Summer Seeds Research Articles

Impact of delayed seed drop on rodent-mediated seed dispersal and predation of pine.

Many plants exhibit a canopy seed bank, where seeds persist within the canopy for prolonged periods, gradually descending over time and potentially influencing seed predation and animal-mediated dispersal. However, the impact of delayed seed drop on animal predation and seed dispersal remains unclear. We used Chinese Armand pine seeds to simulate delayed seed drop of the canopy seed bank by releasing 7800 pine seeds in both winter and the following summer over 2 years, tracking their fates to investigate its effect on seed predation and dispersal by rodents in a pine plantation in southwest China. Results showed significant seasonal differences in seed fate. In summer, seeds experienced higher predation rates (62.08% vs 3.80% in winter) and lower scatter-hoarding rates (4.18% vs 15.40% in winter). Additionally, seeds in summer were dispersed farther (4.20 m vs. 3.56 m in winter) and primarily formed single-seed caches, as opposed to multi-seed caches in winter. Although delayed seed drop increased immediate predation risks, favorable summer conditions allowed for rapid germination, reducing long-term exposure to predation. In conclusion, while delayed seed drop increases immediate predation risks and reduces caching, it concurrently enhances dispersal distances and reduces cache size.

Do winter and summer cohorts of the invasive weed Parthenium hysterophorus differ in seed germination and seedling growth?

AbstractThe highly invasive weed Parthenium hysterophorus flowers during both hot, humid summers and cold, dry winters in Nepal, yet it remains unknown if there are differences in seed germination and seedling growth during these contrasting seasons. We analysed seed germination and seedling growth of summer and winter cohorts of P. hysterophorus in Kathmandu Valley. Seeds were germinated at low (25/15°C) and high (30/20°C) temperatures, 12/12 h photoperiod and complete dark, and at different levels of water stress. Seedlings were grown in a greenhouse to determine biomass allocation and relative growth rate (RGR). Winter seeds had higher seed biomass than summer seeds, and both seed types germinated under complete dark and 12/12 h photoperiod. Summer seeds germinated at significantly lower rates and percentage than winter seeds at the low temperature, but this difference in germination was not present when summer and winter seeds were incubated at the high temperature. Winter seeds had higher germination (percentage and rate) and took a longer time to reach maximum germination than summer seeds at different levels of water stress. Seedling emergence of both seed types declined with increasing soil depth. Seedling RGRs were nearly equal (summer: 73 mg g−1 day−1, winter: 77 mg g−1 day−1). Biomass allocation to stem and leaves were similar in both cohorts but root biomass allocation was higher in the winter than in the summer cohort. Overall, the maternal environmental effect was moderate on seed germination, and weak on seedling growth. Lack of a pronounced difference in the germination and seedling growth of summer and winter cohorts of P. hysterophorus suggests a wide environmental tolerance of the species, and this could be one of the reasons for the species' ability to invade diverse climatic and geographic regions globally.

Yuan Longping, a great world hunger fighter

Yuan Longping, a great world hunger fighter

Patterns of Seed Dispersal in Coastal Dune Plant Communities

Seed dispersal is a key determinant of species distribution, although it is still unclear how it contributes to species assembly in plant communities. We linked patterns of seed dispersal to coexisting species to investigate the role of dispersal in the species assembly process. We focused on 19 species coexisting in a foredune plant community, classified as “foredune foundation species”, “semi-fixed dune species,” and “alien species”. The number of seeds dispersed by the 19 species was monitored monthly in 25 plots for 12 months. Then we compared both dispersal strategies and dispersal phenology among the species. Foredune foundation species, species of the semi-fixed dune, and alien species used the same dispersal strategies, with the exception of hemerochory, which was prevalently used by alien species. The three groups of species differentiated the dispersal season: semi-fixed dune species and alien species were early and late dispersers, respectively (spring vs. late summer), while foredune foundation species dispersed seeds in summer. Seasonal differentiation in seed dispersal may play a more important role in the species assembly process than dispersal vectors. Shifts in seasonality due to climate change may influence the timing of seed dispersal and provide species with different colonization opportunities.

