| 14575659987 | What is the adaptation to ensure that the embryo has enough nutrients? | Most zygotes only divide after a certain amount of endosperm is formed. | | 0 |
| 14551621950 | Pre-fertilisation | * Several hormonal and structural changes occur which lead to the differentiation and further development of the floral primordium.
*Inflorescences are formed which bear the floral buds and then the flowers.
*In the flower the androecium and the gynoecium differentiate and develop | | 1 |
| 14551646479 | What is a floral primordium | A floral primordium is a group of cells or a tissue in an angiosperm or a flowering plant which gives rise to a flower. It is a tissue or a colony of cells that trigger the formation of an organ before its formation. | | 2 |
| 14551654178 | What is an inflorescence? | An inflorescence is a group or cluster of flowers arranged on a stem | | 3 |
| 14551660973 | What is the androecium? ` | The male reproductive organ consisting of many stamens. | | 4 |
| 14551661707 | What is the gynoecium? | the female part of a flower, consisting of one or more carpels. | | 5 |
| 14551738372 | What is an angiosperm? | a plant of a large group that comprises those that have flowers and produce seeds enclosed within a carpel | | 6 |
| 14551748397 | Describe a typical angiosperm | *the anther is bilobed (it has 2 lobes) with each lobe being dithecous or consisting of 2 thecas (a sheath or a covering) which are separated by a longitudinal groove that runs through the anther. | | 7 |
| 14551832765 | Transverse section of an anther - what is shown | The transverse section of an anther reveals that its lobes form a four-sided (TETRAGONAL) strutcure. It consists of 4 microsporangia located at the corners - two in each lobe. | | 8 |
| 14551862804 | What happens to the microsporangia? | They develop further and become pollen sacs. They extend longitudinally all through the length of an anther and are packed with pollen grains. | | 9 |
| 14551865107 | Structure of microsporangium | *circular
*In a young anther, the microsporangium is surrounded by a 4-layer wall which consists of the epidermis, the endothecium, middle layers and the tapetum (the innermost layer).
*The outer three layers protect and help in dehiscense of anther to release the pollen.
*the innermost wall layer (tapetum) nourishes the developing pollen grain
*cells of the tapetum have a dense cytoplasm and more than one nucleus. | | 10 |
| 14551879531 | what does dehiscense mean? | the splitting along a built-in line of weakness in a plant structure in order to release its contents | | 11 |
| 14551883477 | sporogenous tissue - what is it and where is it found | When the anther is young, a group of compactly arranged homogenous (alike) cells called the sporogenous tissue occupies the centre of each microspoorangium.
Each cell of the sporogenous tissue is capable of giving rise to a microspore tetrad. Each one is a potential pollen or microspore mother. | | 12 |
| 14551932330 | Microsporogenesis | As the anther develops, the pollen mother cells (PMC) of the sporogenous tissue undergo meiotic divisions to form microspore tetrads. | | 13 |
| 14551938785 | What are microspore tetrads | The microspore tetrad is the male gamete formed after microsporogenesis.
The microspores are arranged in a cluster of four cells - the microspore tetrad. | | 14 |
| 14551960300 | What happens to the microspore tetrads? | As the anthers mature and dehydrate the microspores dissociate from each other and develop into pollen grains. | | 15 |
| 14551962419 | What is inside each microsporangium? | thousands of microspores or pollen grains are formed that are released with the dehiscence of the anther. | | 16 |
| 14551965496 | What are pollen grains? | male gametophytes | | 17 |
| 14551967088 | Structure of a pollen grain | *spherical
*25-50 micrometers in diameter
* a prominent 2 layered wall | | 18 |
| 14551970429 | The outer layer of pollen grain | *called exine
*made up of sporopollenin
*sporopollenin is one of the most resistant organic material known
*sporopollenin can withstand high temperatures and strong acids and alkali
*No enzyme can degrade sporopollenin
*Exine has prominent apertures (an opening, hole) called GERM PORES where sporopollenin is absent
*pollen grains are well preserved as fossils because of the presence of sporopollenin
*the exine has many patterns and designs | | 19 |
| 14551977497 | The inner wall of the pollen grain | *called intine
*It is a thin and continuous layer made up of cellulose and pectin
*The cytoplasm of pollen grain is surrounded by a plasma membrane. | | 20 |
| 14551984150 | Which two cells does the pollen grain contain when its mature - explain them | The vegetative cell & generative cell.
