Seed Germination Responses to Temperature and Osmotic Stress Conditions in Brachiaria Forage Grasses
by
, , and
Francuois L. Müller
1,*, 
Jabulile E. Leroko
2,
Clement F. Cupido
1,
Igshaan Samuels
1,2
,
Nothando Ngcobo
1,
Elizabeth L. Masemola
1,
Fortune Manganyi-Valoyi
1 and
Tlou Julius Tjelele
1,3 1
Agricultural Research Council—Animal Production: Rangeland and Forage Sciences, Private Bag X2, Irene, Pretoria 0062, South Africa
2
Department of Biodiversity and Conservation Biology, University of the Western Cape, Private Bag X17, Bellville, Cape Town 7535, South Africa
3
Department of Agriculture and Animal Health, College of Agriculture and Environmental Sciences, University of South Africa, Florida Campus, Roodepoort 1709, South Africa
*
Author to whom correspondence should be addressed.
Grasses 2024, 3(4), 264-273; https://doi.org/10.3390/grasses3040019
Submission received: 16 September 2024
/
Revised: 10 October 2024
/
Accepted: 14 October 2024
/
Published: 17 October 2024
Abstract
:Brachiaria forages are known to be drought-tolerant as mature plants, but no information about drought tolerance at the seed germination stage is currently available. This study aimed to determine the impacts of different temperature and moisture conditions on the seed germination characteristics of five Brachiaria genotypes. Brachiaria seeds were germinated under constant temperatures of 5 °C–45 °C at increments of 5 °C. Within each temperature treatment, five osmotic treatments (0 MPa, −0.1 MPa, −0.3 MPa, −0.5 MPa, and −0.7 MPa) were applied, and germination was recorded daily for 20 days. The results showed that seed germination in all Brachiaria species was significantly negatively impacted (p < 0.05) by osmotic stress as well as by high and low temperatures. For all species, germination only occurred between 15 and 40 °C. Under optimum moisture conditions (0 MPa), the optimum germination temperatures for B. humidicola were 15 to 35 °C, for B. brizantha and B. nigropedata, they were 15 to 20 °C, for B. decumbens, they were 15 to 25 °C, and for the hybrid Brachiaria species, the optimum germination temperature was only 20 °C. In all species, seed germination decreased as moisture conditions became more limiting. Only B. humidicola germinated optimally at a high temperature (35 °C). At these temperatures, the species had more than 82% germination when moisture was not a limiting factor (0 MPa), but at low osmotic stress conditions (−0.1 MPa) at 30 °C, the germination of this species decreased to 67%. In conclusion, the results from this study indicate that the seed germination and early seedling establishment stages of Brachiaria grasses are only moderately tolerant to drought stress. Further work on early seedling responses to temperature and moisture stresses is needed to quantify early seedling responses to these stresses and to develop more detailed planting time guidelines for farmers.
1. Introduction
Climate change can either directly or indirectly impact livestock production. One of the key indirect impacts of climate change on livestock production is the effects of elevated temperatures and reduced water availability on forage production and quality [1,2,3]. This has motivated the world to look for forages that are adapted to extreme bioclimatic conditions and at the same time have the ability to potentially reduce greenhouse gas emissions from livestock production systems [1,4]. Brachiaria grass, a genus of the subfamily Panicoideae, is known for its high biomass production and forage quality and has been identified as a suitable candidate for production under adverse bioclimatic conditions [5,6,7]. There are more than 100 documented species in the genus Brachiaria [8,9], all of which naturally occur in the tropical and subtropical regions of Africa [10]. Seven Brachiaria species, i.e., B. decumbens, B. humidicola, B. brizantha, B. mutica, B. arrecta, B. ruziziensis, and B. dictyoneura are used as commercial forages [8,11]. Furthermore, crosses between B. ruziziensis, B. decumbens, and B. brizantha have resulted in several hybrid species being produced with increased resistance to pests and diseases, higher palatability, and improved nutritional quality [10].
Although cultivars of these commercial Brachiaria species and hybrids have been performing well in the Americas, especially Brazil, only small areas have been sown in Africa, despite many of the species naturally occurring on the continent [10]. Recently improved cultivars of B. brizantha, B. humidicola, B. decumbens, and B. nigropedata, and hybrid Brachiaria cultivars (B. brizantha × decumbens × ruziziensis) have been released in South Africa as pasture grasses. Brachiaria humidicola and B. nigropedata are considered grazing pastures, while B. brizantha, B. decumbens, and the hybrid cultivars are suitable for grazing, hay, and silage production. However, similar to other African countries, the adoption of these forages has been poor. This may be partially due to difficulties in seed germination and seedling establishment.
