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Article

Seed Longevity in Desert Species and the Possibility of Forming a Persistent Soil Seed Bank

by
Majda K. Suleiman
,
Arvind Bhatt
*,
Sheena Jacob
,
Rini R. Thomas
and
Mini T. Sivadasan
Desert Agriculture and Ecosystems Program, Environment and Life Sciences Research Center, Kuwait Institute for Scientific Research, P.O. Box 24885, Safat 13109, Kuwait
*
Author to whom correspondence should be addressed.
Sustainability 2023, 15(22), 15904; https://doi.org/10.3390/su152215904
Submission received: 17 July 2023 / Revised: 29 August 2023 / Accepted: 31 August 2023 / Published: 14 November 2023
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Abstract

:
The formation of soil seed banks could be an important survival strategy for desert plant species that determine their persistence under harsh conditions, where temperature is extremely high, and chances of rainfall are low and unpredictable. Therefore, the assessment of the seed viability and germination potential of in-situ stored seeds could be important for understanding their reproductive strategies. Seeds of the studied species were collected in 2017 and divided into two batches. The first batch (fresh seeds) of each species was tested for seed germination within one week after collection. However, the second batch (in-situ stored seeds) was tested for seed germination in the first week of October 2022. In the current study, the germination potential of in-situ stored seeds was investigated in order to determine their ability to remain viable under natural conditions. Stored seeds of studied species showed higher germination percentages (53–89%) than fresh seeds (3–34%), except for Peganum harmala, indicating the presence of seed dormancy at the time of seed maturation. Seed germination percentages of all the species were significantly enhanced by storage, indicating their ability to form persistent soil seed banks, although the extent was species-specific. Fresh seeds of all the species attained higher germination in light as compared to complete darkness, suggesting that the germination of seeds can be restricted if they are buried deep in the soil under natural conditions. However, depending on species, in-situ seed storage changed the light requirement for germination. Additionally, the absence of an increase in the ratio of dead seeds between fresh and stored seeds indicates their ability to remain persistent in a soil seed bank and thus may offer great potential for maintaining and restoring desert ecosystems.

