EFFECTS OF GLYPHOSATE ON GERMINATION AND PHOTOSYNTHESIS IN Prosopis alba G.: A BIOCHEMICAL APPROACH

In recent decades, the phytogeographic region of the Western Chaco has been subjected to heavy deforestation. The native forest was gradually replaced by agricultural crops using high doses of herbicides. Glyphosate is the most widely used herbicide, and its impact on the surrounding native flora is unknown. The aim of this work was to determine the effect of glyphosate on the germination of Prosopis alba seeds and the photosynthesis of seedlings. Seeds were placed between paper towels, moistened with solutions of 0, 10, 20, 20, 30 and 40 mg a.i. glyphosate l-1, in a growth chamber at 25 oC and a 12 h photoperiod. The percentage of germinated seeds and the mean germination time were calculated. The respiratory rate was measured in these seeds, and the activity of complexes I and III of the respiratory chain was quantified. The shikimate concentration and antioxidant response of the seeds were also quantified. Chlorophyll a fluorescence emission variables were measured in the cotyledons. It was concluded that glyphosate inhibits germination in P. alba seeds and decreases the speed of the process. This effect can partly be explained by inhibition of respiration, mainly at the level of complex III of the mitochondrial electron transport chain. It is also due to oxidative stress produced by the herbicide, since the antioxidant response of the seeds fails to compensate for the high production of reactive oxygen species. Glyphosate inhibits the photochemical stage of photosynthesis on P. alba cotyledons.

Growing season climate affects phenological development, seed yield and seed quality of dill (Anethum graveolens)

Dill seed production was investigated over two seasons, comprising a spring growing cycle (SGC) and an autumn growing cycle (AGC). The effects of growing cycle on phenological traits, yield and quality of dill seeds formed on different umbels of the mother plant were investigated. Significant differences were noted in the flowering period, seed yield and quality parameters. The SGC resulted in a shorter time from sowing to bolting and flowering initiation compared with the AGC. Plant height, number of umbels/plant, number of umbelets/umbel, umbel diameter, umbel length and seed weight/plant increased in the AGC. In contrast, decreased germination at 20/30°C and at 13°C, and increased mean germination time at 20/30°C in AGC indicated lower seed quality compared with SGC. Primary umbels produced the best yield and higher quality seeds, followed by the secondary umbels while tertiary umbels gave poor yield and quality seeds in both SGC and AGC. In conclusion, AGC was advisable for higher seed yield, but SGC resulted in higher seed quality compared with the AGC. This highlights the need to select a suitable growing cycle to guarantee high seed yield and quality for each seed production environment.

Interruption of Seed Dormancy and In Vitro Germination of the Halophile Emerging Crop Suaeda edulis (Chenopodiaceae)

Suaeda edulis (Flores Olvera & Noguez) is a halophile species that grows in saline environments, with concomitant difficulties to germinate and reproduce. Once a null germination under a salinity gradient or fresh water was observed, a plant-growth bioregulator (BioR) was applied to interrupt dormancy and improve germination in vitro. This BioR is composed of gibberellins and adjuvant regulators; and 12.5, 25.0, and 37.5 mg L−1 of gibberellins with immersion at 24, 48, and 72 h were assayed. Most of the normality and homoscedasticity tests were favorable, except in three of 24 cases. On the germination percentage (transformed values), the dose 25.0 mg L−1 reflected the highest values of 5.5 and 6.0 units at 48 and 72 h. For the mean germination time, the highest level of 37.5 mg L−1 at 24 h reflected the best response. For the germination rate, the best one was 25 mg L−1 at 48 h, reaching 12% per day, but for the germination speed coefficient, the best value was observed with 25.0 mg L−1 at 24 h. It was concluded that to improve germination of S. edulis seeds, it is necessary to assess a dose-gradient of gibberellins, starting at 25.0 mg L−1, with higher values to break dormancy.

Effects of pretreatment, sowing time, sowing environment and climate factors on germination in Acer pseudoplatanus L.

