Effect of Planting Time and Corms Treatment with Gibberellic Acid on Growth, Flowering, and Vase Life of Freesia hybrida ‘Corona’

Freesia hybrida is one of the most important cut flowers with a short vase life. The present study was conducted to explain the effect of the two planting dates December 1st and 15th and soaking corms before planting in gibberellic acid at concentrations of 0, 75, and 150 mg·L−1 on the growth, flowering, and flowers quality of Freesia hybrida ‘Corona’. A larger diameter of the inflorescence stem and floret head, fresh weight of inflorescence, and longer vase life were obtained when planted on December 1st. Soaking the corms in a GA3 solution of 150 mg·L−1 before planting significantly extended the vase life compared to the control. Finally, it can be concluded that the planting of corms soaked in a solution of 150 mg·L−1 GA3 on December 1st in unheated greenhouses can improve the growth, development, and quality of flowers of Freesia hybrida ‘Corona’.

Effect of biological and chemical treatments during flowering on stem-end rot, and mango yield

Pathogenic fungi, as Botryosphaeriaceae family, can penetrate during flowering and endophytically colonize the stem of mango fruit (Mangifera indica) without causing any visible symptoms. Those fungi become active during abiotic stress or fruit ripening and cause stem and inflorescence dieback or fruit stem-end rot (SER). We hypothesized that antifungal treatments during the main event of Botryosphaeriaceae penetration would reduce the disease. Initially, we showed that treatments with Switch [fludioxonil and cyprodinil] during orchard flowering (cv. Keitt and Shelly) reduced the occurrence of pathogenic fungi in the fruit stem end and significantly reduced fruit's SER. As mango orchards are sprayed weekly against powdery mildew during flowering, we combined two treatments against powdery mildew with two treatments against both powdery mildew and SER-causing pathogens. Application of biological treatments of Serenade [Bacillus subtilis] or chemical treatments of Luna Tranquility [fluopyram and pyrimethanil] or Switch during flowering in 'Shelly' and 'Keitt' mango orchards significantly reduced inflorescence/stem dieback (up to 50%) and fruit drop and significantly increased the number of fruit per tree, which led to a significant increase in yield, up to 41%, in heavily infected orchards. In addition, this application during flowering (March–April) affected postharvest fruit quality (August–September) by a significant (p<0.005) reduction of incidence and severity of stem-end rots and even fruit side rot, without affecting fruit ripening and other quality parameters. While all fungicides were effective, the chemical fungicides were more effective than the biological fungicide. Thus, changing the powdery mildew fungicide regime to control also the Botryosphaeriaceae penetration during mango orchard flowering, led to reduced inflorescence/stem dieback, reduced fruit drop, increase in yield, and minimize postharvest decay.

Histone methyltransferase ATX1 dynamically regulates fiber secondary cell wall biosynthesis in Arabidopsis inflorescence stem

Secondary wall thickening in the sclerenchyma cells is strictly controlled by a complex network of transcription factors in vascular plants. However, little is known about the epigenetic mechanism regulating secondary wall biosynthesis. In this study, we identified that ARABIDOPSIS HOMOLOG of TRITHORAX1 (ATX1), a H3K4-histone methyltransferase, mediates the regulation of fiber cell wall development in inflorescence stems of Arabidopsis thaliana. Genome-wide analysis revealed that the up-regulation of genes involved in secondary wall formation during stem development is largely coordinated by increasing level of H3K4 tri-methylation. Among all histone methyltransferases for H3K4me3 in Arabidopsis, ATX1 is markedly increased during the inflorescence stem development and loss-of-function mutant atx1 was impaired in secondary wall thickening in interfascicular fibers. Genetic analysis showed that ATX1 positively regulates secondary wall deposition through activating the expression of secondary wall NAC master switch genes, SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN1 (SND1) and NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1). We further identified that ATX1 directly binds the loci of SND1 and NST1, and activates their expression by increasing H3K4me3 levels at these loci. Taken together, our results reveal that ATX1 plays a key role in the regulation of secondary wall biosynthesis in interfascicular fibers during inflorescence stem development of Arabidopsis.

Life cycle of arabidopsis in the international space station - Growth direction of the inflorescence stems in the presence of light under microgravity

ABSTRACTIn the “Space Seed” experiment performed in Kibo module of the International Space Station, growth direction of the inflorescence stem of arabidopsis was examined under space 1 G, μG, and ground 1 G conditions in the presence of light. The stems grew almost upright (vertical to the surface of seedbed) under ground 1 G. Although the stems were primarily upright both under space 1 G and μG, they tilted slightly. The tilting of the stems under space 1 G was indicated to be due to tilting of the artificial gravitational acceleration vectors produced on the centrifuge. The tilting of the stems under μG was suggested to be due to the pressure of directional airflow produced by ventilation.

Tissue-specific transcriptome profiling of the Arabidopsis thaliana inflorescence stem reveals local cellular signatures

Genome-wide gene expression maps with a high spatial resolution have substantially accelerated molecular plant science. However, the number of characterized tissues and growth stages is still small because of the limited accessibility of most tissues for protoplast isolation. Here, we provide gene expression profiles of the mature inflorescence stem of Arabidopsis thaliana covering a comprehensive set of distinct tissues. By combining fluorescence-activated nucleus sorting and laser-capture microdissection with next generation RNA sequencing, we characterize transcriptomes of xylem vessels, fibers, the proximal and the distal cambium, phloem, phloem cap, pith, starch sheath, and epidermis cells. Our analyses classify more than 15,000 genes as being differentially expressed among different stem tissues and reveal known and novel tissue-specific cellular signatures. By determining transcription factor binding regions enriched in promoter regions of differentially expressed genes, we furthermore provide candidates for tissue-specific transcriptional regulators. Our datasets predict expression profiles of an exceptional amount of genes and allow generating hypotheses toward the spatial organization of physiological processes. Moreover, we demonstrate that information on gene expression in a broad range of mature plant tissues can be established with high spatial resolution by nuclear mRNA profiling.One sentence summaryA genome-wide high-resolution gene expression map of the Arabidopsis inflorescence stem is established.