1. Introduction

Integration of both ex-situ and in-situ conservation methods are essential for conserving plant biodiversity. Ex-situ storage of seeds in a seed bank is considered to be one of the most cost-effective methods for conserving plant diversity and also offers a vital source of material for restoration [1]. In-situ stored seeds in a soil seed bank is considered to be a key factor for ecosystem restoration because these seeds have the potential to replace the adult plants [2,3]. Therefore, the soil seed bank is considered as a biodiversity reservoir and plays an important role in (i) species recruitment and establishment, (ii) long term conservation of genetic variation, (iii) determining the spatio-temporal distribution of species, and (iv) having direct implications for restoration and effective ecosystem management [1,4,5,6,7,8]. Moreover, seed persistence in a soil seed bank also contributes to determining the fate of plant populations and thus plays an important role in determining species survival and plant diversity [9,10,11]. Therefore, understanding the seed longevity in a soil seed bank could be crucial for predicting species distribution under changing climatic conditions as well as understanding the community dynamics in both short- and long-term perspectives [12,13]. In-situ storage of seeds can provide more accurate information on the viability loss and germinability over time because these seeds remain exposed to natural environmental conditions.
In arid deserts, plants are subjected to extremely high temperatures, high evaporation rates, low water availability, high salinity, and acute nutrient deficiencies [14,15]. All these factors contribute to creating this region as one of the most hostile places for plant growth and development. Maintaining soil seed banks in desert environmental conditions could be the adaptation strategy that enhances their chances of establishment under such unpredictable extreme weather conditions [16,17]. Usually, both dormant and non-dormant seeds are present in soil seed banks and consequently increases the chances of species persistence by synchronizing the germination timing with favorable seasons or in the absence of enough seed production during a particular year [17,18,19]. Since seed production in the desert is usually inconsistent and low due to scanty and irregular rainfall events [20,21], understanding the ability of desert species to form a soil seed bank could be important for designing restoration and conservation plans. Here the natural vegetation has been already degraded as a result of several factors such as overgrazing, off-road driving, and camping [22].
In a soil seed bank, seeds may either remain on the soil surface, partially buried, or completely buried, depending on the size and amount of litter cover [23]. Moreover, different species may exhibit differences in seed longevity in a soil seed bank. Seed banks have been categorized into three categories: (i) transient (<1 year), (ii) short-term persistent (1–5 years), and (iii) persistent (>5 years), based on their ability to remain viable in the soil [24]. Various factors such as temperature, light, moisture, soil properties, predation, and burial depth affect the seed persistence ability [25,26]. Therefore, understanding the seed longevity during storage is of prime concern and could be important for implementing suitable conservation and management strategies.
Understanding the factors influencing the viability of seeds in a soil seed bank could be useful for developing restoration strategies for desert habitats. However, the precise documentation of time duration for seed longevity in soil seed banks could be important for determining the success of restoration efforts. Seed longevity determines the period in which seeds can germinate and produce new individuals and consequently regulates the spatio-temporal dynamics of plant populations [27]. However, the ability to remain viable during desiccation is one of the most important aspects that affects seed longevity [28]. Most of the species that occur in arid hot regions produce orthodox seeds (i.e., desiccation tolerant) and have the ability to form soil seed banks [29,30]. Until now, few seed longevity studies have been conducted for ex-situ [31,32] and in-situ stored seeds [17,33]. Therefore, attention needs to be given to understanding how seed longevity is affected under natural conditions. Identifying the seed bank longevity by detecting the seed viability (i.e., germinability) could be crucial for implementing natural restoration measures. However, despite their importance for restoration, little is known about the potential of soil seed bank formation as well as seed longevity under natural conditions for Arabian desert species. We hypothesize that the seeds of desert species may have sufficient longevity to form persistent soil seed banks and therefore they can increase restoration potential by serving as a direct source of natural restoration. Hence, we compared the seed germination potential of fresh and in-situ stored seeds to address the following questions: (i) Do fresh and stored seeds have the same ability to germinate, (ii) whether seeds can maintain their viability and germination capacity under in-situ storage, and (iii) if yes, are there any differences in seed longevity among species?

2. Materials and Methods

2.1. Seed Collection

We collected seeds of 6 species [3 annuals (Centaurea pseudosinaica, Gypsophila capillaris, Lotus halophilus) and 3 perennials (Astragalus spinosus, Peganum harmala, Panicum turgidum)] from naturally occurring populations at the time of their dispersal (during May–June 2017). These species are relatively common and have both ecological and economic importance (Table 1, Figure 1 and Figure 2). Approximately 30–35 plants of each species were randomly sampled to represent the genetic diversity of respective populations. Fresh seed mass for each species was determined at the time of collection from 50 seeds, replicated four times, using an electronic balance (Sartorius Co., Goettingen, Germany). Seed color and seed shape were recorded using a Stereo Microscope (Nikon SMZ800N; Nikon Instruments Inc., Melville, NY, USA). The seeds were cleaned immediately after collection using a hand-made rubber thresher and care was taken not to scarify the seed coating while cleaning the seeds. After cleaning, seeds were divided into two batches: batch 1 as fresh seeds and batch 2 as stored seeds.
The first batch (fresh seeds) of each species was tested for seed germination within one week after collection. The second batch was stored (in situ) in a nylon bag (mesh size 0.2 mm) and placed outside in the soil at a depth of 2–4 cm from May–June 2017 to the last week of September 2022 (stored seeds). Whenever rain was forecasted, seeds of the natural storage (batch 2) were taken from the soil and were returned back shortly after improvement of the weather. The stored seeds of each species were retrieved by the first week of October 2022 and tested for germinability.
The Kuwait climate is characterized by a long, dry, and hot summer with daytime temperatures occasionally exceeding 50 °C, and cooler winters with extreme lows below 4 °C. Precipitation is scarce, with less than 114 mm annually and mostly occurring during winter between October and March [40].