// The vegetative cell is bigger, has abundant food reserve and a large irregularly shaped nucleus
//The generative cell is small and floats in the cytoplasm of the vegetative cell
//The generative cell is spindle shaped with dense cytoplasm and a nucleus. | | 21 |
| 14552088223 | Pollen grains shedding in 2-celled stage | In over 60% of angiosperms, pollen grains are shed at this stage of the vegetative cell and generative cell. | | 22 |
| 14552089942 | Pollen grains shedding in 3-celled stage | The generative cell divides mitotically to give rise to the two male gametes before pollen grains are shed. | | 23 |
| 14552093619 | How are pollen grains of many species harmful to humans? | They cause severe allergies and bronchial afflictions in some people often leading to chronic respiratory disorders such as asthma or bronchitis.
*Parthenium (carrot grass) came into India as a contaminant with imported wheat and has become ubiquitous (found everywhere) and causes pollen allergy | | 24 |
| 14552098560 | How is pollen now consumed in western countries and why? | Because pollen grains are rich in nutrients they are sold in tablets and syrups as food supplements.
Pollen consumption has been claimed to increase the performance to athletes and race horses. | | 25 |
| 14552113693 | How quickly do pollen grains lose viability? | In rice and wheat the pollen grains lose viability after 30 minutes whereas in some members of Roseceae, Leguminoseae and Solanaceae they maintain viability for months. | | 26 |
| 14552120800 | To store pollen grains for years which condition is needed and when can it be used? | In liquid nitrogen (-196 degrees)
*can be used as pollen banks in crop breeding programmes | | 27 |
| 14552132142 | What is the term for when the gynoecium consists of a single pistil | monocarpellary | | 28 |
| 14552132957 | What is the term for when the gynoecium consists of more than one pistil | multicarpellary | | 29 |
| 14552141694 | What is syncarpous ? | When the gynoecium consists of more than one pistil, the pistils may be fused together which is called syncarpous | | 30 |
| 14552144449 | What is apocarpous? | When the gynoecium consists of more than one pistil, the pistils may be free which is called apocarpous | | 31 |
| 14552149369 | Parts of a flower FEMALE | Carpel - Female reproductive organ of a flower. Contains the STIGMA, STYLE AND OVARY.
Stigma - landing platform for pollen grains
Ovary - Inside the ovary OVULES are present. Inside the ovary is the OVARIAN CAVITY (LOCULE). The PLACENTA is located inside the ovarian cavity.
Pistil - The ovule producing part of a flower.
Ovule - Has the egg cell
Style - Elongated slender part beneath the stigma. | | 32 |
| 14552173474 | What is placentation? | The arrangement of ovules within the ovary is known as placentation. | | 33 |
| 14552174143 | Basal placentation: | The placenta is at the base (bottom) of the ovary and a single ovule is attached to it. Example: Sunflower, marigold. |  | 34 |
| 14552174599 | Parietal placentation: | containing multiple lines of ovules on the exterior wall within the ovary usually derived from multiple fused carpels.E.g. - mustard and Argemone. |  | 35 |
| 14552175589 | Axile placentation: | ovules attached to the central axis of an ovary with two or more locules. E.g. - China rose, tomato and orange. |  | 36 |
| 14552184339 | Free central placentation: | The ovules are borne on central axis and septa are absent. Example - Dianthus and Primrose |  | 37 |
| 14552188499 | Marginal placentation: | Here the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows. It is characteristic of legumes like pea. |  | 38 |
| 14552210904 | What arises from the placenta? | megasporangia | | 39 |
| 14552211291 | What are megasporangia? | They produce megaspores that give rise to female gametophytes
commonly called ovules | | 40 |
| 14552212388 | Structure of a typical angiosperm ovule | *Ovule is attached to the placenta by a stalk called funicle
*Hilium = It is the point where funicle connects the main body of the ovule.