It is well known that the establishment of productive pastures depends on rapid and uniform seed germination and seedling establishment [12,13,14]. Furthermore, the success with which pasture seeds are able to germinate and establish is closely related to the favorability of their surrounding environmental conditions, and is controlled by many environmental factors, among which temperature and moisture conditions strongly regulate germination dynamics [14,15]. Under rainfed farming conditions, moisture stress is one of the most important factors preventing seeds from germinating [15]. For germination to commence after the release of dormancy, seeds must imbibe water from the soil [15,16,17]. Soil water potential can influence seed germination either directly through changes in water content and hydraulic conductivity in the soil or indirectly through physiological processes that occur during imbibition and seed germination [17,18]. In most seeds, germination takes place only when a critical moisture level is attained in the seed. However, the base water potential that is required for germination has been found to vary greatly among species, but it is closely related to the environmental conditions in which the species naturally occur, or in the case of improved pastures, the conditions that the cultivars were developed for [19,20].
In summer rainfall areas, the adverse effects of moisture stress on seed germination may be further aggravated by the exposure of seeds to temperatures that are above the optimum [21,22]. Temperature is the major determinant of germination rate once seed dormancy has been released, and therefore it impacts the rate of pasture establishment [20,23,24]. This, in turn, impacts the survival of the established seedlings. For planted pastures cultivated under rainfed conditions, optimum soil moisture conditions are usually only available for short periods, after which high temperatures rapidly dry the soil. Therefore, seeds need to germinate and establish rapidly while soil moisture is sufficient. Without sufficient soil moisture at germination to facilitate seed germination and initial seedling establishment, and without follow-up rains, seedling desiccation can be expected, which, in turn, significantly reduces pasture establishment and the planned forage yield [25,26].
Although Brachiaria grasses are known to be drought-tolerant as mature plants [6,27], no information about drought tolerance at the seed germination stage is currently available. Therefore, this study aimed to determine the impacts of different temperature and moisture conditions on the seed germination dynamics of Brachiaria humidicola, Brachiaria brizantha, Brachiaria decumbens, Brachiaria nigropedata, and a hybrid Brachiaria species, (B. brizantha × B. decumbens × B. ruziziensis). We hypothesized that although optimum germination temperatures and osmotic conditions would differ between the species, all of the species would be able to germinate under severe moisture and temperature stress conditions.
2. Materials and Methods
2.1. Brachiaria Seeds and Initial Seed Germination Potential Determination
Seeds of Brachiaria humidicola (cv. Llanero), Brachiaria brizantha (cv. Marandu), B. nigropedata (cv. Nigropedata), B. decumbens (cv. Basilisk), and the hybrid Brachiaria species, B. brizantha × B. decumbens × B. ruziziensis (cv. Mulato II) were obtained from commercial seed distributors (Barenbrug seeds and Brasuda) in South Africa as well as from the South African National Forage genebank. The seeds were tested for their initial germination potential by germinating in the dark four replicates of 100 seeds of each cultivar in 9 cm petri dishes on filter paper in a germination chamber set at a constant temperature of 20 °C. The seeds were watered as needed, and germination was recorded daily for 15 days. Seeds were regarded as germinated after the emergence of a radicle greater than 0.5 cm. All species had an initial germination potential below 90%, which resulted in all subsequent germination obtained in the subsequent seed germination experiments being calculated as a percentage of the initial germination. This was done following equation 1.
Equation 1: % = (xn/xi) × 100: where % is the final germination percentage expressed as a percentage of the initial germination potential of the species, Xn is the germination percentage obtained under the different experimental treatments, and Xi is the initial germination percentage.
2.2. Seed Germination Trial at Different Temperature and Osmotic Treatments
After the initial germination potential determination, four replicates of 100 seeds for each temperature and osmotic treatment combination within a species were placed in 9 cm petri dishes on a layer of filter paper. The germination chambers were calibrated to constant temperatures of 5 °C–45 °C at increments of 5 °C under continuous dark conditions. Within each temperature treatment, five osmotic treatments (0 MPa, −0.1 MPa, −0.3 MPa, −0.5 MPa, and −0.7 MPa) were imposed on the seeds. The osmotic treatments were prepared using polyethylene glycol 6000 (PEG6000) in accordance with the methods established by Michael and Kaufmann [28]. The osmotic solutions were stored in the germination chambers at each of the associated temperature treatments. A total of 5 mL of each osmotic solution was added to the petri dishes, and distilled water was used as the 0 MPa or control treatment. After watering, the petri dishes were sealed using parafilm to prevent excessive water loss. The filter paper and osmotic solutions were replaced every four days in order to keep osmotic conditions within the petri dishes relatively constant. Seed germination was recorded daily for 20 days, and germinated seeds were removed from the petri dishes as required to minimize excessive uptake of available water resources by the germinated seeds.