2.2. Germination Trials

Seeds (both fresh and stored) of the selected species were germinated in a growth chamber (Caron 7306, Caron Products and Services, Inc., Marietta, OH, USA) set at 12/12 h daily thermoperiods and two light regimes (12 h light at 30 °C and 12 h dark at 20 °C per day) that were termed as light and dark treatments. Light was provided by a 50-W white fluorescent lamp with the light period coinciding with the high temperature. The temperature used to incubate the seeds was chosen because it was found to be optimal for the germination of these species during preliminary study. Moreover, this temperature regime represents the field conditions between October to early April when there is a higher chance of rain [40].
Light and dark treatments were used to mimic exposed and buried seeds, respectively. The higher temperature regime coincided with the light cycle in the 12 h light photoperiod. Seeds were placed in 9 cm Petri dishes lined with filter paper (Whatman No. 1) moistened with 5 mL of distilled water. Four replications of 25 seeds per Petri-dish were used in each treatment for each species. Constant darkness was maintained by wrapping Petri dishes in two layers of aluminum foil. Germinated seeds were counted and removed daily from the 12 h light treatments, while seeds under the dark treatments were evaluated only at the end of the experiment (after 28 days). Germination was defined as the presence of a radicle (≥2 mm). At the end of the germination trials, all the non-germinated seeds from the 12 h light treatments were dissected to evaluate the embryo status and viability of the non-germinated seeds (living and therefore white; turgid and brown and therefore dead) under a stereo microscope (LEICA).

2.3. Data Analysis

The effect of photoperiod and storage on germination was evaluated separately for each species using a Generalized Linear Model (GLM) with binomial distribution with logit function. The data were analyzed using ®Genstat Software 22nd Edition (VSN International Ltd., Oxford, UK). The photoperiod, storage, and their interaction were explanatory variables in the model. Post-hoc Bonferroni testing was used to determine the differences among the treatment means. Mean germination time (MGT) was calculated using the formula (∑TiNi)/G, where Ti = the day of germination (from planting); Ni = number of seeds germinated at Ti; and G = total number of germinated seeds [41]. Mean germination time (MGT) was calculated separately for each species and analyzed using one-way ANOVA for light treatment only with storage as the factor. Ratio of dead seeds to viable seeds (germinated + dormant) was arcsine transformed and analyzed using one-way ANOVA considering storage as the factor. Non-transformed data is shown in the graph. Relative light germination (RLG) Index [42] was derived by dividing the germination percentage in light by the sum of germination percentage in light and dark. Data on RLG was analyzed using one-way ANOVA for each species separately having storage as the explanatory variable.

3. Results

3.1. Seed Morphological Traits

Seed morphological traits showed a variation among species (Table 2). For example, seed shape was reniform in two species (G. capillaris and A. spinosus) but oblong-inflated, triangular, ovate, and suborbicular in other species. Similarly, the seed coat color and mode of seed dispersal also varied among the species. The seed mass varied from 100.9 ± 0.51 in L. halophilus to 527.4 ± 62.02g in C. pseudosinaica.

