Effect of temperature and water stress on germination characteristics and determination of cardinal temperatures of invasive weed Geranium robertianum

Document Type : Research Article

Authors

1 Ph.D Student Ferdowsi University of Mashhad

2 Ferdowsi University of Mashhad

3 Khorasan Razavi Agricultural Jihad Organization

10.22067/jpp.2023.78579.1103

Abstract

Introduction:Germination is the first and most important stage of establishment and subsequent successful competition, which is influenced by genetic and environmental factors. Soil water temperature and potential are the most important environmental factors. Getting knowledge of environmental factors controlling germination makes it possible to predict weed density. By obtaining information on the temperature and humidity needs of weeds, we can successfully manage them.

In recent years, Geranium robertianum weed in Mazandaran and Golestan provinces has been introduced as an invasive weed in rapeseed farms. Various models such as dent-like, segmented, and beta have been used to investigate the relationship between temperature and germination rate. The aim of this study was to determine the cardinal temperatures of Geranium robertianum and to investigate the role of temperature and water stress on some of its germination characteristics.

Materials and Methods: In order to investigate the effect of temperature and water stress on seed germination of Geranium robertianum weed, the present experiment was carried out. This experiment is a factorial experiment in a completely randomized design with 7 constant temperature levels (5, 10, 15, 20, 25, 30, 35, 40 ° C) and water stress at 6 levels (0, -0.2, 4). -0.4, -0.6, -0.8, -1) were performed in 4 replications. Germinated seeds were counted up to 14 days after germination. Then indices such as percentage, germination rate and time to reach 50% germination were calculated. A dent-like regression model was used to determine the cardinal temperature.

Results: The results showed that a constant temperature of 20 ° C has the highest percentage (98%) and germination rate (6.019) in non-water stress conditions (zero osmotic potential). Germination also stopped at 35 and 40 ° C. The three-parameter regression model had good accuracy to describe the trend of cumulative geranium germination percentage. The results also showed that with increasing osmotic stress, germination percentage and rate decreased and at potentials higher than -0.8 MPa, germination stopped. At zero potential (non-water stress conditions) the minimum, first optimum , second optimum, and ceiling temperatures were determined as 1.12, 18.83, 22.76 and 35.09 ° C, respectively. By increasing osmotic potential from zero to -0.8 MPa, minimum temperature from 1.12 to 4.96, optimal temperatures from 18.83 to 22.76 to 101.51 to 20.63 and ceiling temperature changed from 35.09 to 34.48 ° C. Therefore, in general, water stress has a greater effect on the minimum and optimal temperature of wild geranium germination. The general analysis of the results shows that up to medium potentials (-0.6 MPa) the highest germination rate is in the temperature range of 17 to 22 ° C and in the highest potential (-0.8 MPa) in the temperature range of 10 to 20 ° C. Celsius occurred.

Conclusion: According to the results of this study, the highest percentage and germination rate occurred at 20 ° C. There was no germination at temperatures of 35 and 40 ° C and also, an osmotic potential of 1 MPa. As the osmotic potential increased, the minimum temperature increased, the optimum temperatures decreased and the maximum temperature decreased slightly. In general, due to the low minimum temperature, the probability of germination and inundation of this weed in colder seasons will be higher. Therefore, in conclusion, due to the decrease in germination and the increase in the minimum germination temperature under osmotic stresses, the percentage and rate of wild geranium germination can be reduced with the first stresses of the season. Of course, it is worth noting that cultivars of drought tolerant crops should be used.Conclusion: According to the results of this study, the highest percentage and germination rate occurred at 20 ° C. There was no germination at temperatures of 35 and 40 ° C and also, an osmotic potential of 1 MPa. As the osmotic potential increased, the minimum temperature increased, the optimum temperatures decreased and the maximum temperature decreased slightly. In general, due to the low minimum temperature, the probability of germination and inundation of this weed in colder seasons will be higher. Therefore, in conclusion, due to the decrease in germination and the increase in the minimum germination temperature under osmotic stresses, the percentage and rate of wild geranium germination can be reduced with the first stresses of the season. Of course, it is worth noting that cultivars of drought tolerant crops should be used.

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