*Integuments = These are the layers that surround the ovule. There can be outer integument and inner integument. The main function of integuments is to protect the inner tissues.
*Micropyle - The opening which is present at the top of integuments is called micropyle. The main function of micropyle is to allow the entry of the pollen tube into the ovule.
*Nucellus - Enclosed within the integuments is a mass of cells called the nucellus. The primary function of nucellus is to provide nutrition to the developing embryo. Cells of the nucellus have abundant reserve food materials.
*Chalaza - The swollen part of ovule present opposite to micropyle is called chalaza. It is the basal part of the ovule.
*Embryo sac/female gametophyte - It is present in the nucellus and it contains female gamete called egg. | | 41 |
| 14552293945 | What is megasporogenesis? | Formation of megaspores from the megaspore mother cell.
Ovules differentiate a single megaspore mother cell (MMC) in the micropylar region of the nucellus. MMC is a large cell containing dense cytoplasm and a prominent nucleus. The MMC undergoes meiotic division which results in formation of four megaspores. | | 42 |
| 14552414239 | Female Gametophyte (embryo sac) | In majority of flowering plants, one of the megaspores is functional and the other three degenerate.
Only the functional megaspore develops into a female gametophyte (embryo sac)
This method of embryo sac formation from a single megaspore is called MONOSPORIC DEVELOPMENT. | | 43 |
| 14552726364 | What is the term given to the method of embryo sac formation from a single megaspore | MONOSPORIC DEVELOPMENT. | | 44 |
| 14552727184 | What is monosporic development? | the term given to the method of embryo sac formation from a single megaspore | | 45 |
| 14552796475 | Formation of the embryo sac | The nucleus of the functional megaspore divides mitotically to form two nuclei which move to the opposite poles, forming the 2-nucleate embryo sac.
Two more sequential mitotic divisions result in the formation of the 4-nucleate and later the 8-nucleate stages of the embryo sac.
*These mitotic divisions are strictly free nuclear - repeated nuclear divisions occur without cell-wall formation.
After the 8-nucleate stage, cell walls are laid down leading to the organisation of the typical female gametophyte or embryo sac | | 46 |
| 14552825496 | Distribution of cells inside the embryo sac | Six of the eight nuclei are surrounded by cell walls and organised into cells - the remaining two nuclei (called polar nuclei) are situated below the egg apparatus in the large central cell.
Three cells are grouped together at the micropylar end (the bottom) and constitute the egg apparatus.
The egg apparatus consists of two synergids and one egg cell.
The synergids have special cellular thickenings at the micropylar tip called the filiform apparatus. The filiform apparatus guide the pollen tubes into the synergid.
Three cells are at the chalazal end (at the top) and are called antipodals.
Therefore a typical angiosperm embryo sac, at maturity, although 8-nucleate is 7-celled. |  | 47 |
| 14554683787 | Where are the male and female gametes produced in flowering plants? | The pollen grain and embryo sac. | | 48 |
| 14554685972 | Are both types of gametes in flowering plants motile or stationary? | Both male and female gametes are non-motile (stationary) | | 49 |
| 14554688824 | When is pollination necessary? | When both types of gametes are non-motile and they have to be brought together for fertilisation. | | 50 |
| 14555725608 | What is pollination? | transfer of pollen from anther to stigma of a pistil | | 51 |
| 14555731241 | Flowering plants use external agents to achieve pollination. List these. | *insects
*birds
*plants put out colorful and fragrant flowers to attract the insects to aid in the pollination process.
*Wind and water (abiotic)
*animals (biotic) | | 52 |
| 14555742090 | Type of pollination: Autogamy | *Pollination is achieved within the same flower.
*Transfer of pollen grains from anther to stigma of the same flower.
*Normal flowers open and expose their anthers and stigmas therefore complete autogamy becomes rare. Autogamy in such flowers requires synchrony in pollen release and stigma receptivity, and also the anthers and the stigma lie close to each other so that self-pollination can occur. | | 53 |
| 14555755532 | What are cleistogamous flowers? | They do not open at all so their anthers and stigmas aren't exposed so cross-pollination is not possible. Their anthers and stigmas lie close to each other therefore when the anthers dehisce in the flower buds, pollen grains come in contact with the stigma for pollination to occur.
