Summary The epidermal hair and stomata are two types of specialized structures on the surface of plant leaves. On mature maize leaves, stomatal complexes and three types of hairs are distributed in a stereotyped pattern on the adaxial epidermis. However, the spatiotemporal relationship between epidermal hair and stomata development and the regulatory mechanisms governing their formation in maize remain largely unknown. Here, we report that three homologous ZmSPL transcription factors, ZmSPL10, ZmSPL14 and ZmSPL26, act in concert to promote epidermal hair fate on maize leaf. Cytological analyses revealed that Zmspl10/14/26 triple mutants are completely glabrous, but possess ectopic stomatal files. Strikingly, the precursor cells for prickle and bicellular hairs are transdifferentiated into ectopic stomatal complexes in the Zmspl10/14/26 mutants. Molecular analyses demonstrated that ZmSPL10/14/26 bind directly to the promoter of a WUSCHEL‐related homeobox gene, ZmWOX3A, and upregulate its expression in the hair precursor cells. Moreover, several auxin‐related genes are downregulated in the Zmspl10/14/26 triple mutants. Our results suggest that ZmSPL10/14/26 play a key role in promoting epidermal hair fate on maize leaves, possibly through regulating ZmWOX3A and auxin‐related gene expression, and that the fates of epidermal hairs and stomata are switchable.

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Phenolic acids are the main active substances that contribute to the antioxidant activity of Echinacea purpurea (L.) Moench, Asteraceae. However, the effect of chromosome doubling and developmental growth stage on the phenolic acid accumulation and the antioxidant capabilities of E. purpurea has remained unclear. Our systematic studies indicate that the dry weight of tetraploid plants is significantly higher than that of diploid plants, leading to higher yields of cichoric acid, caffeic acid, chlorogenic acid, caftaric acid, and 1,5-dicaffeoyl quinic acid compared with diploid plants, at different growth stages. Cichoric acid and caftaric acid are the predominant compounds in diploid individuals. The period with the higher yields of cichoric acid and caftaric acid are coincided with that of total phenolic acids in four investigated organs (root, leaf, stem, and flower), which mostly observed during the flowering period (August). Furthermore, antioxidant activities in four different organs of tetraploid individuals were higher than those in diploid plants, at each growth stage. The changes in the antioxidant activity in different organs (flower, root, leaf, and stem) of diploid individuals were significantly and positively correlated with the trends in the content changes of total phenolic acids throughout different growth stages. Blooming time should be chosen as the best harvest time for both diploid and tetraploid plants, and the flowers and leaves may be used as raw materials for the extraction of total phenolic acids and development of antioxidant supplements to stimulate the immune system.

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