2.3. Statistical Analyses
All data were statistically analyzed using IBM SPSS for Windows Version 22.0 (IBM Corporation 2013, Armonk, NY, USA). All data were tested for normality using the Shapiro–Wilk test, after which the data were analyzed using a one-way analysis of variance (ANOVA) with Fisher’s Least Significant Difference (LSD) post hoc test to determine whether significant differences (p ≥ 0.05) were obtained between the temperature and osmotic treatments within each species.
3. Results
The initial germination potentials of the species that were obtained were 89%, 80%, 85%, 81%, and 72% for B. humidicola, B. brizantha, B. decumbens, B. nigropedata, and the hybrid Brachiaria, respectively. Therefore, all further results discussed are expressed as a percentage of this initial seed germination potential. The results from the experiments indicated that seed germination in all Brachiaria species evaluated were negatively impacted by osmotic stress conditions as well as by low and high temperatures. For all species evaluated, germination only occurred between 15 and 40 °C, with no seed germination at 5 °C, 10 °C, and 45 °C.
3.1. Brachiaria Humidicola Seed Germination
Under optimum moisture conditions, B. humidicola had an optimum germination temperature range of between 15 °C and 35 °C. However, as water limitation became more severe, the optimum germination temperature range changed to between 15 °C and 25 °C at −0.1 MPa, to between 20 °C and 25 °C at −0.3 MPa, and to 20 °C at −0.5 and −0.7 MPa (Table 1). Generally, no differences (p ≥ 0.05) were observed in seed germination under optimum moisture (0 MPa) conditions and low moisture stress (−0.1 MPa) conditions between 15 °C and 25 °C, but seed germination decreased significantly (p < 0.05) at 30 °C (Table 1). Within this 15 °C–25 °C temperature range, at 15 °C and 20 °C, B. humidicola seed germination further decreased significantly (p < 0.05) from low osmotic stress conditions (−0.1 MPa) to moderate osmotic stress conditions (−0.3 MPa), but did not differ significantly at 25 °C (Table 1). From moderate osmotic stress conditions, seed germination significantly decreased (p < 0.05) at severe osmotic stress conditions (−0.5 MPa and −0.7 MPa), irrespective of the germination temperature (Table 1).
3.2. Brachiaria Brizantha Seed Germination
Under optimum moisture conditions, B. brizantha had an optimum germination temperature range of between 15 °C and 20 °C (Table 2). As water limitation became more severe (−0.1 MPa and −0.3 MPa), the optimum germination temperature changed to between 20 °C and 25 °C (Table 2), even though 80% germination could only be achieved at 20 °C under optimum osmotic conditions. Unlike B. humidicola, B. brizantha could not tolerate even low (−0.1 MPa) moisture stress conditions, even at the optimum germination temperature of 20 °C. It was found that seed germination in B. brizantha significantly decreased (p ≥ 0.05) from 85% to 66% when water limitation decreased from 0 MPa to −0.1 MPa (Table 2).
3.3. Brachiaria Decumbens Seed Germination
Under optimum moisture conditions, B. decumbens had an optimum germination temperature range of between 15 °C and 25 °C (Table 3). As water limitation became more severe, the optimum germination temperature range changed to between 15 °C and 20 °C at −0.1 MPa to −0.7 MPa (Table 3). Generally, no differences (p ≥ 0.05) were observed in seed germination under optimum moisture (0 MPa) and low moisture stress (−0.1 MPa) conditions at 15 °C and 20 °C, but seed germination decreased significantly (p ≥ 0.05) at 25 °C (Table 3). Within the 15 °C–25 °C temperature range, seed germination decreased significantly (p < 0.05) from low osmotic stress conditions (−0.1 MPa) to moderate (−0.3 MPa) and severe (−0.5 MPa and −0.7 MPa) osmotic stress conditions, irrespective of the germination temperature (Table 3).
3.4. Brachiaria Nigropedata Seed Germination
B. nigropedata had an optimum germination temperature range of between 15 °C and 20 °C at optimum osmotic stress conditions (0 MPa) to moderate osmotic stress conditions (−0.3 MPa) (Table 4). However, seed germination reached 90% and 81% even at 25 °C under optimum (0 MPa) and low (−0.1 MPa) osmotic stress conditions, respectively. Generally, seed germination decreased significantly (p < 0.05) from optimum osmotic conditions (0 MPa) to low osmotic stress conditions (−0.1 MPa), and decreased even further as water limitation became more severe, irrespective of the germination temperature (Table 4).