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.

Seed integrity, effect of temperature and storage time on germination of <em>Populus luziarum</em> and <em>P. primaveralepensis</em>, endangered subtropical species from Mexico

Background: Populus luziarum and P. primaveralepensis are endemic species of western Mexico; growing in riparian forests they are critically endangered. The best way to conserve their seeds is unknown, which could be limiting for their conservation. Hypothesis: The germinability of both subtropical species is like that of boreal and template Salicaceae species that disperse seeds in spring and early summer, as they germinate quickly with high percentages, and rapidly lose their viability when stored at ambient temperature. Studied species: Populus luziarum and P. primaveralepensis. Study site and dates: Western Trans-Mexican Volcanic Belt. Jalisco, Mexico. October 2019. Methods: The physical integrity of the seeds was assessed by X-ray imaging and compared with germinability. In addition, the effect of storage time (nine weeks) under two temperatures (4 and 21 °C) on the percentage and mean germination rate was evaluated. Results: No significant differences were found between physical integrity and germination in freshly collected seeds for both species. Germination in the first 24 hrs was 91 and 95 % for Populus luziarum and P. primaveralepensis, respectively (week 0). Germination percentages were lower when stored at 21 °C, but P. primaveralepensis was decreased more slowly. Conclusions: Seeds of subtropical Populus respond similarly to those of species from temperate and boreal climates with early seed dispersal, a crucial condition for establishing ex situ reforestation and conservation programs.

Seed maturation time influences the germination requirements of perennial grasses in desert climate of Arabian Gulf.

Qatar has a dry, subtropical desert climate, with minimum annual rainfall and intensely hot and humid summers. Using indigenous grass, those adapted to local conditions have the potential to be used for fodder and can also be used for restoration or rehabilitation of degraded rangelands. Chloris virgata, Coelachyrum brevifolium and Cenchrus ciliaris bloom twice a year from April to May (summer) and September to October (winter) under the nursery condition. Therefore, it is important to understand, how seeds produced in different seasons affect the dormancy as well as germination of these species. Seeds of C. virgata, C. brevifolium and C. ciliaris, three desert grasses, were collected from the plants growing on Shahniya nursery in two different seasons, summer (May) and winter (October). The seeds collected in May (summer) were stored up to winter. However seeds collected in October (winter) were immediately used for experiment. We compared the germination potential of seeds that matured in different season at different alternating temperatures at 15/25, 20/30 and 25/35 °C. Lower temperatures correspond to the dark period, while higher temperatures reflect the light period. Seeds collected in summer season (old seeds) were heavier as compared to seeds collected in winter season (new seeds). Winter seeds of C. virgata seem to be dormant, while summer seeds, germinated well in all the tested temperature regimes. However, C. ciliaris seeds showed opposite trends.

Interactions between a seed-eating neotropical rodent, the Azara's agouti (Dasyprocta azarae), and the Brazilian ‘pine’Araucaria angustifolia