In this study, the effects of different sowing environment (greenhouse and nursery), pretreatment (cold moist stratification), different sowing time (autumn, spring and summer) and some climate factors (air temperature, relative air humidity, soil temperature and soil moisture) on the germination of Acer pseudoplatanus L. seeds were studied. Seeds were harvested from the tree located in the Karadeniz Technical University campus. Three different germination trials were carried out; (1) direct sowing in autumn after seed collection (Control), (2) sowing stratified seeds in spring (Stratification-1) and (3) sowing stratified seeds in summer (Stratification-2). During the germination trial processes, air temperature, relative air humidity, soil temperature and soil moisture were measured periodicaly. Thus, the germination percentage changes in different sowing environments have been established on the basis of some climate factors. Higher germination percentages were obtained in the autumn (Control) compared to the spring (Stratification-1) and summer (Stratification-2) sowings. The highest percentages of germination were ­determined in the control trials (70% in greenhouse and 58% in nursery). Obtained germination results based on different sowing times revealed secondary dormancy in Acer pseudoplatanus L. seeds. It has been determined that the mean germination time in the greenhouse (12 days) was shorter than the mean germination time in the nursery (18 days). In addition, the obtained results showed that stratification and sowing time have a positive effect on the mean germination time in the greenhouse. Because of getting the best germination rates, keeping some climate ­factors constant (21.0-24.9 °C air temperature; 17.0-19.9 °C soil temperature; 63.0-68.9% relative air humidity; 60.0-67.9% soil moisture) during the vegetative propagation practices in the greenhouse, should affect mass ­seedling production in Acer pseudoplatanus L.

Effect of Different Temperature Regimes on the Germination of Pseudolysimachion pusanensis (Y. N. Lee) Y. N. Lee Seeds

In this study, we determined the germination response in the seeds of the rare plant Pseudolysimachion pusanensis (Y. N. Lee) Y. N. Lee to different temperatures. P. pusanensis seeds were collected from the Baekdudaegan National Arboretum, South Korea, in November 2019, and dried. Dry seeds were placed at constant and alternating temperatures (5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, and 35 °C) to determine their germination percentage (GP). The seeds were exposed to 59 temperature combinations ranging from 5 °C to 43 °C using a thermal gradient plate. The photoperiod was set at 12:12 h (light:dark) and germination assays were performed five times a week. Subsequently, the seed GP and the number of days required to reach 50% of the germination (T50) were determined. The highest final GP was 94.38%, with a T50 value of 9.26 d at 15 °C. However, the mean germination time was 12.5 d at 15 °C, and linear regression using 1/T50 revealed that the base temperature ranged from 2.69 °C to 4.68 °C. These results for P. pusanensis seeds stored in a seed bank provide useful data for the native plants horticulture industry and can also be utilized for storage management.

Germination and morphological responses of Triticum aestivum L. to different concentrations of fluoride

A laboratory experiment was conducted on germination papers to study the effect of fluoride (F) at 0 (T1), 50 (T2), 100 (T3), 200 (T4), 250 (T5) and 300 (T6) ppm on germination and morphological parameters in wheat (Triticum aestivum L.) variety, HUW-234 at 2, 4 and 6 days after initiation of germination process. Fluoride toxicity caused reduction in germination per cent, germination index, coefficient of velocity of germination and germination energy (%) while mean germination time increased with fluoride concentration. Root and shoot lengths and dry matters decreased with increased concentrations of fluoride. Ratio of root: shoot weight increased with increased concentration of fluoride. Elongation of seminal roots was adversely affected by increased fluoride level. Increased fluoride level in the germination medium decreased RGR of seedlings progressively. Present study revealed that enhanced fluoride concentration in germination medium caused reduction in germination and germination related parameters.

Seed germination response of Indian wild pear (Pyrus pashia) to gibberellic acid treatment and cold storage

Knowledge of seed germination behaviour of different seed sources of tree species is useful in selecting the most responsive and adaptive ones for propagation and germplasm conservation. The wild Himalayan pear (Pyrus pashia Buch-Ham ex D. Don) produces highly nutritious edible fruits that are consumed by local communities. The populations of the species are threatened due to exploitation and lack of adequate conservation programmes. The study was conducted to examine the germination response of P. pashia seeds from two sources (S1-Champawat and S2-Pithoragarh) in Uttarakhand state of India, to different GA3 treatment and also to assess the viability and longevity of the seeds in cold storage (5 °C) for three years. In both sources germination percent (GP) increased significantly under GA3 treatment and speed of germination was also enhanced (reduction in mean germination time). In Source, 1 GP increased under all GA3 application, highest being 94% under GA3 500 ppm treatment. In Source 2, GP of seeds doubled under 100 ppm GA3 treatment while its higher concentrations did not improve the germination. However, the differences observed in germination between the seed sources could be due to differences in the dormancy levels and/or sensitivity to dormancy breaking elements across their geographical range. Thus, exogenous application of GA3 is suggested for enhancing the germination in seeds of P. pashia. Seeds responded to cold storage by increased germination with duration, i.e. highest after three years in storage, indicating that the seeds got the required chilling treatment for overcoming dormancy.