3.5. Hybrid Brachiaria Seed Germination
The hybrid Brachiaria species (B. brizantha × B. decumbens × B. ruziziensis) had an optimum germination temperature of 20 °C, irrespective of the osmotic conditions under which the seeds were germinated (Table 5). Although seed germination exceeded 70% even under low osmotic stress conditions (−0.1 MPa) at 15 °C, seed germination decreased significantly (p < 0.05) from optimum osmotic conditions (0 MPa) to low osmotic stress conditions (−0.1 MPa), and significantly (p < 0.05) decreased further as the osmotic stress became more severe (Table 5).
3.6. Time to Germination in B. humidicola, B. brizantha, B. nigropedata, B. decumbens, and the Hybrid BRACHIARIA
When considering the impact of temperature and osmotic conditions on the time to germination (Table 6), it was clear that both temperature and osmotic conditions had a significant (p < 0.05) impact on the time to seed germination. Generally, seed germination was initiated faster at warmer temperatures, but as moisture became more limiting, time to germination increased, i.e., it became longer. Brachiaria humidicola, B. brizantha, and the Brachiaria hybrid were all very slow to initiate germination at 15 °C, even at optimum osmotic conditions. In all instances however, irrespective of the germination temperatures, as moisture limitation became more severe, the time to germination increased.
4. Discussion
This study evaluated the germination responses of five Brachiaria genotypes at different temperature and osmotic conditions. We hypothesized that the species would respond differently to temperature and osmotic stress conditions, but that all of the species would be able to germinate under severe moisture and temperature stress conditions. The results from the experiment indicated that all Brachiaria species evaluated had a wide temperature range under which they were able to germinate (15 °C–40 °C), even though the optimum germination temperature ranges differed between the species, which depended on water availability. Germination was, however, found to generally be lower at higher temperatures, and this was especially true as osmotic stress became more severe. These responses are likely associated with the enzyme activity and oxygen availability of seeds, which are known to decrease when germinated at unfavorable temperatures and under limiting moisture conditions [15]. Furthermore, higher incubation temperatures and increased moisture stress during germination likely induced secondary dormancy of seeds, leading to prolonged seed germination over non-optimal temperatures and increased osmotic stress [14].
Both temperature and osmotic stress conditions are known to impact seed germination [15]. High temperatures are known to damage seeds and stop seed germination from either commencing or completing [15,29,30], and even at the most favorable osmotic conditions, temperature can limit the capacity and rate of seed germination in most plants [31]. This was evident in the current study, where germination was lowest at higher temperatures (35 °C–40 °C), with no germination occurring at 45 °C for all species evaluated, even at optimum moisture availability. The fact that germination did not occur at 5 °C and 10 °C could be attributed to the natural conditions under which these species occur or to the conditions that the specific cultivars were bred for. Several studies have shown that the environmental and topographical conditions from where seeds are collected can significantly affect the germination rate and success of seeds at various combinations of osmotic stresses and temperatures [24,32,33]. All Brachiaria species evaluated have a tropical to subtropical distribution, where the rainfall and establishment season is in summer, and generally correspond to moderately warm conditions. This corresponds to the results indicating that optimum seed germination occurred at 20 °C (with some species having optimum ranges of 15 °C–25 °C), when more than 80% of the seeds germinated.
The results from this study also showed that the Brachiaria species evaluated did well under low osmotic stress conditions. Generally, seed germination decreased with an increase in osmotic stress, and this was found to be the case for all species evaluated. This was similar to the results of a study conducted by Bonvissuto and Busso [30] on several other perennial grass species. Among the many Brachiaria grasses used as pastures, the species evaluated in this trial are known to be drought-tolerant as mature plants [34,35]. In this study, however, it was clear that all of the species evaluated could only tolerate low levels of drought (osmotic) stress, with seed germination only exceeding 80% at osmotic potentials up to −0.1 MPa for most of the species. Brachiaria brizantha, however, was found to not tolerate drought well, as germination for this species only exceeded 80% under optimum osmotic conditions (0 MPa).
5. Conclusions
This study aimed to determine the impacts of different temperature and moisture conditions on the seed germination dynamics of B. humidicola, B. brizantha, B. decumbens, B. nigropedata, and a hybrid Brachiaria (B. brizantha × B. decumbens × B. ruziziensis). It was hypothesized that although optimum germination temperatures and osmotic conditions would differ between the species, all of the species evaluated would be able to germinate under severe moisture and temperature stress conditions. Contrary to this, however, our results showed that although the majority of the species evaluated were able to tolerate a wide germination temperature range, as soon as moisture became more limiting, none of the Brachiaria species could tolerate even moderate drought stress conditions at their germination stages. These results have implications for when these forages should be planted. Due to the fact that temperature stress was less limiting than moisture stress, it is suggested that these species be planted later in the summer months when rainfall is less variable and more regular, even if temperatures are higher. However, before such recommendations can be made, it is important to do further evaluations on early seedling responses to temperature and osmotic stress and quantify survival and growth responses to these stresses to develop more detailed planting time guidelines for farmers.