We studied the seed predation and scatter-hoarding behaviour of Azara's agoutis Dasyprocta azarae (Rodentia: Dasyproctidae) in relation to the seeds of the Brazilian ‘pine’, Araucaria angustifolia (Araucariaceae), the rodent's main winter food source. We compared seed-removal rates, seed-caching rates, cache distances and recovery rates between a summer period of food abundance (with a low demand for A. angustifolia seeds and no such seeds naturally available) and a winter period of food scarcity (with a high demand for A. angustifolia seeds). We investigated whether the relative seed value affected the rodent's seed-handling behaviour. We predicted that during the high seed-demand period (winter): (1) cache distances would be greater; (2) fewer seeds would be stored; (3) more seeds would be recovered and the seed-recovery time would be lower. In support of our first two predictions, the caching distances were greater in winter (mean ± SE = 15.67 ± 5.11 m) than in summer (9.40 ± 1.59 m), and agoutis hoarded >9 times more seeds in summer (55) than in winter (6). Our third prediction was not supported, and the proportion of unrecovered caches and buried seed recovery times did not differ between winter (mean ± SE = 3.00 ± 0.00 days, n = 5 seeds) and summer (11.05 ± 3.68 days, n = 20 seeds). The high resource density (during summer) rather than the density of A. angustifolia seeds likely influenced seed fate. Agoutis acted mainly as predators, leaving few intact seeds, caching a low proportion of handled seeds (≅ 8%) and rapidly consuming the caches. Agoutis may cache seeds to keep them safe from competitors on a short-term basis rather than maintaining medium- or long-term reserves for use during food-scarcity periods.

Comparative germination of Tamarix ramosissima spring and summer seeds.

Tamarix ramosissima has bi-seasonal flowering and fruit-setting characteristics. This study compared the morphology and germination characteristics of seeds from Tamarix ramosissima plants during the spring flowering period and the summer flowering period. The results are as follows: there is no significant difference in morphology, such as size and thousand-seed weight, between seeds from different the spring and summer flowering periods. Freshly harvested spring and summer flowering period seeds can both rapidly germinate under the 5/15 °C, 5/25 °C, 15/25 °C or 25/35 °C thermoperiods. Average germination time of the spring flowering period seeds is shorter than that of the summer flowering period seeds, with a TG50 of 2-18 hours (TG50 = the time when germinate percentage reached 50 %). NaCl solutions at concentrations below 0.2 mol/L have no significant effect on the germination of Tamarix ramosissima seeds from either flowering periods. However, at above 0.4 mol/L, higher NaCl concentrations adversely affect the Tamarix ramosissima seeds' germination rates. Seeds from the summer flowering period have higher tolerance of NaCl solutions than seeds from the spring flowering period. Seeds that were incubated in NaCl solution for 8 days cannot recover after being transferred to distilled water (0 % recovery), indicating that NaCl treated seeds permanently lost their germination capability. After storing in room temperature for 2 months, Tamarix ramosissima seeds from both spring and summer flowering periods maintain above 80 % viability. After 2 months, the seed viabilities decrease as the storage time lengthens. The viabilities of seeds from both spring and summer flowering periods decrease to about 40-50 % after storage for 6 months. This study can provide scientific basis for rational utilization of the biological resources in arid desert ecosystems.

Population trends of breeding birds in British woodlands over a 32‐year period: relationships with food, habitat use and migratory behaviour

This paper outlines population trends (with confidence intervals) for 49 species in woodland habitats in Britain as monitored by the British Trust for Ornithology’s (BTO) Common Bird Census (CBC) between 1967 and 1999. Additionally, the possible causes of these population trends are investigated by relating the ecological characteristics of species to the degree of population change they have undergone over different time periods. Over the whole period, 17 species showed significant decreases in abundance and 12 species showed significant increases. Whilst population trajectories were diverse, long‐distance migrants showed more negative trends than other species and the timing of the changes in their populations was related to their wintering latitude, suggesting that these species may be suffering from environmental changes in the non‐breeding season. There was also support for habitat specializations being related to population changes, with species classified as scrub and understorey specialists declining on average, but this was only evident across the entire study period. Additionally, species eating seeds in summer declined and those eating vegetation and making use of the agricultural landscape matrix increased. Therefore wide‐scale factors such as landscape‐scale processes or processes operating outside of Britain appear to be important in addition to local habitat change, especially for long‐distance migrants.