3.2. Seed Germination

Seed germination percentages of all the species were affected by both storage and photoperiod, although the effects were species specific (Figure 3). Stored seeds of all the species showed significantly higher germination percentages as compared to the fresh seeds, although the germination percentages of both fresh and stored seeds varied considerably among species. Fresh seeds of four species (i.e., C. pseudosinaica, G. capillaris, A. spinosus, and P. turgidum) had a very low germination percentage (<20%), while P. harmala and L. halophilus seeds showed better germination percentages. Fresh seeds of A. spinosus achieved the lowest (7.0%) and P. harmala achieved the highest germination percentages (64%) in light.
Stored seeds of all the species achieved more than 50.0% final germination percentages, except for A. spinosus. Three species, namely C. pseudosinaica, P. turgidum, and L. halophilus, showed significantly higher germination percentages in the presence of light after storage. Fresh seeds of A. spinosus showed poor germination, irrespective of the presence or absence of light. Stored seeds of A. spinosus exhibited significantly higher germination in dark conditions than the fresh seeds. However, stored seeds of G. capillaris showed significantly higher germination irrespective of the presence or absence of light. A similar trend was detected in P. harmala but the reduction in germination percentage was less than for G. capillaris, especially when the seeds were exposed to light conditions. Additionally, there was no significant increase in the ratio of dead seeds to viable seeds after the storage period in all the species (Figure 4).
The Generalized Linear Model (GLM) analysis indicated that photoperiod (p ≤ 0.025), storage (p ≤ 0.001), and their interaction (p ≤ 0.013) had significant effects on the seed germination of C. pseudosinaica. However, only the main factors (i.e., photoperiod and storage) had significant effects on the seed germination of G. capillaris (photoperiod—p ≤ 0.031; storage—p ≤ 0.001) and L. halophilus (photoperiod—p ≤ 0.007; storage—p ≤ 0.001). Conversely, only storage had significant effects on the seed germination of A. spinosus, P. harmala, and P. turgidum (Table 3).
The RLG Index (Table 4) of fresh seeds was significantly higher than the stored seeds in G. capillaris (p ≤ 0.018) and L. halophilus (p ≤ 0.001). Overall, stored seeds showed lower MGT than the fresh seeds in all the species, except in P. turgidum. However, a significant reduction in MGT has been shown by the stored seeds of C. pseudosinaica, G. capillaris, and L. halophilus (Table 5).