Author Contributions
F.L.M. and J.E.L.; investigation, J.E.L., N.N., E.L.M., and F.M.-V.; data curation, F.L.M.; writing—original draft preparation, J.E.L. and F.L.M.; writing—review and editing, I.S., C.F.C., and T.J.T.; visualization, F.L.M.; supervision, F.L.M., I.S., and C.F.C.; project administration, T.J.T.; funding acquisition, F.L.M. and T.J.T. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by the Water Research Commission of South Africa, C2020/2021-00398.
Data Availability Statement
All data presented in this manuscript are available from the corresponding author upon reasonable request.
Acknowledgments
The authors would like to thank the ARC-National Forage Genebank team for their assistance with establishing and maintaining the trials.
Conflicts of Interest
The authors declare no conflicts of interest.
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Table 1.
Seed germination in Brachiaria humidicola at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
Table 1.
Seed germination in Brachiaria humidicola at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
| Osmotic Treatment | Temperature (°C) | Significance | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | ||
| 0 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 86.8 ± 1.7 cC | 90.7 ± 1.6 bC | 81.2 ± 1.2 cC | 82.2 ± 3.7 dC | 82.0 ± 2.1 dC | 41.3 ± 5.5 dB | 0.0 ± 0.0 aA | F(8,36) = 226.8, p < 0.001 |
| −0.1 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 83.4 ± 7.3 cD | 85.7 ± 2.4 bD | 80.6 ± 2.1 cD | 67.9 ± 3.7 cC | 62.1± 3.4 cC | 23.0 ± 3.1 cB | 0.0 ± 0.0 aA | F(8,36) = 111.87, p < 0.001 |
| −0.3 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 53.4 ± 7.6 bC | 79.8 ± 0.8 aD | 73.3 ± 2.2 cD | 62.4 ± 4.9 cC | 14.1 ± 9.8 bB | 4.8 ± 2.4 bA | 0.0 ± 0.0 aA | F(8,36) = 56.76, p < 0.001 |
| −0.5 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 29.5 ± 2.5 aB | 75.0 ± 3.4 aD | 43.8 ± 2.1 bC | 25.3 ± 2.8 bB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 212.97, p < 0.001 |
| −0.7 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 12.4 ± 1.5 aB | 67.1 ± 4.7 aC | 15.2 ± 2.5 aB | 5.1 ± 2.1 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 123.2, p < 0.001 |
| Significance | - | - | F(4,20) = 43.71, p < 0.001 | F(4,20) = 9.85, p < 0.001 | F(4,20) = 195.75, p < 0.001 | F(4,20) = 51.26, p < 0.001 | F(4,20) = 64.4, p < 0.001 | F(4,20) = 36.14, p < 0.001 | - | |
Table 2.
Seed germination in Brachiaria brizantha at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
Table 2.
Seed germination in Brachiaria brizantha at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
| Osmotic Treatment | Temperature (°C) | Significance | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | ||
| 0 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 74.4 ± 4.9 dD | 85.3 ± 0.8 cD | 63.4 ± 4.8 cC | 65.3 ± 4.4 eC | 60.3 ± 2.9 dC | 1.9 ± 0.6 bB | 0.0 ± 0.0 aA | F(8,36) = 226.80, p < 0.001 |
| −0.1 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 49.4 ± 3.6 cD | 66.9 ± 3.6 bF | 60.3 ± 5.8 cEF | 50.9 ± 4.9 dE | 39.4 ± 5.1 cC | 1.9 ± 1.5 bB | 0.0 ± 0.0 aA | F(8,36) = 111.87, p < 0.001 |
| −0.3 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 27.8 ± 2.9 bBC | 59.7 ± 3.1 abD | 46.3 ± 4.6 bCD | 16.3 ± 4.2 cB | 7.2 ± 4.0 bA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 56.76, p < 0.001 |
| −0.5 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 10.6 ± 2.9 aB | 48.4 ± 3.1 abD | 17.5 ± 2.6 aC | 5.3 ± 1.1 bB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 212.97, p < 0.001 |
| −0.7 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 2.5 ± 1.1 aA | 26.3 ± 3.6 aB | 1.9 ± 0.6 aA | 2.8 ± 1.1 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 123.00, p < 0.001 |
| Significance | - | - | F(4,20) = 43.71, p < 0.001 | F(4,20) = 9.85, p < 0.001 | F(4,20) = 195.75, p < 0.001 | F(4,20) = 51.26, p < 0.001 | F(4,20) = 64.40, p < 0.001 | F(4,20) = 36.1, p < 0.001 | - | |
Table 3.