The presence and implications of viable seed in the faeces of invasive free-ranging European Rabbits and Red Foxes

Invasion by weeds and other undesirable plants threatens global biodiversity. However, the role of mammals in maintaining and spreading weeds is often overlooked. Here we confirm that two widely distributed and abundant Australian mammalian pests, the European Rabbit (Oryctolagus cuniculus) and the Red Fox (Vulpes vulpes), can spread viable seed. Our assessment mainly involved determining the number and viability of seeds recovered from faeces of free-ranging individuals inhabiting several areas within the Mediterranean region of south-western Australia, an internationally recognized biodiversity hotspot. In summer, viable seeds were recovered from 3?4% of the rabbit faecal pellets (n = 190) compared to 21?40% of pellets in autumn (n = 235). Ten (77%) of the 13 species of seed identified were weeds. Of the 1,136 seeds recovered, 16% germinated. In all, 13-30% of rabbits passed viable seeds in summer, increasing to 44?73% of rabbits in autumn. In captive wild rabbits, mean passage time of marked seed through the intestinal tract ranged from 4?7 h. This, together with the small home ranges of Australian European rabbits, suggests that they may generally disperse seeds over 1?2 km. Nine to 27% of foxes passed viable seed. Although 48% of scats (n = 62) contained whole seed, only 12.9% of all scats contained viable seed (range 9.1%?19.0%). Viable seeds (4/8) were also recovered from the hides of some shot foxes. In all, 63% (12/19) of seed species identified in the scats and pelts of foxes were weeds. Rabbits (primary dispersal) and foxes (primary, and secondary dispersal via seeds ingested with prey) may be important dispersers of viable seed, and may be essential for less common, but important, long-distance plant dispersal, particularly by some invasive species. Thus, suppression of weeds can be added to the benefits of reducing the abundance of rabbits and foxes to protect the unique biota and agricultural production in southwestern Australia.

Seasonality of seed production and germination trends of Fumana ericoides (Cistaceae) in the west semiarid Mediterranean region

Fumana ericoides, a south Mediterranean shrub, flowers twice a year, in spring and in autumn. Its seeds exhibited marked variation in the degree of dormancy, attributed to an impermeable seed coat, ranging from very low initial dormancy (1.7%) in seeds that matured in winter to total dormancy (100%) in those that matured in late spring/early summer. The level of dormancy increased rapidly with time in the first three months in winter-matured seeds, peaking at 75.5%; decreased with time in the second category; and reached a comparable level in both (25.0% and 23.2%, respectively) after nine months and three months, respectively. From then on, changes in dormancy were similar: seeds that had matured in winter reached the second lowest level of dormancy (28.4%) after 24 months and those that had matured in late spring/early summer seeds after 19 months (32.7%). In every case, the dormancy was at its lowest in autumn–winter, the most favourable season for germination and for the survival of seedlings.

Seasonal differences in mineral content, distribution and leakage of sweet pepper seeds

SummaryPepper seed quality is sensitive to variations in climatic conditions during seed development, which might be associated with accumulation, distribution and leakage of mineral elements from the seeds. This was examined in hybrid seeds of sweet pepper (Capsicum annuum L. cv.‘Hazera’ 1195) in two experiments during two growing seasons. The mean daily temperature (day/night) and daily total radiation receipt during seed development were 27.9/23.2°C and 8.63 kW m−2 in the summer and 18.3/ 14.9°C and 3.18 kW m−2 in the winter, respectively. Seeds developed in the summer had lower percentage of seedling emergence and leaked a larger portion (45%) of their K content into the water medium than in winter‐developed seeds. Summer seeds accumulated more K and Cl, but less P, Mg, Ca and the weight ratio of linoleic acid to oleic acid was lower than in the winter seeds. The season did not significantly affect N, S and total fatty acids. The most abundant element on the seed coat surface was K in the summer and Ca in the winter seeds. The cotyledon and endosperm of the summer seeds contained relatively higher ratios of K and Ca and lower ratios of P and Mg than the winter seeds. Transportation of mineral nutrients appeared to be involved in the effect of heat and moisture stresses on emergence quality of the pepper seeds.