4. Discussion

Seeds play a vital role in plant restoration because most of the restoration projects are generally initiated from seed. Therefore, understanding the longevity of long-term in-situ stored seeds through germination assessment is crucial for (i) recognizing their ability to form persistent soil seed banks and (ii) identifying the potential of in-situ stored seeds for ecosystem restoration. The ability to remain persistent in soil seed banks for long periods of time could be an important strategy that may assist in avoiding sporadic events above ground by contributing to post-disturbance regeneration. The current study revealed that all the test species have the ability to remain persistent in soil seed banks without losing their viability. However, interspecific variation was observed in seed traits (i.e., seed mass, shape, and color) among the studied species. This interspecific variation could be the reflection of genetic differences among the species [50]. Nevertheless, seed traits (i.e., color, shape, and mode of dispersal) did not show any relation with germination, indicating that these traits are not sufficient to predict the germination performance. Therefore, further investigation incorporating other closely related species is required in order to understand the impact of these traits on germination.
Freshly matured seeds of P. harmala and L. halophilus were able to germinate up to 64.0% and 34.0%, respectively. However, fresh seeds of other species exhibited lower germination percentages (<20%) as compared to the stored seeds. These results indicate that the seeds of these species may have different types and levels of dormancy at the time of maturity [51] that prevents the germination of freshly harvested seeds. For example, previous studies reported that C. pseudosinaica, G. capillaris, P. harmala, and P. turgidum seeds have different levels of physiological dormancy [17,52,53], while A. spinosus and L. halophilus seeds are reported to have physical dormancy due to the presence of a hard seed coating that restricts water permeability [18].
The presence of different levels and types of dormancies at the time of seed maturity could be the survival mechanism in desert species that prevents the germination of freshly matured seeds until the occurrence of favorable conditions for germination and seedling establishment. Seeds of all these species mature and disperse during summer (May to June) when the temperature is extremely high and the chances of rainfall are minimum in their natural habitats. Therefore, possessing dormancy at the time of maturation could be the adaptation strategy that may allow them to escape from extreme environmental conditions during summer. Additionally, retaining dormancy could promote species persistence under desert conditions by assisting in (i) synchronizing the germination timing with favorable seasons, (ii) the formation of seedbanks, and (iii) reducing the competition for resources (i.e., nutrients and water) at the seedling proliferation stage [51,54]. Generally, seed production in deserts is erratic and low due to scanty and irregular rainfall events [21]; therefore, forming seed banks could be the adaptation strategy to survive under such conditions, especially when the production of seeds may be reduced for long periods. Moreover, the lower germination of fresh seeds has been suggested as a survival strategy that ensures species persistence by the formation of soil seed banks, even with the repeated droughts that usually occur in desert environments [55,56].
Our results showed that the stored seeds not only maintained their viability (i.e., germinability) but also enhanced their germination percentage significantly, indicating that seeds of these species had greater ecological longevity. Moreover, in-situ seed storage did not affect seed quality that can cause seed death (Figure 4), demonstrating their ability to remain persistent in the soil seed bank for longer durations and thus could serve as a potential source for species reinforcements by contributing to the restoration of declining plant populations [57,58]. Producing orthodox seeds by desert plants could be the survival strategy that allows these species to survive under such extreme environmental conditions [59,60]. Moreover, retaining high viability under in-situ storage conditions demonstrates that these species produce orthodox seeds (i.e., desiccation tolerant).
Orthodox seeds can remain viable for long periods at high temperatures and in dry soils [61,62]. However, seed moisture content plays an important role in determining seed longevity during the storage period [63]. Therefore, quantifying the relations between temperature and seed moisture content and longevity can assist in the better prediction of the storage life of seeds. Therefore, further experiments are required to be conducted considering all the parameters for better understanding seed longevity under in-situ storage conditions.
An increase in the germination percentages of C. pseudosinaica, G. capillaris, P. harmala, and P. turgidum after storage indicates that in-situ storage might be effective for breaking physiological dormancy in these species. Generally, the interaction of temperature and moisture over time has been reported to be responsible for breaking the physiological dormancy and enhancing the germination in physiologically dormant seeds [17,64,65]. In the present case, stored seeds were exposed to daily (day and night) and seasonal (summer and winter) temperature fluctuations, which might be responsible for alleviating the physiological dormancy by accelerating the after-ripening process [17,66]. Similarly, extreme soil temperatures during summer as well as seasonal temperature fluctuations have been found effective in breaking physical dormancy in various species [18,67,68]. In the present case, stored seeds of A. spinosus showed higher germination but the overall germination percentage was very low (<22%), indicating that factors other than temperature and humidity fluctuations under natural conditions might be responsible for breaking their seed dormancy. Inherent seed physical and physiological properties might be accountable for retaining dormancy in this species [69]. The existence of different types and levels of seed dormancy in the studied species might be advantageous by allowing seeds to germinate at different times (i.e., from few days to years) and consequently would ensure the chances of their population persistence under such extreme environmental conditions. Moreover, the percentages of dead seeds were very low after in-situ storage (<4.0%), indicating that these species have higher longevity and thus have higher chances to remain persistent in soil seed banks for longer durations.
Fresh seeds germinated significantly better in light when compared to dark, indicating that the seeds are light sensitive and hence will germinate better if they remain on or near the soil surface. Previous studies suggested that seeds that require light for germination have higher potential to form persistent seed banks [51,70], which was clearly corroborated by our results. However, storage decreased the light-sensitivity in G. capillaris and P. harmala for germination indicating that the light sensitivity of seeds for germination is affected due to the alteration of phytochrome response during storage [71,72]. Other species showed higher germination in light as compared to dark, indicating the species-specific differences in light sensitivity during storage. Alterations in seasonal temperature and moisture are found to be responsible for changing the seed dormancy status [69]. Changes in light requirements or RLG during storage could provide a better understanding about the changes in light sensitivity, although capturing the light response only based on RLG is difficult because various other factors such as the level of seed dormancy, photon fluence, and temperature also play an important role in determining light sensitivity during germination [42].
Temperature and relative humidity are known to be important factors which play an important role in regulating seed dormancy and viability status during storage [51]. In the present study, mean germination times were lower in the stored seeds, indicating that temperature and relative humidity might have played a role in affecting MGT by altering the dormancy status under storage and consequently reducing the MGT, depending on species as reported previously in various desert species [17,18]. Usually, germination timing is correlated with dormancy alleviation [73] and reduction in MGT by stored seeds may be the adaptation strategy in desert conditions where germination occurs rapidly after a rainfall event [74].