Seed germination in Brachiaria decumbens at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
Table 3.
Seed germination in Brachiaria decumbens at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
| Osmotic Treatment | Temperature (°C) | Significance | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | ||
| 0 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 90.9 ± 0.3 dE | 91.5 ± 3.5 dE | 90.2 ± 0.7 eE | 65.3 ± 0.6 eD | 37.4 ± 1.6 cC | 10.6 ± 0.8 cB | 0.0 ± 0.0 aA | F(8,36) = 961.99, p < 0.001 |
| −0.1 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 85.0 ± 0.6 dE | 84.4 ± 1.9 dE | 77.1 ± 1.0 dD | 49.1 ± 1.0 dC | 13.5 ± 1.7 bB | 2.9 ± 0.6 bA | 0.0 ± 0.0 aA | F(8,36) = 1449.27, p < 0.001 |
| −0.3 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 71.2 ± 0.3 cE | 71.8 ± 0.5 cE | 52.6 ± 1.7 cD | 19.4 ± 1.6 cC | 3.8 ± 0.3 aB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 1587.99, p < 0.001 |
| −0.5 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 46.2 ± 1.3 bD | 41.2 ± 1.3 bD | 14.7 ± 1.0 bC | 9.7 ± 0.6 bB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 662.37, p < 0.001 |
| −0.7 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 6.5 ± 1.1 aC | 7.6 ± 0.6 aC | 3.8 ± 0.6 aB | 4.1 ± 0.3 aB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 42.78, p < 0.001 |
| Significance | - | - | F(4,20) = 1705, p < 0.001 | F(4,20) = 333.6, p < 0.001 | F(4,20) = 1232, p < 0.001 | F(4,20) = 832.5, p < 0.001 | F(4,20) = 22.19, p < 0.001 | F(4,20) =101.33, p < 0.001 | - | |
Table 4.
Seed germination in Brachiaria nigropedata at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
Table 4.
Seed germination in Brachiaria nigropedata at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
| Osmotic Treatment | Temperature (°C) | Significance | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | ||
| 0 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 96.9 ± 1.3 eE | 95.1 ± 0.5 eE | 90.7 ± 0.61 eD | 75.0 ± 1.1 eC | 37.7 ± 0.8 eB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 4557.6, p < 0.001 |
| −0.1 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 87.0 ± 0.6 dF | 84.3 ± 1.1 dE | 81.5 ± 0.5 dD | 54.9 ± 0.6 dC | 30.2 ± 0.4 dB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 6265.7, p < 0.001 |
| −0.3 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 71.9 ± 0.8 cE | 71.0 ± 0.8 cE | 60.5 ± 0.5 cD | 21.0 ± 1.3 cC | 14.8 ± 0.5 cB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 2608.7, p < 0.001 |
| −0.5 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 43.2 ± 1.3 bD | 43.8 ± 2.3 bD | 24.7 ± 1.1 bC | 4.3 ± 0.4 bB | 10.2 ± 0.8 bB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 344.2, p < 0.001 |
| −0.7 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 9.9 ± 0.9 aB | 9.3 ± 0.4 aB | 6.5 ± 0.3 aB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 174.1, p < 0.001 |
| Significance | - | - | F(4,20) = 1210.9, p < 0.001 | F(4,20) = 813.2, p < 0.001 | F(4,20) = 2914.5, p < 0.001 | F(4,20) = 1575, p < 0.001 | F(4,20) = 717.1, p < 0.001 | - | - | |
Table 5.
Seed germination in the Brachiaria hybrid (B. brizantha × B. decumbens × B. ruziziensis) at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
Table 5.