Seasonal differences in mineral content, distribution and leakage of sweet pepper seeds

Pepper seed quality is sensitive to variations in climatic conditions during seed development, which might be associated with accumulation, distribution and leakage of mineral elements from the seeds. This was examined in hybrid seeds of sweet pepper (Capsicum annuum L. cv.‘Hazera’ 1195) in two experiments during two growing seasons. The mean daily temperature (day/night) and daily total radiation receipt during seed development were 27.9/23.2°C and 8.63 kW m−2 in the summer and 18.3/ 14.9°C and 3.18 kW m−2 in the winter, respectively. Seeds developed in the summer had lower percentage of seedling emergence and leaked a larger portion (45%) of their K content into the water medium than in winter-developed seeds. Summer seeds accumulated more K and Cl, but less P, Mg, Ca and the weight ratio of linoleic acid to oleic acid was lower than in the winter seeds. The season did not significantly affect N, S and total fatty acids. The most abundant element on the seed coat surface was K in the summer and Ca in the winter seeds. The cotyledon and endosperm of the summer seeds contained relatively higher ratios of K and Ca and lower ratios of P and Mg than the winter seeds. Transportation of mineral nutrients appeared to be involved in the effect of heat and moisture stresses on emergence quality of the pepper seeds.

Attached to Earth and Refreshed with Fruits, Roots and Seeds in Late Summer and Autumn

Attached to Earth and Refreshed with Fruits, Roots and Seeds in Late Summer and Autumn

MOTHER PLANT NUTRITION AND GROWING CONDITION AFFECT AMINO AND FATTY ACID COMPOSITIONS OF HYBRID SWEET PEPPER SEEDS

ABSTRACT The effect of mineral nutrition status of mother plant on the concentrations of amino and fatty acids and the emergence quality of hybrid sweet pepper seeds (cv. ‘Hazera’ 1195) was studied in two hydroponics experiments. Three concentrations of potassium (K) (0.5, 2.5 and 5.0 mM) combined with NH4–N to NO3–N ratios (mM/mM: 0/6.0, 0.9/5.1, 1.8/4.2 and 3.0/3.0) were conducted during the seasons from spring to summer and from autumn to winter, respectively. Seeds developed in the summer showed lower emergence percentage than those developed in the winter. When the mother plants were supplied by the same nitrogen (N) form and K concentration, the summer seeds contained significant higher K and chloride (Cl), total free amino acids, oleic acids, stearic acid, and palmitoleic acid, but lower phosphorus (P), calcium (Ca), magnesium (Mg), proline and linoleic acid than the winter seeds. No difference was found in the concentrations of N, sulfur (S), palmitic acid and total fatty acids of seeds between the two seasons. Replacing of 3 mM NO3–N (50% of total N) by NH4–N or the reduction of K concentration in the solution from 2.5 mM to 0.5 mM decreased proline, histidine, total amino acids, linoleic acid, and increased the ratio of oleic acid to stearic acid in the summer seeds. The correlation and stepwise regression analysis suggested that the emergence percentage of seeds developed in the summer was positively correlated to the proline concentration, but negatively correlated to the concentrations of Cl and K and the ratio of oleic to stearic acid.

A rare continual flowering strategy and its influence on offspring quality in a gynodioecious plant

The majority of angiosperms have a single annual bout of reproduction; species that flower continually throughout the year are rare. Ochradenus baccatus is a gynodioecious, desert shrub whose principal flowering period is associated with the winter rains, although large individuals also remain in flower during the hot, dry summer. The goal of this study was to examine the reproductive consequences of continual flowering in a large population of O. baccatus in Israel. Over the two years of this study, 60% of individuals flowered continuously. The number of fruit and seeds per fruit were greater in winter. Winter seeds were ∼12% heavier than summer seeds and had significantly higher germination rates (80 vs. 60%, respectively). Although summer seeds were smaller and less likely to germinate, we propose that the benefit derived from their production lies in their ability to capitalize on the first winter rains. These early rain events provide a head start on establishment and growth in the hostile desert environment. Plants that delay reproduction until the onset of rains risk having their offspring face the dry conditions of spring and summer.