This is why cleistogamous flowers are autogamous as there is no chance of cross-pollination. | | 54 |
| 14555771887 | What are chasmogamous flowers? | They have exposed anthers and stigma | | 55 |
| 14555772511 | What type of flowers do the plants Viola, Oxalis and Commelina produce? | Chasmogamous flowers or Cleistogamous flowers | | 56 |
| 14555773561 | Which plants produce Chasmogamous and Cleistogamous flowers | Viola, Commelina, Oxalis | | 57 |
| 14555781777 | List advantages and disadvantages of cleistogamy? | *The advantage of cleistogamy is that the plant can propagate itself under unfavourable conditions.
*The disadvantage is that there is no variation or evolution | | 58 |
| 14555792571 | Type of pollination: Geitonogamy | Transfer of pollen grains from the anther to the stigma of another flower of the same plant.
Although it is still cross-pollination it is genetically similar to autogamy since the pollen grains come from the same plant. | | 59 |
| 14555798469 | Type of pollination: Xenogamy | Transfer of pollen grains from anther to the stigma of another plant. This is the only type of pollination which brings genetically different types of pollen grains to the stigma. | | 60 |
| 14555830054 | Pollen grains landing on stigma due to wind and water are just chances. To compensate for this uncertainty what do flowers do? | They produce enormous amounts of pollen when compared to the number of ovules available for pollination. | | 61 |
| 14555835145 | Amongst abiotic pollinations which factor is most common? | wind | | 62 |
| 14555835912 | What does wind pollination require? | Wind pollination requires that the pollen grains are light and non-sticky so that they can be transported in wind currents.
They also have well-exposed stamens so that the pollens are easily dispersed into the wind currents. They also have large and feathery stigma so that they can easily trap air-borne pollen grains. | | 63 |
| 14555865090 | Where is wind-pollination common? | In grasses | | 64 |
| 14555866595 | What are the characteristics of wind-pollinated flowers? | They often have a single ovule in each ovary and numerous flowers packed into an inflorescense.
for example the corn cob - the tassels are the stigma and the style which wave in the air to trap pollen grains. |  | 65 |
| 14555881913 | Pollination by water | *quite rare
*limited to 30 genera mostly MONOCOTYLEDONS
*Water is a regular mode of transport for the male gametes among the lower plant groups such as algae, bryophytes and pteridophytes | | 66 |
| 14555890617 | Which genera is pollination by water most common? | Monocotyledons | | 67 |
| 14555929528 | For bryophytes and pteridophytes - why is their distribution limited? | Because of the need for water for the transport of male gametes and fertilisation. | | 68 |
| 14555965706 | Examples of water pollinated flowers | Vallisneria and Hydrilla which grow in fresh water and several marine sea-grasses such as Zostera. | | 69 |
| 14555973480 | What is the most common form of pollination in aquatic plants | Most aquatic plants such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind. | | 70 |
| 14556013222 | How does pollination occur in Vallisneria? | The female flower reaches the surface of water by the long stalk and the male flowers or pollen grains are released on to the surface of water. They are carried passively by water currents. Some of them eventually reach the female flowers and the stigma. | | 71 |
| 14556018150 | Normally how does pollination occur in water pollinated plants? | In plants such as seagrasses, female flowers remain submerged in water and the pollen grains are released inside the water. Some of them reach the stigma and achieve pollination. | | 72 |
| 14556022150 | How are pollen grains adapted for water pollination | The pollen grains are long, ribbon like and they are carried passively in water. They are protected from wetting by a mucilaginous covering. | | 73 |
| 14556028561 | Both wind and water pollinated flowers are not very colourful and do not produce nectar - why? | Flowers are colourful and produce nectar to attract insects like houseflies, butterflies, etc. for pollination by insects. This is not necessary for wind and water pollinated flowers. Therefore, they aren't very colourful and don't produce nectar. | | 74 |
| 14556050714 | What are the most common pollinating agents (insects, animals) | Bees, butterflies, flies, beetles, wasps, ants, moths, birds, bats, some primates like lemurs, some arboreal (tree-dwelling) rodents, reptiles like lizards. | | 75 |
| 14556331765 | How are the majority of insect-pollinated flowers? | *large
*colourful
*fragrant
*rich in nectar
*When the flowers are small, they are clustered into an inflorescence to make them conspicuous (clearly visible). | | 76 |
| 14556542630 | How do flowers that are insect-pollinated attract the insects? | When the flowers are small, they are clustered into an inflorescence to make them conspicuous (clearly visible), this attracts animals from their fragrance and/or colour.
