Seed Biology Quiz

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Questions and Answers

What is the primary function of the endosperm within a seed?

The endosperm provides nutrition to the developing embryo within the seed.

Explain the difference between orthodox and recalcitrant seeds in terms of their tolerance to drying.

Orthodox seeds can withstand drying and can be stored for extended periods, while recalcitrant seeds cannot tolerate drying and must be kept in a hydrated state.

Describe the role of the seed coat (testa) in seed dispersal and dormancy.

The seed coat can contribute to dispersal by providing structures like wings or hooks for wind or animal transport, and it can also help induce dormancy through mechanisms like waterproofing or impermeability.

What are the four major stages in seed development? Briefly describe each stage.

Seed development progresses through four main stages: globular embryo, heart-shaped embryo, torpedo embryo, and maturation. The globular embryo is a spherical structure, the heart-shaped embryo develops a distinct cotyledonary axis, the torpedo embryo elongates with a more prominent root, and maturation involves the final development of the seed coat and endosperm. Signup and view all the answers

How does the sensitivity threshold distribution (Xb(i)) of a population affect the time constant for responses to a factor (ΘX)?

The sensitivity threshold distribution of a population (Xb(i)) influences the time constant for responses to a factor (ΘX) by determining the variation in susceptibility to the factor among individuals within the population. Signup and view all the answers

Give an example of an endospermic seed and an example of a non-endospermic seed.

An endospermic seed is rice, and a non-endospermic seed is a pea. Signup and view all the answers

What is the relationship between double fertilization and the development of both the embryo and endosperm?

Double fertilization involves the fusion of two sperm cells from the pollen tube with different cells within the ovule. One sperm fertilizes the egg cell to produce the zygote, which develops into the embryo, while the other sperm fertilizes the central cell with two polar nuclei, giving rise to the endosperm, which provides nutrition to the developing embryo. Signup and view all the answers

Name three examples of recalcitrant seeds and explain why they are challenging to store under conventional seed bank conditions.

Recalcitrant seeds, such as coffee, mango, and avocado, cannot withstand drying and are often difficult to store under conventional seed bank conditions because desiccation leads to their rapid loss of viability. Signup and view all the answers

What types of data are essential for optimizing the selection of accessions in a genebank?

Passport data, characterization data, and evaluation data. Signup and view all the answers

What is the required initial germination percentage for cultivated and wild seeds according to seed storage practices?

Cultivated seeds must have an initial germination percentage greater than 80%, while wild seeds must exceed 60%. Signup and view all the answers

At what temperature and conditions should seeds be stored for long-term preservation?

-20ºC and vacuum-sealed. Signup and view all the answers

What is the primary purpose of storing collection management data in a relational database?

To control the genebank system and link with international databases for easy user access. Signup and view all the answers

What approach does Community Biodiversity Management (CBM) combine for the management of crop genetic resources?

It combines conservation-focused and development-focused approaches. Signup and view all the answers

How does CBM aim to empower farming communities?

By enabling them to identify, conserve, manage, and add value to crop diversity. Signup and view all the answers

What is one of the key aims of Community Biodiversity Management?

To result in more delegation of authority to the community. Signup and view all the answers

What should be monitored regularly in seed storage to ensure effectiveness?

Germination percentage and seed quantity. Signup and view all the answers

What is the significance of the seed microbiome in relation to seed vigour?

The seed microbiome contributes to seed vigour by providing disease resistance and promoting plant growth, which impacts overall seed performance. Signup and view all the answers

How does sterile seed production affect seed performance?

Sterile seed production can decrease germination and plant fresh weights while shifting the microbiome composition. Signup and view all the answers

What factors influence the period of seed viability during storage?

Seed viability is influenced by genetics, quality at collection, treatment post-collection, and storage conditions such as temperature and humidity. Signup and view all the answers

Why is seed vigour considered important for resilient cropping systems?

Seed vigour is crucial for ensuring high germination rates and strong seedlings, which are essential for successful crop establishment. Signup and view all the answers

What are the consequences of seed deterioration for farmers and gene banks?

Farmers face reduced germination rates and less vigorous seedlings, while gene banks risk losing seed quality and genetic variation. Signup and view all the answers

What role do the 19 LEDs play in the VideometerLab?

They are used to identify objects or pixels based on their reflection spectra. Signup and view all the answers

What role do natural biocides play in seed sanitation?

Natural biocides are used to selectively remove seed-borne pathogens without affecting beneficial microbiota. Signup and view all the answers

How does chlorophyll fluorescence analysis indicate the maturity of seeds?

Higher fluorescence levels suggest immature seeds, leading to reduced germination rates. Signup and view all the answers

How does environmental stress affect the vigour of less vigorous seedlings?

Less vigorous seedlings tend to be more susceptible to infections and stress, impacting their growth and survival. Signup and view all the answers

What types of data does the iXEED DataCollector collect?

It collects X-ray, visual, chlorophyll, and hyperspectral radiation data. Signup and view all the answers

What methods are commonly used to analyze seed vigour?

Common methods include assessing germination speed, respiration activity, and cell membrane integrity. Signup and view all the answers

What is the main purpose of using terahertz analysis in seed analysis?

Terahertz analysis can penetrate deep into tissues and discriminate certain seed varieties based on their spectra. Signup and view all the answers

Explain the difference between seed analysis and sorting.

