Evidence of different compounds in smoke derived from legumes and grasses acting on seed germination and seedling emergence

Abstract

Our previous study showed that smoke derived from alfalfa (Medicago sativa) caused different germination responses compared with that from prairie hay (Festuca hallii) and wheat straw (Triticum aestivum), but the mechanism remained unclear. In this study, we used Salad Bowl lettuce (Lactuca sativa) as a quick bioassay to trace the active compounds in each of these three smoke solutions. Column chromatography and high performance liquid chromatography (HPLC) were used to separate and identify active fractions. Seeds of four species from Fescue Prairie were primed for 24 h at room temperature in darkness using serial dilutions of separated active fractions, as well as karrikinolide (KAR1). After priming, seeds were dried at room temperature in darkness for 7 days and subsequently incubated at 10/0°C or 25/15°C in 12 h light–12 h dark or 24 h darkness for 49 days. KAR1was in the smoke made from prairie hay, and wheat straw, but was absent in alfalfa smoke. Priming in KAR1solutions increased germination of three native species. Priming in highly concentrated KAR1reduced radicle length ofCirsium arvense, the only non-native species. Even though KAR1has the potential to enhance regeneration of native species in the Fescue Prairie, KAR1is not universally present in smoke derived from different plant materials. Unknown compound(s) in smoke derived from legumes remain to be identified.

Smoke-Water Enhances Germination and Seedling Growth of Four Horticultural Crops

“…The current study clearly shows that plant-derived smoke-water treatments, particularly the smoke-water derived from white willow (SW 1 ) and lemon eucalyptus (SW 5 ), effectively improved GP, GR, and seedling growth of the tested crops. In accordance with our results, previous studies have shown that smoke-water and smoke-derived compounds have a positive effect on seed germination and the post-germination parameters of crops such as wheat [47], onion [48], tomato [49], okra [50], papaya [51], and lettuce [14,27]. Additionally, our results provide evidence that smoke-water can actively break dormancy in gladiolus [52].…”

“…Indeed, there is scientific debate about the effects of smoke-water and its active compounds (KARs) on germination parameters and whether smoke-water can substitute for light conditions or not. The germination percentage of some light sensitive crops such as lettuce seeds ( Lactuca sativa ) can be significantly increased under dark conditions by using smoke-water [6,27]. On the other hand, Nelson et al [28] showed that the effect of KAR on Arabidopsis seed germination was observed only under light conditions and not under dark conditions, which confirms the results found in tomato, gladiolus, and scotch marigold in the current study.…”

“…A comparison of our findings with those of other studies confirms that smoke-water has distinct biological functions with regard to seed germination. Nevertheless, its influence may be affected by the presence/absence of light and the plant species [6,27,54].…”

“…Interestingly, few studies have found evidence that seed dormancy and germination response to smoke are affected by light. Ren et al [27] reported that germination of lettuce seeds was better promoted under dark conditions by using smoke-water. However, Nelson et al [28] reported that the Arabidopsis seed germination was observed only under light conditions and not under dark conditions in response to KAR treatment.…”

“…Although some previous studies have shown that the smoke-water can be prepared from all plant species, and that their effect is similar on seed germination [30,31], Smith et al [32] reported that there may be thousands of unknown compounds in smoke, and that the positive effects of smoke on seed germination may depend on the plant species. Additionally, a recent study has reported that the active compounds that can stimulate seed germination have not existed in smoke derived from different legume materials [27]. Also, smoke produced from alfalfa affects seed germination differently compared with that produced from wheat straw and prairie hay [33], indicating that quantitative and qualitative variations exist in smoke solutions derived from different materials.…”