Use of hydrogel in the irrigation management of white pitaya (Hylocereus undatus) seedlings: Biometrics and accumulation of organic and inorganic solutes

The initial development of pitayas may be limited by a few factors, among them, water deficit. Agricultural hydrogels can be used as an alternative to enhance the retention and availability of water and nutrients in the soil. Therefore, this study aimed to evaluate the influence of irrigation frequency and hydrogel doses on the development of white pitaya (Hylocereus undatus) seedlings to establish a time interval in days between irrigations that provides better seedling development and determine the hydrogel dose that provides a reduction of water consumption without damaging seedling development. The experimental design consisted of randomized blocks in a 4 x 4 factorial arrangement, in which the treatments corresponded to 4 hydrogel doses (0, 2, 4, and 6 g/plant of Biogel Hidro Plus) incorporated into the substrate and four irrigation frequencies (1, 3, 5, and 7 days of interval). The biometric characteristics, photosynthetic pigments, and organic and inorganic solutes of the plants were evaluated after 120 days. The use of daily irrigation negatively influenced the growth and biomass accumulation of the aerial part of the seedlings and, consequently, provided the lowest values of cladodes of the pitaya seedlings. Pitaya seedlings had greater development when using an irrigation frequency of around 3 days. The application of 6 g/plant of hydrogel provided the highest averages for accumulation of dry biomass, photosynthetic pigments, and organic and inorganic solutes at irrigation levels of 3.6, 4, and about 3.8 days of intervals, respectively. Hydrogel incorporation allowed increasing the interval between irrigations by 1 day without damages to the seedling development.

Filtrates from cultures of endophytic fungi isolated from leaves of Copaifera oblongifolia (Fabaceae) affect germination and seedling development differently

Interactions between endophytic fungi (EFs) and their host plants range from positive to neutral to negative. The results of such interactions can vary depending on the organ of the infected host plant. EFs isolated from the leaves of some species of plants have potential for use as agents to inhibit seed germination and control invasive plants. The objectives of this study were to identify EFs present in the leaves of Copaifera oblongifolia and to evaluate the role of these fungi in seed germination and seedling development. A total of 11 species of EFs were isolated, which were identified using the internal transcribed spacers (ITS) sequence of the nuclear ribosomal DNA. The isolated species of EFs are generalists and probably are transmitted horizontally. Laboratory tests revealed that filtrates of these fungal isolates differently affect seed germination and seedling development of C. oblongifolia. The species Curvularia intermedia, Neofusicoccum parvum, Pseudofusicoccum stromaticum and Phomopsis sp. negatively affected seed germination, with N. parvum standing out for its negative effects, inhibiting seedling germination and survival in 89 and 222%, respectively. In addition, Cochliobolus intermedius negatively affected seedling development. Thus, the combined use of N. parvum and C. intermedius, or products from the metabolism of these microorganisms, in the control of invasive plants deserves attention from future studies.

Biphasic control of cell expansion by auxin coordinates etiolated seedling development

Auxin concentration–dependent cell expansion coordinates hypocotyl elongation and apical hook development for soil emergence.

Seasonal variation of the effect of extremely diluted agitated gibberellic acid (10-30) on wheat seedling development

Objective: Performing a study on a wheat growth bio assay with a homeopathic dilution of gibberellic acid at different seasons of the year. Methods: Grains of winter wheat (Triticum aestivum, Capo variety) were observed under the influence of extremely diluted gibberellic acid (10-30, 30x). Analogously prepared water was used for control. 15 experiments were performed, 9 in autumn season (5 researchers, 4,440 grains per group), and 6 in winter / spring (4 researchers, with 3,140 grains per group). Results: All 9 autumn experiments showed less stalk growth in the verum group (p > 0.01 in 4 cases, p > 0.05 in 3, trend in 2 cases). Mean stalk lengths (mm) were 46.97 + 20.50 for verum and 50.66 + 19.77 for control at grain level (N = 4,440 per group) and + 3.87 and + 3.38 respectively at dish level (217 cohorts of 20 or 25 grains per treatment group). Verum stalk length (92.72%) was 7.28% smaller than control stalk length (100%). In contrast, no reliable effect was found in experiments performed in winter / spring (less stalk growth in 1 case, no difference in 1, more growth in 3 cases). Overall verum stalk length (103.64%) was 3.64% slightly greater than control stalk length (100%). Data were found to be homogeneous within the control groups as well as within the verum groups. Conclusion: Results suggest that especially in the experiments performed in autumn, there was an influence of gibberellic acid 30x on wheat seedling development. The effect size is small when calculation is done on the basis of grains (d = 0.18) but high when done on the basis of dishes (d = 1.02). In contrast, no reliable effect was found in experiments performed in winter / spring. Further experiments should thus be performed in the autumn season.