Seed analysis focuses on the quality of seeds, while sorting is primarily concerned with physical characteristics like size and density. Signup and view all the answers

Which newer techniques are anticipated for future seed analysis?

Techniques such as 3D X-ray, Raman spectroscopy, terahertz analysis, and delayed luminescence are expected to emerge. Signup and view all the answers

What does the ex situ approach in the management of plant genetic resources entail?

The ex situ approach involves conserving and managing plant genetic resources outside their natural habitat. Signup and view all the answers

What potential does the current food production have for global food security?

The potential amount of produced food is sufficient to provide over 2000 kcal per capita per day. Signup and view all the answers

Explain the concept of inoculum threshold in relation to seed-borne diseases. How does this concept relate to the potential for economic loss?

Inoculum threshold refers to the minimum level of infection on or within seeds that will significantly impact disease development and lead to economic loss. If the initial inoculum level exceeds the threshold, the disease will likely progress and cause significant damage to the crop, resulting in reduced yield and revenue. Signup and view all the answers

Describe the 'minimum tolerance level' strategy for controlling seed-borne diseases. Provide one example of a specific crop and pathogen where this strategy is applied.

The minimum tolerance level strategy aims to reduce the initial inoculum (X0) to a point where it remains below the inoculum threshold, even under conditions favorable for infection. This strategy involves selecting seed lots with a low initial infection level to minimize the risk of disease development. For example, in lettuce infected with lettuce mosaic virus, the minimum tolerance level is 1/30,000, indicating that seed lots with a lower level of infection are preferred. Signup and view all the answers

What are the advantages of using the Poisson distribution to model seed-borne pathogens?

The Poisson distribution is a useful model for understanding the distribution of pathogens within a seed lot. It accurately reflects the pattern of pathogen occurrence, where the highest numbers of infections tend to have the lowest frequency. This means that most seeds will be relatively free of pathogens, while a smaller proportion will have larger numbers of infections. Signup and view all the answers

Explain why direct inspection of seeds and field crops is essential in detecting seed-borne diseases.

Direct inspection is crucial because there is often a weak correlation between field symptoms and the presence of pathogens in seed lots. This means that visual symptoms on the crop may not accurately reflect the level of infection within the seed. Therefore, both field inspections and seed inspections are necessary for a comprehensive assessment of the disease situation. Signup and view all the answers

Describe the 'soaking' method for seed extraction and its limitations.

The soaking method involves immersing seeds in water to extract pathogens. This method is particularly effective for surface-dwelling pathogens that are easily released. However, it is not suitable for extracting deeper-seated pathogens or pathogens associated with the internal structures of the seed. Signup and view all the answers

What are selective agar media and how are they used in the detection of seed-borne pathogens?

Selective agar media are specifically designed to isolate and identify particular pathogens. They contain specific nutrients, pH levels, and antibiotics that inhibit the growth of other microorganisms while supporting the growth of the target pathogen. This allows researchers to determine the presence or absence of a specific pathogen within a seed lot. Signup and view all the answers

Explain the significance of the blotter test in the detection of seed-borne diseases.

The blotter test is a simple and reliable method for assessing the viability and health of seeds, as well as detecting the presence of seed-borne pathogens. The test involves placing seeds on a moist blotter paper under controlled conditions. The growth patterns and fungal structures observed on the blotter paper can indicate the presence of specific pathogens. Signup and view all the answers

Why is agar testing unsuitable for obligate fungi?

Agar testing is not suitable for obligate fungi because these fungi require a living host to survive and reproduce. They cannot grow independently on artificial media like agar. Therefore, alternative detection methods are needed for these types of pathogens. Signup and view all the answers

What methods do fungi use for passive distribution of dry conidia?

Fungi distribute dry conidia through wind over distances greater than 500m and via droplets up to 10m. Signup and view all the answers

How do sclerotia contribute to fungal survival in soil?

Sclerotia allow certain fungi, like Sclerotinia, to survive longer periods in soil, up to 19 months. Signup and view all the answers

Name two types of pathogens mentioned that have different longevity based on crop residues.

Necrotrophic pathogens can persist as long as the residues remain, while biotrophic pathogens only last as long as the crop is viable. Signup and view all the answers

What is the effect of environmental conditions on seed healing to pathogens?

Environmental conditions directly influence seed-to-seedling transfer of pathogens and the rate of infection. Signup and view all the answers

Which type of fungi is found primarily on the embryo or superficial layers of seeds?

Biotrophic fungi are located on the embryo and sometimes on the superficial layers of seeds. Signup and view all the answers

Why do pathogens have higher longevity in seeds compared to being on the seed surface?

Pathogens have higher longevity when in seeds because they are better protected from adverse conditions. Signup and view all the answers

What adaptations of fungi contribute to higher seed infection rates in greenhouse conditions?

Fungi thrive better in greenhouse conditions, leading to higher seed transmission due to optimized environmental factors. Signup and view all the answers

Explain the effect of soil sterilization on seedling infection rates.

The percentage of infected seedlings is higher in sterile soils compared to unsterile soils. Signup and view all the answers

Flashcards

Inoculum Threshold

The initial amount of a pathogen on or in seed that will significantly affect disease development and result in economic loss.

Minimum Tolerance Level

A strategy to minimize the initial inoculum on seeds to avoid exceeding the inoculum threshold and causing disease even under conditions favoring the pathogen's growth.