven-leaf stage as markers of growth characteristics in response to seed priming using various willow extracts. (A) measurements in the Szeged location; (B) measurements in the Mórahalom location. ML, Maros leaf; MM, Maros meristem; MS, Maros stem; RL, Rába leaf; RM, Rába meristem; RS, Rába stem. Statistically significant events are denoted as p ≤ 0.001 ***, p ≤ 0.01 **, and p ≤ 0.05 *, N=60 plants.

Figure 7

10-days growth of the hybrid maize plants following foliar spray with different willow extracts. (A) measurements in the Szeged location; (B) measurements in the Mórahalom location. ML, Maros leaf; MM, Maros meristem; MS, Maros stem; RL, Rába leaf; RM, Rába meristem; RS, Rába stem. Statistically significant events are denoted as, p ≤ 0.01 **, and p ≤ 0.05 *, N=60 plants.