Characterizing the effects of different chemicals on stem bending of cut snapdragon flower

Background This study investigated the effects of ethylene release compounds (ethephon), ethylene-action inhibitors (silver thiosulfate: STS), and nitric oxide donor (sodium nitroprusside: SNP) on stem bending of snapdragon flowers. Moreover, the effects of plant growth supplements [6-benzyladenine (BA), gibberellic acid 3 (GA3), and calcium chloride (CaCl2)] on the stem bending were also extensively investigated. Results Ethephon completely prevented stem bending until 9 days after treatment (9 DAT). STS exhibited the highest bending rate, while SNP did not significantly affect the bending compared to the controls. The bending results were associated with the results of stem curvature, relative shoot elongation, ethylene production, and lignin content, that are involved in the stem bending mechanism. This was proven by the expression analysis of genes involved in ethylene and lignin biosynthetic pathways. The addition of plant growth supplements slightly or significantly delayed stem bending in the treatments (control, SNP, and STS) and significantly reduced petal senescence in ethephon at 9 DAT. Conclusion These results show the preventive role of ethephon in the stem bending of cut snapdragon. Moreover, the combination of ethephon with supplements also provided information that could guide the development of strategies to delay stem bending in other cut flowers that undergo serious bending during a short vase life.

Ethylene Acts as a Negative Regulator of the Stem-Bending Mechanism of Different Cut Snapdragon Cultivars

This study investigated whether ethylene is involved in the stem-bending mechanism of three different snapdragon cultivars ‘Asrit Red’, ‘Asrit Yellow’, and ‘Merryred Pink’, by treating their cut stems with an ethylene-releasing compound (ethephon), an ethylene-action inhibitor [silver thiosulfate (STS)], and distilled water (as the control). Ethephon completely prevented stem bending in all cultivars, whereas STS exhibited a higher bending rate compared with the control. The bending rates were influenced by several factors, such as the degree of stem curvature, relative shoot elongation, ethylene production, and lignin content, indicating their involvement in the stem-bending mechanism of the cultivars. The analysis of the expression of genes involved in the ethylene and lignin biosynthetic pathways also supported the importance of lignin and ethylene in the stem-bending mechanism. Taken together, as ethephon completely prevented stem bending of the three snapdragon cultivars, this study suggested that ethylene acts as a negative regulator of the stem-bending mechanism of snapdragon cultivars, and the information will be valuable for the prevention of stem bending in other commercially important ornamental flowers.

Silica nanoparticles and calcium on the histological characteristics and stem bending in gerbera cut flower

Silica nanoparticles and calcium are necessary for improving plant yield and decreasing stem bending in gerbera flower (Gerbera Jamesonii L.). In order to determine the optimal concentrations of silica nanoparticles and calcium in gerberas (Gerbera Jamesonii L.), a factorial experiment in the form of completely randomized design with two factors was conducted. The first factor was the concentration of silica nanoparticles (Nanoparticle-SiO2) at four rates (0, 20, 40, and 80 mg L-1) and the second factor was the concentration of calcium chelate (Ca-Chelate) at four rates (0, 60, 120, and 240 mg L-1) which were applied as nutrient solutions. After harvest, characteristics such as stem bending, cellulose content, phenyl alanine ammonia-lyase enzyme activity in leaves, and stem histological characteristics were measured. Results indicated that the lowest stem bending (deviation angle of 8.78°) was observed with applying 20 mg L-1 Nanoparticle-SiO2 and 240 mg L-1 Ca-Chelate. Comparing with control, applying 80 mg L-1 Nanoparticle-SiO2 and 240 mg L-1 Ca-Chelate increased lignin and cellulose contents by 33 and 15%, respectively. The highest amount of phenylalanine ammonia-lyase (2.87 units per mg of fresh leaf) was obtained by using 60 mg L-1 calcium chelate. According to nutrient concentrations, the change patterns of xylem and stem lignification were different, which is in line with the results of the physiological studies conducted on the effects of applying silica nanoparticle and calcium in nutrient solution. Under the epidermis, there was a hypodermis (sclerenchyma) which strengthens stem tissue. Silica nanoparticles and calcium chelate due to increasing phenylalanine ammonia-lyase content and its effect on the production cycles of cellulose and lignin and increasing stem sclerenchyma, led to stems strength and lignification, which eventually decreased stem bending. According to study results, applying 40 mg L-1 Nanoparticle-SiO2 and 60 mg L-1 Ca-Chelate in hydroponic nutrient solution is recommended for growing gerbera flowers.

