Allelopathic effects of glucosinolate breakdown products in Hanza [Boscia senegalensis (Pers.) Lam.] processing waste water

Abstract

Boscia senegalensis is a drought resistant shrub whose seeds are used in West Africa as food. However, the seeds, or hanza, taste bitter which can be cured by soaking them in water for 4–7 days. The waste water resulting from the processing takes up the bitter taste, which makes it unsuitable for consumption. When used for irrigation, allelopathic effects were observed. Glucosinolates and their breakdown products are the potential causes for both the bitter taste and the allelopathic effects. The objectives of this study are to identify and quantify the glucosinolates present in processed and unprocessed hanza as well as different organs of B. senegalensis, to analyze the chemical composition of the processing water, and to pinpoint the causal agent for the allelopathic properties of the waste water. Hanza (seeds without testa), leaves, branches, unripe, and ripe fruits were collected in three populations and subjected to glucosinolate analyses. Methylglucosinolates (MeGSL) were identified in all plant parts and populations, with the highest concentrations being found in the hanza. The levels of MeGSLs in the hanza reduced significantly during the soaking process. Waste water was collected for 6 days and contained large amounts of macro- and micronutrients, MeGSL as well as methylisothiocyanate (MeITC), resulting from the conversion of glucosinolates. Waste water from days 1–3 (High) and 4–6 (Low) was pooled and used to water seeds from 11 different crops to weeds. The High treatment significantly delayed or reduced germination of all the plant species tested. Using similar levels of MeITC as detected in the waste water, we found that germination of a subset of the plant species was inhibited equally to the waste water treatments. This confirmed that the levels of methylisiothiocyanate in the waste water were sufficient to cause the allelopathic effect. This leads to the possibility of using hanza waste water in weed control programs.

Stress-Related Mitogen-Activated Protein Kinases Stimulate the Accumulation of Small Molecules and Proteins in Arabidopsis thaliana Root Exudates

“…As this transgenic system is known to strongly stimulate indolic GLS production (Lassowskat et al, 2014 ), one possibility is that these are rapidly metabolized once secreted into the root apoplast. GLSs and their derivatives have long been associated with plant resistance to insects or pathogens (Sotelo et al, 2015 ) or also in allelopathic plant-plant communications (Rivera-Vega et al, 2015 ). For the latter, direct treatment with GLS-containing brassica meal or extracts regulate growth of surrounding plants (Brown and Morra, 1996 ) and brassica plants have been used for crop rotation or intercropping as weed control in agricultural practices (Haramoto and Gallandt, 2004 ).…”

Glucosinolate-Derived Isothiocyanates Inhibit Arabidopsis Growth and the Potency Depends on Their Side Chain Structure

“…Glucosinolate-containing plants have also been used in biofumigation to control soil pests and weeds [ 11 ], and several ITCs have been shown to inhibit seed germination [ 12 , 13 ]. Applying ITCs directly onto plant leaves leads to phytotoxic effects such as chlorosis, cell death and reduced growth, and can ultimately lead to plant death [ 14 , 15 , 16 , 17 ]. At the plant cellular level ITCs have so far been shown to trigger the closure of stomata, to lead to the production of reactive oxygen species (ROS), to lead to glutathione depletion, to affect the cell cycle, to disintegrate microtubules, to inhibit actin-mediated intracellular transport, and to lead to important changes in gene expression profiles in Arabidopsis thaliana [ 17 , 18 , 19 , 20 , 21 , 22 , 23 ].…”

Allelopathic effects of native and invasive Brassica nigra do not support the novel‐weapons hypothesis

“…Given their known role in allelopathic interactions (Turk and Tawaha, 2003; Rivera‐Vega et al, 2015), glucosinolates could underlie the allelopathic effects of B. nigra extracts. The most abundant glucosinolate in B. nigra is sinigrin, and invasive B. nigra had higher levels of sinigrin than native B. nigra when grown in the field (Oduor et al, 2011).…”