5. Conclusions

Restoration is a costly and challenging task in deserts due to extreme climatic conditions. However, it may be possible to reduce the cost if information about seed persistency and viability in soil seed banks is available. Understanding the ability to maintain seed viability under in-situ storage conditions could be important for developing conservation and restoration programs in arid environmental conditions. Seeds of all the tested species were dormant at maturity; however, in-situ seed storage enhanced the germination percentage and reduced the MGT. The results of the present study suggested that all the studied species have the ability to form persistent seed banks and they can be classified as orthodox seeds in terms of storage behavior. Moreover, the lower percentage of dead seeds after in-situ storage (<4.0%) indicates that these species have higher longevity and thus have higher chances to remain persistent in soil seed banks for longer durations. The ability to remain viable in soil seed banks will possibly give support for direct implications for restoration efforts by serving as a reservoir of regeneration potential.

Author Contributions

M.K.S.: conception and design, manuscript writing, final approval of manuscript; A.B.: conception and design, manuscript writing, visualization, manuscript reviewing; S.J.: manuscript reviewing, editing, and statistical analysis; R.R.T.: manuscript reviewing and editing; M.T.S.: editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Kuwait Institute for Scientific Research (KISR).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The authors would like to thank Munairah Faisal Aljeri, KISR for her help in mapping the seed collection locations.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Seed collection location in Kuwait of (1) Centaurea pseudosinaica; (2) Gypsophila capillaris; (3) Astagalus spinosus; (4) Peganum harmala; (5) Panicum turgidum; and (6) Lotus halophilus.
Figure 1. Seed collection location in Kuwait of (1) Centaurea pseudosinaica; (2) Gypsophila capillaris; (3) Astagalus spinosus; (4) Peganum harmala; (5) Panicum turgidum; and (6) Lotus halophilus.
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Figure 2. Seeds of (A) Centaurea pseudosinaica; (B) Gypsophila capillaris; (C) Astagalus spinosus; (D) Peganum harmala; (E) Panicum turgidum; and (F) Lotus halophilus.
Figure 2. Seeds of (A) Centaurea pseudosinaica; (B) Gypsophila capillaris; (C) Astagalus spinosus; (D) Peganum harmala; (E) Panicum turgidum; and (F) Lotus halophilus.
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Figure 3. Germination percentage (means ± SE) of the fresh and stored seeds under light and dark conditions. Different letters in the bars indicate significant differences among treatments (each species analyzed separately).
Figure 3. Germination percentage (means ± SE) of the fresh and stored seeds under light and dark conditions. Different letters in the bars indicate significant differences among treatments (each species analyzed separately).
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Figure 4. Ratio of dead and viable (germinated + dormant) seeds (means ± SE) of the fresh and stored seeds of the selected species. Different letters in the bars indicate significant differences among treatments (each species analyzed separately). ‘A’ is the comparison between viable seeds of each species and ‘a’ is the comparison between dead seeds of each species.
Figure 4. Ratio of dead and viable (germinated + dormant) seeds (means ± SE) of the fresh and stored seeds of the selected species. Different letters in the bars indicate significant differences among treatments (each species analyzed separately). ‘A’ is the comparison between viable seeds of each species and ‘a’ is the comparison between dead seeds of each species.
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Table 1. Seed collection location and uses of the studied species.