SUBSTRATE MIXING FORMULATIONS FOR CITRUS NURSERY MANAGEMENT

The length of citrus seedling development is determined by several factors, including the physical and chemical qualities of the substrate, which affect rootstock growth and, as a result, the quality of field seedlings. The purpose of this study was to see how the ‘Swingle’ citrumelo rootstock developed with different substrate formulations. The experiment was carried out in a seedling nursery from seeding to grafting, and six treatments were carried out, as follows: 60% peat moss, 30% fine grade horticultural vermiculite, 10% rice hulls (1); 60% peat moss, 30% fine grade horticultural vermiculite, 10% rice hulls (2); 50% peat moss, 30% fine grade horticultural vermiculite, 20% rice hulls (3); 50% peat moss, 30% fine grade horticultural vermiculite, 20% rice hulls (4); 50% peat moss, 20% fine grade horticultural vermiculite, 30% rice hulls (5); 50% peat moss, 20% fine grade horticultural vermiculite, 30% rice hulls (6). In addition, the experiment was divided into two stages: seeding (stage 1) and seedling nursery (stage 2). In a completely randomized design, the experiment has six treatments, four replications, and 51 plants per plot. When container transplanting was performed, the emergence percentage of seedlings was determined; thus, eight plants per plot were examined. For the second stage, was used a completely randomized design with 6 substrate formulations, 4 replications, and 20 seedlings per plot. Stem height, stem diameter, leaf number, area meter, root dry matter, leaf and stem dry matter, and quality index were measured on seedlings every 28 days. All substrate formulations improved seedling development until grafting, except for the 30% rice hulls, which hampered seedling development in ‘Swingle' citrumelo.

Impact of non-thermal plasma treatment on the seed germination and seedling development of carrot (Daucus carota sativus L.)

Seed germination is a complicated physiological process that starts with the seed absorbing water and concludes with the radicle emerging. The kinetics and amount of water uptake by seeds are known to be influenced by both seed surface properties and the surrounding environment. As a result, altering seed surface features are linked to seed medium and is a valuable strategy for controlling seed germination. In the agricultural field, non-thermal plasma surface activation of seeds is currently being investigated as an efficient pre-sowing treatment for modifying seed germination. The impact of non-thermal plasma (NTP) on the germination and seedling growth of carrot seeds at room temperature and atmospheric pressure for varied treatment times was investigated in this study. Seed's germination properties and growth parameters were examined for both control and NTP treated seeds. Germination-related parameters such as germination percentage, vigor index, and chlorophyll content were all improved by NTP treatment. However, no significant changes were seen in the carotenoid content. Similarly, the in-vitro radical scavenging activities, total phenol, and total flavonoid contents in the seedlings were altered by NTP treatment. Our results indicate that NTP treatment has a favorable effect on carrots germination and seedling development.

BBX16 mediates the repression of seedling photomorphogenesis downstream of the GUN1-GLK1 module during retrograde signaling

Plastid-to-nucleus retrograde signals (RS) initiated by dysfunctional chloroplasts impact photomorphogenic development. We previously showed that the transcription factor GLK1 acts downstream of the RS-regulator GUN1 in photodamaging conditions to regulate not only the well-established expression of photosynthesis-associated nuclear genes (PhANGs) but also to regulate seedling morphogenesis. Specifically, the GUN1/GLK1 module inhibits the light-induced PIF-repressed transcriptional network to suppress cotyledon development when chloroplast integrity is compromised, modulating the area exposed to potentially damaging high light. However, how the GUN1/GLK1 module inhibits photomorphogenesis upon chloroplast damage remained undefined. Here, we report the identification of BBX16 as a novel direct target of GLK1. BBX16 is induced and promotes photomorphogenesis in moderate light and it is repressed via GUN1/GLK1 after chloroplast damage. Additionally, we show that BBX16 represents a regulatory branching point downstream of GUN1/GLK1 in the regulation of PhANG expression and seedling development upon RS activation. The gun1 phenotype in lincomycin and the gun1-like phenotype of GLK1OX are markedly suppressed in gun1bbx16 and GLK1OXbbx16. This study identifies BBX16 as the first member of the BBX family involved in RS, and defines a molecular bifurcation mechanism operated by GLK1/BBX16 to optimize seedling deetiolation, and to ensure photoprotection in unfavorable light conditions.