Alleviation of salinity stress and the response to temperature in two seed morphs of Halopyrum mucronatum (Poaceae)

Halopyrum mucronatum (L.) Stapf. is a coastal dune grass that produces seeds twice during each growing season. Seeds produced during May (summer seed) were black and heavier (2.8 0.09 mg) than brown seeds (2.1 0.04 mg; winter seed) that were produced in November. There was greater than 95% germination in both seed morphs in the non-saline controls at all temperature regimes, but germination was inhibited more by low than high temperatures in the salinity treatments. Summer seeds were more tolerant of salinity than the winter seeds. Highest germination was obtained in all salinity treatments at a 20/30˚C (12-h night/12-h day) temperature regime for the winter seeds and at 25/35˚C for the summer seeds. Gibberellic acid, thiourea and nitrate partially alleviated the effects of salinity in summer seeds and gibberellic acid, kinetin and betaine were able to alleviate the inhibitory effects of salinity on the germination of winter seeds. The seeds of Halopyrum mucronatum exhibited seed dimorphism and a difference in physiological response in the two seed morphs, which could provide them with multiple opportunities to germinate and establish in the hot, dry, saline and unpredictable maritime coastal-dune environment along the Arabian Sea coast of Karachi, Pakistan.

Intra-population variation in reproductive ecology and resource allocation of the rare biennial species Verbascum sinaiticum Benth., in Egypt

Verbascum sinaiticum Benth. (Scrophulariaceae) is a biennial rosette plant. The species is rare in Egypt and its distribution is restricted to the Sinai peninsula. The investigated population was located in Saint Catherine, Southern Sinai. To assess the reproductive ecology of the species the population dynamics, age-specific survival, resource allocation, energy content, and seed longevity of a natural population were studied. The germinable seed bank represents an average of 0·08% of the seeds in the seed rain. The plants are juvenile during 33% to 67% of their lives. Total seed rain output comes from four different cohorts of adult plants. Seeds produced during the summer constituted 83·5% of the total seed rain. Adult plants 15–18 months in age attained a maximum rosette leafiness of 2·85 m2m−2and a maximum root crown diameter of 2·3 cm. Highly reproductive individuals allocated the least dry mass to their roots. The root/shoot ratio was 0·25. Caloric content reached up to 6·37 kcal g−1dry mass in roots of juvenile plants and 7·5 kcal g−1dry mass in the summer seeds. Seed viability was higher in seeds produced during summer and autumn (9 years) as compared to seeds produced during spring (6 years). Life span ranges between 1 and 2 years, which results in an intra-population variation of survival, resource allocation, energy content, and seed longevity and viability. These variations act as an evolutionary filter, an important asset to increase the genetic diversity and stability of populations in areas with low or periodical rainfall.

Biology of The Southern Brown Bandicoot (Isoodon obesulus) In South-Eastern Tasmania. I. Diet.

The diet of the southern brown bandicoot, lsoodon obesulus, was investigated in south-eastern Tasmania using faecal analysis. Isoodon obesulus consumed a range of invertebrate taxa, including Lumbricid earthworms, isopods, lepidopteran larvae, coleopteran adults and larvae, crickets (Gryllidae) and spiders. Plant material (including monocotyledon, dicotyledon and fern) regularly appeared in faecal samples. Seeds were important during the summer months, while spores from hypogeous fungi featured in the diet year-round. We assessed the opportunism of I. obesulus by comparing diet items in the faeces with items recorded in pitfall traps. Isoodon obesulus utilised crickets and seeds in summer when these items became more abundant. However. there was no evidence of any other items being consumed in proportion to their availability.