Seed bank

Presented by:

Sapna K H

Seed technology

TNAU

SEED BANK

• Seed bank is the reservoir of viable seeds or vegetative propagules.

• 2 types of seed bank:Soil seed bankArial seed bank

Types of Seed Banks-Thompson and Grime (1979)

2 types:

A)Arial seed bank.

B)Soil seed bank.

Transient: persist < 1 yr

Persistent: persist > 1 yr

i. Short term persistant_1 to 5 yrs

ii. Long term-more than 5 yrs (Chenopodium album-40 to 1600)

A species forming no soil seed bank at all (except the dry season between ripening and the first autumnal rains) is Agrostemma githago (Corncockle), which is a formerly widespread cereal weed

Which species form large, persistent SB?

Disturbance spp

Annuals/biennials

Small-seeded spp

Ref: seed bank and its perspective by Junling Ma • Zhimin Liu • Dehui Zeng •Bo Liu

Soil seed bank

• The soil seed bank is the natural storage of seeds, often dormant, within the soil of most ecosystems.

• The study of soil seed banks started in 1859 when Charles Darwin observed the emergence of seedlings using soil samples from the bottom of a lake.

• The first scientific paper on the subject was published in 1882 and reported on the occurrence of seeds at different soil depths.

• Living seeds have been found in or on the soil for different durations ,different seasons , at different depths (buried –light-germinate)(Duvel, 1902;

Grundy et al., 2003; Benvenuti, 2007), in different quantities and in different states of dormancy or procession to germination (Baskin and Baskin,1998)

• In agro ecosystem,the soil seed bank is closely associated to weed studies

a. Weed control programmesb. SCMP-Rational use of Herbicides

• Seeds of several plant species hardly ever enter the soil but persist at its surface or in the litter for many years, prominent examples are the large and hard fruits of Medicago and Neurada, which contain dozens of seeds and can give rise to several plants over several years.

• Plants differ in the duration their seeds remain in the soil and even within a species and among seeds of the same cohort there is variability in the time they spend in the soil seed bank.

Seed longevity:

• Longevity of seeds is very variable and depends on many factors; few species exceed 100 years.

• In typical soils the longevity of seeds can range from nearly zero (germinating immediately when reaching the soil or even before) to several hundred years.

• Some of the oldest still-viable seeds were those of

Lotus (Nelumbo nucifera) found buried in the soil of a pond; these seeds were estimated by carbon dating to be 1,040 years old.

Density:

• The mortality of seeds in the soil is one of the key factors for the persistence and density fluctuation, especially for annual plants.

• Studies on the genetic structure of Androsace septentrionalis populations.

• There are indications that mutations are more important for species forming a persistent seed bank compared to those with only transient seeds.

• The increase of species richness in a plant community due to a species-rich and abundant soil seed bank is known as the storage effect.

Associated ecosystem processes

• The term soil diaspore bank can be used to include non-flowering plants such as ferns and bryophytes.

• In addition to seeds, many plants have vegetative propagules to facilitate forming new plants, migration into new ground, or reestablishment after being top-killed. These propagules are collectively called the soil bud bank, which includes dormant and adventitious buds on stolons, rhizomes, and roots.

Arial seed bank

• A canopy seed bank or aerial seed bank is the aggregate of viable seed stored by a plant in its canopy Canopy seed banks occur in plants that postpone seed release for some reason.

• It is often associated with serotiny, the tendency of some plants to store seed in a cone (e.g. in the genus Pinus) or woody fruits (e.g. in the genus Banksia), until seed release is triggered by the passage of a wildfire.

• It also occurs in plants that colonise areas of shifting sands such as sand dunes. In such cases, the seed is held in the canopy even if the canopy becomes buried; thus the seed is anchored in place until good germination conditions occur.

• Delay in seed release, leading to formation of an aerial seed bank is one way to deal with uncertainties of the environment

• In fire-prone habitats,aerial seed storage is favored when seed production and inter-fire establishment are not ensured

• Aerial seed banks are found in the arid dune ecosystem (Zhang and Maun 1994; Wang and Liang 1995; Liu et al.2005).

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5% smoke 10% smoke 20% smoke Charred wood Charred wood +10% smoke

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Means without shared letters differ at P < 0.05 (Tukey’s Test) Error bars are 1 SD

Effects of fire-related cues on Penstemon barbatus seeds

What is the use of

seed bank to

HUMANS..?????

Seed bank-Conservative of genetic diversity

• Role in genetic diversity and natural restoration as well as to recover endangered plant species. (Red data books document)

• Coleanthus subtilis- today highly endangered or extinct plant species.

• One characteristic of such plants is their capacity to survive in the soil seed bank during unsuitable conditions.

• Due to the longevity of seeds, those species remain present for decades

Reference: K.G. BERNHARDT & E. ULBEL University of Natural Resources and Applied Life Sciences, Department of Integrative biology, Gregor-Mendel-Strasse 33, 1180 Vienna, Austria

Environmental significance

• Re-Constituting natural environment of many ecosystems (by wildfire, catastrophic weather timber harvesting is largely due to the soil seed bank)agricultural operations.

• Forest ecosystems and wetlands contain a number of specialized

plant species forming persistent soil seed banks.

• Before the advent of herbicides a good example of a persistent seed bank species, Papaver rhoeas, sometimes was so abundant in agricultural fields in Europe that it could be mistaken for a crop.

• The absence of a soil seed bank impedes the establishment of vegetation during primary succession, while presence of a well-stocked soil seed bank permits rapid development of species-rich ecosystems during secondary succession