Table 1. Seed collection location and uses of the studied species.
SpeciesFamilyCollection Month (2017) and LocationUsesReferences
Centaurea pseudosinaica CzerepAsteraceaeJune, Mutla,
29°22′29.01″ N, 47°39′59.62″ E		Fo[34]
Gypsophila capillaris (Forsk.) C. ChrCaryophyllaceaeMay, Sulaibia
29°09′44″ N, 47°41′26″ E		M, Fo[35,36]
Astragalus spinosus VahlFabaceaeMay, Julaia
28°53′29.46″ N, 48°14′17.21″ E		M, Fo, Fu, Ss[37]
Peganum harmala L.ZygophyllaceaeJune, Sulaibia
29°09′50″ N, 47°41′05″ E		M, Ss[37]
Panicum turgidum ForsskPoaceaeJune, Sulaibia,
29°06′43″ N, 47°24′51″ E		F, Ss[38,39]
Lotus halophilus Boiss and SprunerFabaceaeMay, Sulaibia
29°09′44″ N, 47°14′17.21″ E		M, Fo, Fu, Ss[37]
M—Medicine, Fo—Fodder, Fu–Fuel, Ss—Sand stabilizing.
Table 2. Seed traits of the studied species.
Table 2. Seed traits of the studied species.
SpeciesLife FormSeed ColorSeed ShapeDispersal Mode *Seed Mass ± SEReference *
C. pseudosinaicaAGrey/brownOblong-inflatedAnemochory527.4 ± 62.0[43]
G. capillarisABlackReniformUnassisted160.0 ± 5.2
A. spinosusPBrownReniformUnassisted294.0 ± 4.2
P. harmalaPBrownTriangularAnemochory/Zoochory120.8 ± 0.9[44,45]
P. turgidumPBlackOvateAnemochory135.7 ± 3.5[46,47]
L. halophilusAYellowSuborbicularHydrochory/Zoochory100.9 ± 0.5[48,49]
A—Annual; P—Perennial. * Denote the references for mode of dispersal.
Table 3. Generalized linear models with binomial distribution of seed germination. Significant values (p < 0.05) are highlighted in bold.
Table 3. Generalized linear models with binomial distribution of seed germination. Significant values (p < 0.05) are highlighted in bold.
FactorPhotoperiod (P)Storage (S)P × S
Centaurea pseudosinaica0.025<0.0010.013
Gypsophila capillaris0.031<0.0010.11
Astragalus spinosus0.207<0.0010.884
Peganum harmala0.385<0.0010.619
Panicum turgidum0.713<0.0010.567
Lotus halophilus0.007<0.0010.727
Table 4. RLG for fresh and stored seeds. Letters indicate significant differences among treatments within each species.
Table 4. RLG for fresh and stored seeds. Letters indicate significant differences among treatments within each species.
SpeciesRLG Index
Fresh SeedStored Seed
Centaurea pseudosinaica0.838 ± 0.09 a0.809 ± 0.01 a
Gypsophila capillaris0.775 ± 0.08 a0.506 ± 0.01 b
Astragalus spinosus0.792 ± 0.13 a0.666 ± 0.01 a
Peganum harmala0.523 ± 0.03 a0.518 ± 0.01 a
Panicum turgidum0.525 ± 0.06 a0.553 ± 0.01 a
Lotus halophilus0.667 ± 0.01 a0.557 ± 0.02 b
Table 5. Mean germination times (days) for fresh and stored seeds under 12 h light per day. Letters indicate significant differences among treatments within each species.
Table 5. Mean germination times (days) for fresh and stored seeds under 12 h light per day. Letters indicate significant differences among treatments within each species.
SpeciesMean Time for Germination (MGT) ± SD
FreshStored
Centaurea pseudosinaica7.0 ± 0.7 a2.8 ± 0.2 b
Gypsophila capillaris7.8 ± 0.7 a4.5 ± 0.4 b
Astragalus spinosus3.6 ± 1.6 a3.4 ± 0.6 a
Peganum harmala4.4 ± 0.6 a3.9 ± 0.1 a
Panicum turgidum5.2 ± 0.8 a5.8 ± 0.4 a
Lotus halophilus4.4 ± 0.4 a2.1 ± 0.2 b
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Suleiman, M.K.; Bhatt, A.; Jacob, S.; Thomas, R.R.; Sivadasan, M.T. Seed Longevity in Desert Species and the Possibility of Forming a Persistent Soil Seed Bank. Sustainability 2023, 15, 15904. https://doi.org/10.3390/su152215904

AMA Style

Suleiman MK, Bhatt A, Jacob S, Thomas RR, Sivadasan MT. Seed Longevity in Desert Species and the Possibility of Forming a Persistent Soil Seed Bank. Sustainability. 2023; 15(22):15904. https://doi.org/10.3390/su152215904

Chicago/Turabian Style

Suleiman, Majda K., Arvind Bhatt, Sheena Jacob, Rini R. Thomas, and Mini T. Sivadasan. 2023. "Seed Longevity in Desert Species and the Possibility of Forming a Persistent Soil Seed Bank" Sustainability 15, no. 22: 15904. https://doi.org/10.3390/su152215904

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