Flavonoids, Alkali Earth, and Rare Earth Elements Affect Pecan Pollen Germination

Abstract

<jats:p>The factors regulating pecan [<jats:italic>Carya illinoinensis</jats:italic> (Wangenh.) K. Koch] pollen grain germination are poorly understood for both in vitro pollen viability tests and on receptive stigmatic surfaces of pistillate flowers. Potential regulating factors include flavonols, calcium (Ca), Ca-like alkali earth elements (AEEs), and rare earth elements (REEs). When various concentrations of certain naturally occurring simple flavonols (e.g., quercetin, kaempferol, myricetin, naringenin, and hesperetin) were tested in vitro by adding to standard pecan pollen germination medium, hesperetin, myricetin, and kaempferol functioned as a strong agonist at low concentration (0.12–2.0 µ<jats:sc>m</jats:sc> for hesperetin and kaempferol, and 0.25 µ<jats:sc>m</jats:sc> for myricetin), increasing pollen germination 2- to 3.9-fold over flavonol-free media. Hesperetin and myricetin were antagonistic at 16 µ<jats:sc>m</jats:sc>. Kaempferol was not antagonistic at any concentration up to and including 16 µ<jats:sc>m</jats:sc>. Naringenin was an antagonist at concentrations from 0.12 to 16 µ<jats:sc>m</jats:sc>; whereas, quercetin was an antagonist at 8–16 µ<jats:sc>m</jats:sc>, but tended to function as an agonist at low concentration (0.12–0.50 µ<jats:sc>m</jats:sc>). The equal molar replacement of Ca<jats:sup>2+</jats:sup> in standard pecan pollen germination media by single REEs, resulted in certain REEs [e.g., yttrium (Y), gadolinium (Gd), and thulium (Tm)] partially replacing the obligate need for Ca<jats:sup>2+</jats:sup>; thus, functioning as agonists in absence of Ca. All non-Ca AEEs [beryllium (Be), magnesium (Mg), strontium (Sr), expect for barium (Ba)], also partially substituted for Ca<jats:sup>2+</jats:sup> at equivalent molar concentrations, but none were as efficacious as Ca<jats:sup>2+</jats:sup>. Results are suggestive that a) pollen germination in in vitro test can be improved by incorporation of certain flavonols, and b) pollen germination on stigmatic surfaces of flowers in orchards might be influenced or regulated by flavonol composition and Ca-like metals in the liquid matrix of the wet (receptive) stigmatic surface.</jats:p>

Micromorphological and histochemical attributes of flowers and floral reward in Linaria vulgaris (Plantaginaceae)

“…Several studies have demonstrated that pollen grains of different plant species are a rich source of flavonoids, which are known to be involved in pollen fertility and they are detected exclusively in tapetum cells (Taylor and Grotewold 2005 ). Pollen derivative flavonoids may also accelerate the pollen tube formation and its germination on the stigma (Wood 2017 ). Moreover, flavonoids protect the pollen grains from the harmful effects of solar radiation (Flenley 2011 ) and guard against other abiotic and biotic stress factors (Winkel-Shirley 2002 ; Pourcel et al 2007 ).…”

Secretory Structures of Pogostemon auricularius: Morphology, Development, and Histochemistry

“…As assumed in previous studies, the bulk of the essential oils were found in the peltate trichomes of Lamiaceae [21,22], the secretory material that was produced by peltate trichomes of P. auricularius contained lipids. In plants, the flavones may function as sunscreen pigments and/or antioxidants to alleviate adverse effects that are caused by UV light or oxidative damage, and to regulate auxin transport [23,24].…”

Glandular trichomes of Robinia viscosa Vent. var. hartwigii (Koehne) Ashe (Faboideae, Fabaceae)—morphology, histochemistry and ultrastructure

“…They protect plants against bacterial or viral attack by counteracting excessive production of reactive oxygen species (Khalid et al 2019) and via their antifungal and antifeedant activities (Bergau et al 2015;Kundan et al 2019). An additional function of flavonoids is to protect plants against UV-B radiation (Tang et al 2020) and regulate auxin transport (Wood 2017). The presence of robinin, i.e.…”