Seed germination in the Brachiaria hybrid (B. brizantha × B. decumbens × B. ruziziensis) at different temperature and osmotic treatments. Statistically significant differences (p < 0.05) in seed germination between different osmotic treatments within each temperature are indicated by different lowercase letters, while statistically significant differences between temperature treatments within each osmotic treatment are indicated by different superscript uppercase letters.
| Osmotic Treatment | Temperature (°C) | Significance | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | ||
| 0 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 75.3 ± 1.8 cD | 91.0 ± 1.8 dE | 77.1 ± 1.7 eD | 32.6 ± 1.7 dC | 21.5 ± 4.3 bB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 429.55, p < 0.001 |
| −0.1 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 71.5 ± 3.8 cCD | 84.0 ± 7.0 cD | 62.5 ± 1.0 dC | 17.4 ± 0.7 cB | 16.0 ± 2.3 bB | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 153.68, p < 0.001 |
| −0.3 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 30.9 ± 6.1 bB | 69.4 ± 4.0 bC | 35.8 ± 2.3 cB | 6.9 ± 1.0 bA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 92.50, p < 0.001 |
| −0.5 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 3.1 ± 0.7 aA | 24.0 ± 3.7 aC | 11.5 ± 0.3 bB | 2.8 ± 0.6 abA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 41.34, p < 0.001 |
| −0.7 MPa | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 3.5 ± 0.4 aA | 16.3 ± 2.6 aB | 1.7 ± 0.3 aA | 1.7 ± 0.3 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | 0.0 ± 0.0 aA | F(8,36) = 34.69, p < 0.001 |
| Significance | - | - | F(4,20) = 112.95, p < 0.001 | F(4,20) = 67.24, p < 0.001 | F(4,20) = 563.93, p < 0.001 | F(4,20) = 181.28, p < 0.001 | F(4,20) = 23.29, p < 0.001 | - | - | |
Table 6.
Time to first seed germination in five Brachiaria species under different temperature and osmotic treatments.
Table 6.
Time to first seed germination in five Brachiaria species under different temperature and osmotic treatments.
| Osmotic Treatment | Temperature (°C) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | ||
| B. humidicola | 0 MPa | - ± - | - ± - | 10.0 ± 0.0 | 4.0 ± 0.0 | 3.0 ± 0.0 | 3.0 ± 0.0 | 2.0 ± 0.0 | 2.0 ± 0.0 | - ± - |
| −0.1 MPa | - ± - | - ± - | 10.3 ± 0.3 | 4.3 ± 0.3 | 3.0 ± 0.0 | 3.0 ± 0.0 | 2.3 ± 0.3 | 2.0 ± 0.0 | - ± - | |
| −0.3 MPa | - ± - | - ± - | 12.0 ± 0.7 | 4.3± 0.3 | 3.0 ± 0.0 | 3.0 ± 0.0 | 5.0 ± 0.0 | 5.3 ± 0.7 | - ± - | |
| −0.5 MPa | - ± - | - ± - | 12.5 ± 0.3 | 4.3 ± 0.3 | 3.0 ± 0.0 | 3.0 ± 0.0 | - ± - | - ± - | - ± - | |
| −0.7 MPa | - ± - | - ± - | 13.0 ± 0.0 | 4.5 ± 0.3 | 4.0 ± 0.7 | 5.5 ± 1.2 | - ± - | - ± - | - ± - | |
| B. brizantha | 0 MPa | - ± - | - ± - | 10.8 ± 0.3 | 5.0 ± 0.4 | 3.0 ± 0.0 | 3.0 ± 0.0 | 2.0 ± 0.0 | 9.0 ± 0.0 | - ± - |
| −0.1 MPa | - ± - | - ± - | 11.8 ± 0.5 | 4.3 ± 0.3 | 3.0 ± 0.0 | 3.0 ± 0.0 | 2.0 ± 0.0 | 9.5 ± 0.5 | - ± - | |
| −0.3 MPa | - ± - | - ± - | 11.8 ± 0.5 | 4.5 ± 0.5 | 3.3 ± 0.3 | 3.8 ± 0.5 | 5.0 ± 2.5 | - ± - | - ± - | |
