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.

Lanthanum delays senescence and improves postharvest quality in cut tulip (Tulipa gesneriana L.) flowers

We tested two sources of lanthanum (La), LaCl3 and La(NO3)3 × 6H2O at a concentration of 40 µM each, in the treatment solution of cut flowers of 15 tulip (Tulipa gesneriana L.) cultivars. Ascorbic acid (AsA; 0.2 g/L) was used as a reference solution, while distilled water was evaluated as an absolute control. With both La sources, bud length and diameter, and stem length were increased; as a result, stem curvature was also significantly increased with La treatments. The cultivars Laura Fygi and Rosario registered the highest relative stem elongation. Lalibela and Acropolis displayed the greatest stem curvature on the last day in vase. At 3, 5, 7, 9 and 11 days after cutting, the highest solution uptake was recorded in flower stems treated with LaCl3, surpassing the control by 5, 11, 15, 18 and 24%, respectively. The relative stem elongations observed were 21.3, 27.4, 35.2 and 35.5% in the control, AsA, LaCl3 and La(NO3)3, respectively. The mean solution uptake per gram of stem fresh biomass weight was 1.44, 1.44, 1.71 and 1.54 mL in the control, AsA, LaCl3 and La(NO3)3, respectively. LaCl3 significantly increased the bud length and solution uptake of flower stems, while La(NO3)3 × 6H2O increased stem fresh weight.

Contributions of bark and tension wood and role of the G-layer lignification in the gravitropic movements of 21 tropical tree species

Key message Gravitropic movements in angiosperm woody stems are achieved through the action of bark and/or wood motor, depending on the bark and wood fibre anatomy (with trellis structure or not; with G-layers or not). Bark motor is as efficient as wood motor to recover from tilting in young trees of 21 tropical species. Context Angiosperm trees produce tension wood to control their orientation through changes in stem curvature. Tension wood is classified into 3 anatomical groups: with unlignified G-layer, with lignified G-layer and without G-layer. Aims This study aimed at assessing whether this anatomical diversity reflects a diversity in efficiency of gravitropic movement. Methods The study was conducted on tropical seedling from the three anatomical groups. Seedlings were staked and grown tilted. At the end of the experiment, changes in curvature when releasing the stem from the stake and when removing bark were measured. Three parameters were computed to compare the global efficiency of gravitropism (stem gravitropic efficiency) and the specific efficiency of motor mechanism based on wood (maturation strain of tension wood) and bark (standardized debarking curvature). Results The maturation strain of tension wood was similar between species with unlignified and lignified G-layer. Species without G-layer exhibited low maturation strain and large debarking curvature, showing they rely on bark for gravitropism. Bark and wood achieved similar motor efficiency. Conclusion Lignin does not affect the generation of tensile stress in the G-layer. Bark can be as efficient as wood as a motor of gravitropic movements.

Reconstruction of Landslide Activity Using Dendrogeomorphological Analysis in the Karavanke Mountains in NW Slovenia

Tree ring eccentricity was used to reconstruct landslide activity in the last 138 years in the Urbas landslide located at Potoška planina in the NW part of the Karavanke Mountains, Slovenia. The research was based on the dendrochronological sampling of Norway spruce (Picea abies (L.) Karst.) in areas of varying landslide intensity. Analysis of a sudden change in the eccentricity index of 82 curved trees concluded that there were 139 growth disturbances and 16 landslide reactivations between 1880 and 2015, with a landslide return period of 8.5 years. Using lidar data, changes in the surface of the digital terrain model (DTM) were compared with changes in the eccentricity index of trees at the same location in the period 2014–2017. On the basis of temporal changes in the eccentricity index and by using spatial interpolation, landslide activity was reconstructed for the period 1943–2015. During this period, landslide intensity increased in the central part of the landslide. Although categorization into seven categories of different stem curvature was proposed, no distinction between categories with respect to their eccentricity index was found.

Is the Responsiveness to Light Related to the Differences in Stem Straightness among Populations of Pinus pinaster?