Germination and Seedling Parameters of Wheat as Affected by Storage Conditions

A storage experiment was carried out from 27th April to 27thDecember, 2019 to study the effect of storage conditions i.e. methods (open air, under sunshade and in stores), packages type (normal, gunny, polyethylene and metal containers) and periods of seeds fumigation with phosphine (15, 30 and 45 days) on germination and seedling parameters of wheat. The experiment was arranged in a factorial experiment in randomized complete block design (R.C.B.D.) with four replications. Stored wheat seeds under sunshade produced the highest values of final germination percentage, germination index, mean germination time, plumule length, radical length, seedling vigor index and seedlings dry weight, followed by stored wheat seeds in stores. The highest germination index, mean germination time, plumule and radical lengths, seedling vigor index and seedlings dry weight were recorded in the samples of wheat seeds sealed stored in metal containers, followed by normal stored in gunny packages. The highest percentage of final germination was obtained by normal stored in gunny packages, followed by sealing storage in metal containers. The highest final germination percentage, germination index, mean germination time, plumule length, radical length, seedling vigor index and seedlings dry weight and the lowest abnormal seedlings percentage, rotten and sold seeds percentages, speed germination index, co-efficient of germination and germination energy percentage were recorded when treated with phosphine at the rate of 3 tablets/m3after 15 days from beginning the storage. This study recommended that stored wheat seeds under sunshade in metal packages and treating with phosphine at the rate of 3 tablets/m3 after 15 days from beginning the storage to enhance germination and seedlings parameter of wheat under the environmental conditions of Dakahlia Governorate, Egypt.

Differences in the Seed Germination of Leymus chinensis (Poaceae) Ecotypes Reveal Distinct Strategies for Coping With Salinity Stress: A Common Garden Experiment

Soil salinity is important abiotic stress affecting various ecosystems worldwide such as grassland. Distinct ecotypes often evolve within species by natural selection to facilitate adaptation to different types of environmental stress. Leymus chinensis is a perennial rhizomatous grass that is widely distributed in the eastern Eurasian steppe; it has two main ecotypes, namely, yellow-green (YG) and gray-green (GG), which differ in their strategy for coping with salinity stress. Few studies have examined the seed germination of the two ecotypes under salinity stress. In this study, the seed germination and seedling growth of two ecotypes of L. chinensis in response to different levels of salinity (NaCl) stress [0 (control), 20, 50, 100, and 200 mM] were examined. Then, ungerminated seeds were placed under normal conditions to evaluate seedling growth following exposure to salt stress (i.e., regermination). The germination percentage was significantly higher, and the mean germination time was significantly shorter in the GG ecotype than in the YG ecotype at all NaCl concentrations. As the salinity level increased, the radicle length of the two ecotypes decreased; however, GG had longer radicles and a higher number of radicles, even at 200 mM NaCl when no radicle protruding from the seed coat was detected in YG. The shoot length of GG was significantly longer than that of YG at all NaCl levels. After salinity stress was removed, the seed germination percentage increased as the original concentration of NaCl applied increased, but the total germination percentage did not significantly differ among NaCl concentrations. The total seed germination percentage of GG was approximately 80%, whereas that of the YG was approximately 20%. The seedling length of regerminated seeds for both GG and YG was similar. The thousand-grain weight of GG was significantly higher than that of YG. GG was more salt-tolerant than YG and might be better capable of surviving in harsher environments, suggesting that GG might be particularly useful for saline grassland restoration.

Substrate and temperature on seed germination of Aspidosperma vargasii A. DC. (Apocynaceae)

The Amazon has a wide diversity, including forest species with timber and non-timber potential, which often have their use restricted due to a lack of silvicultural information. Thus, the present study aimed to evaluate the effect of substrates and temperatures on seed germination of Aspidosperma vagarsii. Therefore, the premise of a completely randomized design was followed, in a 3 x 3 factorial scheme, with three substrates (paper, sand and vermiculite) and three temperatures (20, 25 and 30 °C). The germination percentage, germination speed index and mean germination time were determined, as well as germination relative frequency graphs. In addition, the weight of a thousand seeds, the number of seeds per kilo, and the moisture content was determined. The weight of thousand seeds was equal to 276.4 g, with 3,618 seeds per kilo, and a moisture content of 9.5%. There was no interaction between the studied factors. The sand substrate and temperatures of 20 and 25 °C presented the best results for seed germination of A. vargasii.