Hormonome Dynamics During Microgametogenesis in Different Nicotiana Species

Plant microgametogenesis involves stages leading to the progressive development of unicellular microspores into mature pollen. Despite the active and continuing interest in the study of male reproductive development, little is still known about the hormonomics at each ontogenetic stage. In this work, we characterized the profiles and dynamics of phytohormones during the process of microgametogenesis in four Nicotiana species (Nicotiana tabacum, Nicotiana alata, Nicotiana langsdorffii, and Nicotiana mutabilis). Taking advantage of advanced HPLC-ESI-MS/MS, twenty to thirty endogenous hormone derivatives were identified throughout pollen ontogenesis, including cytokinins, auxins, ABA and its derivatives, jasmonates, and phenolic compounds. The spectra of endogenous phytohormones changed dynamically during tobacco pollen ontogeny, indicating their important role in pollen growth and development. The different dynamics in the accumulation of endogenous phytohormones during pollen ontogenesis between N. tabacum (section Nicotiana) and the other three species (section Alatae) reflects their different phylogenetic positions and origin within the genus Nicotiana. We demonstrated the involvement of certain phytohormone forms, such as cis-zeatin- and methylthiol-type CKs, some derivatives of abscisic acid, phenylacetic and benzoic acids, in pollen development for the first time here. Our results suggest that unequal levels of endogenous hormones and the presence of specific derivatives may be characteristic for pollen development in different phylogenetic plant groups. These results represent the currently most comprehensive study of plant hormones during the process of pollen development.

The role of quercetin in plants

Flavonoids are a special category of hydroxylated phenolic compounds having an aromatic ring structure. Quercetin is a special subclass of flavonoid. It is a bioactive natural compound built upon the flavon structure nC6(ring A)-C3(ring C)-C6(ring B). Quercetin facilitates several plant physiological processes, such as seed germination, pollen growth, antioxidant machinery, and photosynthesis, as well as induces proper plant growth and development. Quercetin is a powerful antioxidant, so it potently provides plant tolerance against several biotic and abiotic stresses. This review highlights quercetin’s role in increasing several physiological and biochemical processes in under stress and non-stress environments. Additionally, this review briefly assesses quercetin’s role in mitigating biotic and abiotic stresses (e.g., salt, heavy metal, and UV stress). The biosynthesis of flavonoids, their signaling pathways, and quercetin’s role in plant signaling are also discussed.

Effect of freezing conservation time on loquat (Eriobotrya japonica) pollen germination

Aim of study: Several studies point out that storage at -20 ºC is a suitable method for preserving pollen of many species in the long term. Part of those studies indicate the total storage time at which these conditions are optimal. However, we have found a lack of information about the freezing time conditions and incubation temperature of loquat pollen. The main objective of this study was to evaluate the effect of the -20 ºC conservation temperature on loquat (Eriobotrya japonica (Thunb.) Lindl.) pollen.Area of study: The study was conducted in Montserrat (Valencia, Spain).Material and methods: Loquat flowers were collected in November 2017 and stored at -20 ºC for three time periods: 4 (T1), 6 (T2) and 8 (T3) months. Subsequently, pollen grains were incubated at different temperatures for 72 h. We analyzed (i) the effect of freezing conservation time; (ii) the effect of incubation temperature on germination; (iii) the interaction between these two factors.Main results: T1 showed higher germination percentage and tube length values (mean and maximum) than T2 and T3. The highest germination percentage (52.77%) was detected for T1 at an incubation temperature of 25 ºC. The interaction between freezing time and incubation temperature showed more consistent results for T1 than for T2 and T3.Research highlights: This suggests that storing at -20 ºC for more than 4 months affects pollen grain and reduces germination and pollen growth. Therefore, -20 ºC loquat pollen storage should not exceed 4 months.