Stem straightness is related to wood quality and yield. Although important genetic differences in stem straightness among the natural populations of Pinus pinaster are well established, the main drivers of these differences are not well known. Since the responses of trees to light are key ecological features that induce stem curvature, we hypothesized that populations with better straightness should exhibit lower photomorphogenetic and phototropic sensitivity. We compared three populations to identify the main processes driven by primary and secondary growth that explain their differences in response to light. One-year-old seedlings were grown under two treatments—direct sunlight and lateral light plus shade—for a period of 5 months. The length and the leaning of the stems were measured weekly. The asymmetry of radial growth and compression wood (CW) formation were analyzed in cross-sections. We found differences among the populations in photomorphogenetic and phototropic reactions. However, the population with straighter stems was not characterized by reduced sensitivity to light. Photo(gravi)tropic responses driven by primary growth and gravitropic responses driven by secondary growth explained the kinetics of the stem leaning and CW pattern. Asymmetric radial growth and CW formation did not contribute to the phototropic reactions.

Maintenance solutions for the conservation of sunflower inflorescences

The sunflower (Helianthus annuus L.) is an ornamental plant of great acceptance in the market, however, as cut flower has its limited useful life, about 3 to 5 days at room temperature. In order to prolong shelf life and preserve post-harvest quality was evaluated the effect of maintenance solutions on sunflower cv. Oasis for 10 days storage at 25 °C. O experimento foi conduzido em delineamento inteiramente casualizado em arranjo fatorial 5x6, correspondendo a cinco tratamentos/soluções de manutenção (distilled water (control), sucrose, citric acid, gibberellic acid and benzylaminopurine to 5%) and six evaluation times (0, 2, 4, 6, 8 and 10 days). The effect of treatments on fresh mass, inflorescence turgescence, stem curvature, relative petal water content, respiratory rate and carbohydrate content was investigated. The results showed that the solutions with sucrose and gibberellic acid significantly (p<0.05) preserved the quality of the inflorescences as a function of the control of respiratory activity and water absorption, thereby reducing the physiological processes related to senescence. It is recommended to use sucrose 5% as a maintenance solution due to the low cost to producers and consumers.

Postharvest Quality of Cut Roses With the Application of Salicylic Acid

The objective of this work was to evaluate the effect of the application of salicylic acid (SA) on the maintenance of quality and longevity of cut roses cv. Vega. Cut roses were kept in a vase solution of SA and water at concentrations of 0; 0.5; 1.0; 1.5 and 2.0 mM. All treatments were kept at 8±2 oC for 96 hours, simulating storage in flower shops; the flowers were then evaluated regarding loss of fresh matter and leaf chlorophyll content and were transferred to beakers containing distilled water at 25±2 ºC for more 144 hours, simulating shelf life. At 24, 48, 72 and 96 hours from the beginning of the experiment, biochemical analyses of total proteins and the activity of the phenylalanine ammonia-lyase (PAL) and peroxidases (PO) were performed. Visual analyses were performed (stem curvature, turgescence and petal darkening) every 48 hour intervals until the end of the experiment. The treatments with SA allowed the maintenance of post-harvest quality, reducing the loss of fresh matter mass, lower stem curvature, greater turgescence and less darkening of the petals. The results showed that the application of SA increased total protein contents and FAL, which characterizes the activation of plant defense mechanisms to the senescence process.

Peculiar traits of wood in a leaning stem of Scots pine (Pinus sylvestris L.)

The paper analyses biometrical and anatomical traits of wood in a leaning stem of pine trees. For study purpose, five pine trees (Pinus sylvestrisL.) with a visibly leaning stem were chosen. Wood samples were taken at three different stem heights, that is, below the stem curvature, at the curvature and above the curvature. Microscopic specimens were prepared and used for the following measurements: annual rings width, tracheids diameter and tracheids wall thickness. The measurements were performed for wood located on the lower side of the leaning stem and on the opposite side. Cytochemical staining was performed to identify the occurrence of laricinan. The results showed tracheids with a rounded shape and thick cell walls, helical cavities and intercellular spaces in wood located at curvature height on the lower side of the leaning stem. These traits indicate a severe compression wood that allowed pine trees to change their stem position in relation to the vector of gravity.

Prosperity of Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) plantations in relation to the shelter

The study evaluates the mortality, growth and qualitative characteristics of Douglas fir transplants planted out on clear-cut areas with different shelter. We assessed 11 clearings situated in the Forest Site Complex 4K &ndash; acidic beech (Fagetum acidophilum). The young trees were assessed 3 years after planting for the following parameters: total shoot length, increment, root collar diameter, number of multiple stems, stem curvature, crown form, length of needles, colour of needles and frost damage. The lowest mortality and the best growth of Douglas fir plants were recorded in small, sheltered gaps. Large, unsheltered gaps showed low survival, slower growth and poor vitality of plants. &nbsp;