Seed germination ecology of Conyza sumatrensis populations stemming from different habitats and implications for management

Conyza sumatrensis (Retz.) E. H. Walker is an obnoxious weed, emerging as an invasive species globally. Seed germination biology of four populations of the species stemming from arid, semi-arid, temperate, and humid regions was determined in this study. Seed germination was recorded under six different environmental cues (i.e., light/dark periods, constant and alternating day and night temperatures, pH, salinity, and osmotic potential levels) in separate experiment for each cue. Populations were main factor, whereas levels of each environmental cue were considered as sub-factor. The impact of seed burial depths on seedling emergence was inferred in a greenhouse pot experiment. Seed germination was recorded daily and four germination indices, i.e., seed germination percentage, mean germination time, time to reach 50% germination, and mean daily germination were computed. Tested populations and levels of different environmental cues had significant impact on various seed germination indices. Overall, seeds stemming from arid and semi-arid regions had higher seed germination potential under stressful and benign environmental conditions compared to temperate and humid populations. Seed of all populations required a definite light period for germination and 12 hours alternating light and dark period resulted in the highest seed germination. Seed germination of all populations occurred under 5–30°C constant and all tested alternate day and night temperatures. However, the highest seed germination was recorded under 20°C. Seeds of arid and semi-arid populations exhibited higher germination under increased temperature, salinity and osmotic potential levels indicating that maternal environment strongly affected germination traits of the tested populations. The highest seed germination of the tested populations was noted under neutral pH, while higher and lower pH than neutral had negative impact on seed germination. Arid and semi-arid populations exhibited higher seed germination under increased pH compared to temperate and humid populations. Seed burial depth had a significant effect on the seedling emergence of all tested populations. An initial increase was noted in seedling emergence percentage with increasing soil depth. However, a steep decline was recorded after 2 cm seed burial depth. These results indicate that maternal environment strongly mediates germination traits of different populations. Lower emergence from >4 cm seed burial depth warrants that deep burial of seeds and subsequent zero or minimum soil disturbance could aid the management of the species in agricultural habitats. However, management strategies should be developed for other habitats to halt the spread of the species.

Sugar beet (Beta vulgaris L.) germination indices and physiological properties affected by priming and genotype under salinity stress

Seed priming has proved to be an effective method in imparting stress tolerance to plants using natural and/or synthetic compounds to treat the seeds before germination. The present study was designed to investigate the physiological mechanism of seed priming with ZnSO4 (osmopriming) and distilled water (hydropriming) on sugar beet genotypes (‘Shokofa’, ‘Sina’, ‘Paya’, ‘Turbata’, and ‘Aria’) germination indices, seedling growth parameters, and biochemical properties under salinity stress (0, 2, 5, and 12 dS/m NaCl). A significant reduction in germination percentage (33.23%), germination rate (77.2%), chlorophyll a, b, and total contents (43.9, 31.9, and 39.9%, respectively) while, a significant increase in radical, plumule, and seedling length (57.1, 44.4, and 51.2%, respectively), seedling vigour index (48.9%), superoxide dismutase activity (61.3%), proline (54.0%) and sugar (56.3%) contents were achieved at 12 dS/m NaCl in compared to the control treatment. Seed hydropriming and osmopriming caused significant improvements in photosynthetic pigments, antioxidant enzyme activity, and proline content reflected in high germination percentage and rate as well as seedling vigour index and reduced mean germination time under salinity. ‘Paya’ and ‘Aria’ genotypes had a superiority according to the germination percentage and seedling vigour index, respectively. The hydropriming of ‘Paya’ genotype resulted in the highest germination percentage (95%) under high level of salinity (12 dS/m) which 11.84% increase compared to the control treatment. Hydropriming of ‘Sina’ seeds showed the highest chlorophyll a and total, and carotenoids under non-stress conditions (22.89, 31.65, and 2116.6 µg/g FW). Also, hydropriming by increases chlorophyll b content led to the modulation of the negative effects of high salinity stress (12 dS/m). In conclusion, different seed priming treatments in sugar beet seeds improved the salinity tolerance by physiological characteristics nonetheless hydropriming was the most effective treatment to get higher germination indices in ‘Paya’ and ‘Aria’ genotypes.

Performance Testing of NaCMC/HPC/NaAlg Hydrogels for Agricultural Applications

Physically cross-linked NaCMC/HPC/NaAlg hydrogel beads were subjected to several performance tests to determine their ability to mitigate the immediate impacts of drought and their effectiveness to control nutrient release in soil. The tests showed that the beads have a water absorption capacity of 2438%, indicating superabsorbent capability. Reusability tests showed that they are capable of at least six cycles of swelling/deswelling with a net decrease in swelling from 331% to 170%. Nutrient release studies were done using a multistage diffusion model to examine their effectiveness in controlled release. Soil amendment studies showed that a 2.65% increase in the maximum water holding capacity is obtained per 0.1% of hydrogels in soil. Furthermore, phytotoxicity studies showed that the germination indices of representative vegetable crops planted in hydrogel-treated soil are above well above the threshold for phytotoxicity limit. Lastly, the hydrogels also showed potential as a growing substrate in soilless cultivation.

Screening of Blackgram Genotypes for Drought Tolerance using PEG (Polyethylene Glycol) Induced Drought Stress at Seedling Stage

Background: Drought is one of the abiotic factor. It is considered to be a moderate loss of water. Water is main source involving for all activities of plant growth throughout the crop plants. Seed germination is considered as one of the first and foremost fundamental life stages of a plant, where the success in growth and yield is also depending on this stage. Methods: An experiment was conducted in order to study the effect of different concentrations (i.e., 0, 10, 20 and 30%) of polyethylene glycol (PEG) stress on germination and early growth stages of 28 genotypes of black gram. Different germination indices such as germination percent, radical length, plumule length, along with drought parameters like drought tolerance index was measured. Conclusion: Results showed significant differences among the cultivars at each drought stress level and significant decrease was observed in germination, length of radical and plumule and radical and plumule dry matter parameters, among all the genotypes genotypes Nirmal 7, NRIB 002, MDU 1, VBN 8 and NUL 7 VISWAS showed their efficiency in terms of germination and germination attributes to with stand to the drought conditions.