MORPHOMETRIC CHANGES AND POST-PLANTING GROWTH AS A RESPONSE TO HARDENING ON Tabebuia roseo-alba SEEDLINGS

The essay evaluated morphometric changes in response to stem bending and jasmonic acid on Tabebuia roseo-alba (Ridl). Sand. seedlings. We tested 20 daily stem bendings and applications of 1 μmol L-1 of jasmonic acid for 4 or 8 weeks. Stem bending for 8 weeks resulted in seedlings with fewer leaves and smaller shoot dry biomass compared to seedlings subjected to the other treatments. The results of electrolyte leakage from root tissues of control seedlings showed higher value compared to results from seedlings subjected to the test treatments. After planting, we did not detect differences in height and diameter increments from seedlings subjected to the test treatments. Therefore, hardening methods did not improve post-planting seedling growth.

Silencing of The Slzf-31 Gene Decreases The Salt Stress Tolerance And Drought Tolerance Of Tomato

The SlZF-31 gene is a member of the tomato C2H2 transcription factor family. Previous studies have shown that SlZF-31 gene expression is upregulated under drought stress and salt stress, but the specific function of this gene in tomato plants in response to these two kinds of stress is still unclear. To further explore the function of the SlZF-31 gene in tomato under drought stress and salt stress, we employed the virus-induced gene silencing (VIGS) method to reduce the expression of the SlZF-31 gene in tomato. The results showed that TRV2-SlZF-31 plants had higher levels of wilt and stem bending than CK and CK-TRV2 plants under drought and salt stress. The ABA content of TRV2-SlZF-31 plants were lower than those of CK and CK-TRV2 plants. The analysis of physiological indexes showed that the SOD and POD activity and the PRO content of TRV2-SlZF-31 plants were lower than those of CK and CK-TRV2 plants, while the MDA content of TRV2-SLlZF-31 plants was higher than those of CK and CK-TRV2 plants. The accumulation of H2O2 and O2- in TRV2-SlZF-31 plants was greater than those in CK and CK-TRV2 plants. The values of the chlorophyll fluorescence parameters (ΦII and qL) of TRV2-SlZF-31 plants were significantly lower than those of CK and CK-TRV2 plants. These results showed that the silencing of the SlZF-31 gene reduces the drought resistance and salt tolerance of tomato.

Early transcriptional response to gravistimulation in poplar without phototropic confounding factors

Background and Aims In response to gravistimulation under anisotropic light, tree stems showing an active cambium produce reaction wood that redirects the axis of the trees. Several studies have described transcriptomic or proteomic models of reaction wood relative to the opposite wood. However, the mechanisms leading to the formation of reaction wood are difficult to decipher because so many environmental factors can induce various signaling pathways leading to this developmental reprogramming. Using an innovative isotropic device where the phototropic response does not interfere with gravistimulation we characterized the early molecular responses occurring in the stem of poplar after gravistimulation in an isotropic environment, and without deformation of the stem. Methods After 30 minutes tilting at 35° under anisotropic light, we collected the upper and lower xylems from the inclined stems. Controls were collected from vertical stems. We used a microarray approach to identify differentially expressed transcripts. High throughput real-time PCR allowed a kinetic experiment at 0, 30, 120 and 180 minutes after tilting at 35°, with candidate genes. Key Results We identified 668 differentially expressed transcripts, from which we selected 153 candidates for additional fluidigm qPCR assessment. Five candidate co-expression gene clusters have been identified after the kinetic monitoring of the expression of candidate genes. Gene-ontology analyses indicate that molecular reprogramming of processes such as “wood cell expansion”, “cell wall reorganization” and “programmed cell death” occur as early as 30 minutes after gravistimulation. Of note is that the change in the expression of different genes involves a fine regulation of gibberellin and brassinosteroid pathways as well as flavonoid and phosphoinositide pathways. Conclusions Our experimental setup allowed the identification of genes regulated in early gravitropic response without the bias introduced by phototropic and stem bending responses.