| −0.5 MPa | - ± - | - ± - | 14.0 ± 1.7 | 5.0 ± 1.0 | 3.0 ± 0.0 | 4.0 ± 0.4 | - ± - | - ± - | - ± - | |
| −0.7 MPa | - ± - | - ± - | 18.3 ± 1.7 | 6.3 ± 1.3 | 6.3 ± 0.0 | 4.0 ± 0.6 | - ± - | - ± - | - ± - | |
| B. decumbens | 0 MPa | - ± - | - ± - | 4.0 ± 0.0 | 3.0 ± 0.0 | 3.0 ± 0.0 | 3.0 ± 0.0 | 5.0 ± 0.0 | - ± - | - ± - |
| −0.1 MPa | - ± - | - ± - | 5.0 ± 0.0 | 4.3 ± 0.3 | 4.0 ± 0.0 | 3.0 ± 0.0 | 9.0 ± 0.0 | - ± - | - ± - | |
| −0.3 MPa | - ± - | - ± - | 6.0 ± 0.0 | 4.5 ± 0.5 | 6.0 ± 0.0 | 4.0 ± 0.0 | 11.0 ± 0.0 | - ± - | - ± - | |
| −0.5 MPa | - ± - | - ± - | 8.0 ± 0.0 | 5.0 ± 1.0 | 12.0 ± 0.0 | 11.0 ± 0.0 | - ± - | - ± - | - ± - | |
| −0.7 MPa | - ± - | - ± - | 15.0 ± 0.0 | 6.8 ± 1.6 | 13.3 ± 0.3 | 12.0 ± 0.0 | - ± - | - ± - | - ± - | |
| B. nigropedata | 0 MPa | - ± - | - ± - | 4.0 ± 0.0 | 4.0 ± 0.0 | 3.0 ± 0.0 | 3.0 ± 0.0 | 3.0 ± 0.0 | - ± - | - ± - |
| −0.1 MPa | - ± - | - ± - | 5.0 ± 0.0 | 4.0 ± 0.0 | 3.0 ± 0.0 | 4.0 ± 0.0 | 5.0 ± 0.0 | - ± - | - ± - | |
| −0.3 MPa | - ± - | - ± - | 9.0 ± 0.0 | 6.0 ± 0.0 | 5.0 ± 0.0 | 6.0 ± 0.0 | 10.0 ± 0.0 | - ± - | - ± - | |
| −0.5 MPa | - ± - | - ± - | 11.0 ± 0.0 | 9.0 ± 0.0 | 7.0 ± 0.0 | 1.0 ± 0.0 | 11.0 ± 0.0 | - ± - | - ± - | |
| −0.7 MPa | - ± - | - ± - | 15.0 ± 0.0 | 12.0 ± 0.0 | 9.0 ± 0.0 | - ± - | - ± - | - ± - | - ± - | |
| B. hybrid | 0 MPa | - ± - | - ± - | 12.0 ± 0.6 | 6.3 ± 0.3 | 4.5 ± 0.5 | 3.0 ± 0.0 | 2.0 ± 0.0 | - ± - | - ± - |
| −0.1 MPa | - ± - | - ± - | 11.5 ± 0.5 | 6.0 ± 0.4 | 4.5 ± 0.9 | 3.0 ± 0.0 | 3.0 ± 0.0 | - ± - | - ± - | |
| −0.3 MPa | - ± - | - ± - | 13.5 ± 0.5 | 6.5 ± 0.6 | 8.0 ± 0.6 | 3.3 ± 0.3 | - ± - | - ± - | - ± - | |
| −0.5 MPa | - ± - | - ± - | 14.0 ± 0.0 | 9.0 ± 1.2 | 11.3 ± 0.3 | 5.8 ± 1.1 | - ± - | - ± - | - ± - | |
| −0.7 MPa | - ± - | - ± - | 15.0 ± 0.0 | 8.5 ± 1.3 | 13.3 ± 0.3 | 4.3 ± 0.3 | - ± - | - ± - | - ± - | |
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MDPI and ACS Style
Müller, F.L.; Leroko, J.E.; Cupido, C.F.; Samuels, I.; Ngcobo, N.; Masemola, E.L.; Manganyi-Valoyi, F.; Tjelele, T.J. Seed Germination Responses to Temperature and Osmotic Stress Conditions in Brachiaria Forage Grasses. Grasses 2024, 3, 264-273. https://doi.org/10.3390/grasses3040019
AMA Style
Müller FL, Leroko JE, Cupido CF, Samuels I, Ngcobo N, Masemola EL, Manganyi-Valoyi F, Tjelele TJ. Seed Germination Responses to Temperature and Osmotic Stress Conditions in Brachiaria Forage Grasses. Grasses. 2024; 3(4):264-273. https://doi.org/10.3390/grasses3040019
Chicago/Turabian StyleMüller, Francuois L., Jabulile E. Leroko, Clement F. Cupido, Igshaan Samuels, Nothando Ngcobo, Elizabeth L. Masemola, Fortune Manganyi-Valoyi, and Tlou Julius Tjelele. 2024. "Seed Germination Responses to Temperature and Osmotic Stress Conditions in Brachiaria Forage Grasses" Grasses 3, no. 4: 264-273. https://doi.org/10.3390/grasses3040019
APA StyleMüller, F. L., Leroko, J. E., Cupido, C. F., Samuels, I., Ngcobo, N., Masemola, E. L., Manganyi-Valoyi, F., & Tjelele, T. J. (2024). Seed Germination Responses to Temperature and Osmotic Stress Conditions in Brachiaria Forage Grasses. Grasses, 3(4), 264-273. https://doi.org/10.3390/grasses3040019