The flowers that are pollinated by flies and beetles secrete foul odours to attract these animals. | | 77 |
| 14556550131 | How do flowers that are insect-pollinated sustain the insects/animals? | To sustain animal visits the flowers have to provide reward to these animals - nectar and pollen grains are the usual rewards.
In some species, floral rewards are providing safe places to lay eggs - the tallest flower of Amorphophallus for eg. | | 78 |
| 14559115422 | How do insect-pollinated flowers use the insects for pollination? | For harvesting the rewards the animal comes in contact with the anthers and the stigma. The body of the animal gets a coating of pollen grains which are generally sticky in animal pollinated flowers. When the animal carrying pollen n its body comes in contact with the stigma it brings about pollination. | | 79 |
| 14560060906 | Examples of when floral rewards are providing safe places to lay eggs | *the tallest flower of Amorphophallus
*species of moth and the plant Yucca - both cannot complete their life cycles without each other. | | 80 |
| 14560071999 | How does the species of moth and the plant Yucca help each other? | The moth deposits its eggs in the locule of the ovary, and in turn the flower gets pollinated by the moth. The larvae of the moths start coming out of the eggs as the seeds start developing. | | 81 |
| 14560075973 | Outbreeding Devices - why it is needed | *Majority of flowering plants produce hermaphrodite flowers (a flower that has both staminate and carpellate parts.)
*Pollen grains are likely to come into contact with the stigma of the same flower.
= Continued self-pollination results in inbreeding depression. |  | 82 |
| 14560084723 | Outbreeding devices - what happens | Flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination.
*In some species, pollen release and stigma receptivity is not synchronised. Either the pollen is released before the stigma becomes receptive or the stigma becomes receptive much before the release of pollen.
*In some other species the anther and the stigma are placed at different positions so the pollen cannot come into contact with the stigma of the same flower.
= this prevents autogamy
*Some species use a genetic mechanism that introduces self-incompatibility. This prevents self-pollen (from the same flower or the flowers of the same plant) from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil.
*Production of unisexual flowers - if both male and female flowers are present on the same plant such as castor and maize (monoecious), it prevents autogamy but not geitonogamy.
*In several species such as papaya, male and female flowers are present on different plants (dioecy) which prevents both autogamy and geitonogamy. | | 83 |
| 14560142260 | Pollen-pistil interaction - why it is needed | Often, the wrong type of pollen lands on the stigma - pollen from the same plant (if it is self-incompatible) or pollen from other species. | | 84 |
| 14560161640 | Pollen-pistil interaction - how it is used | The pistil has the ability to recognise the pollen - whether or not it is compatible. If it is compatible, the pistil accepts the pollen and promotes post-pollination events that leads to fertilisation.
If the pollen is incompatible, the pistil rejects it by preventing pollen germination on the stigma or the pollen tube growth in the style. | | 85 |
| 14560183668 | Pollen-pistil interaction - how are the pistil and pollen connected? | Because of continuous dialogue between pollen grain and the pistil - this dialogue is mediated by chemical components of the pollen interacting with those of the pistil. | | 86 |
| 14560333753 | What happens when the pistil decides that the pollen is compatible? | The pollen grain germinates on the stigma to produce a pollen tube through one of the germ spores.
The contents of the pollen grain move into the pollen tube.
The pollen tube grows through the tissues of the stigma and the style and reaches the ovary.
**IF the the plant's pollen grains are shed at the two-celled condition (vegetative cell and generative cell). In such plants, the generative cell divides and forms the two male gametes during the growth of pollen tube in the stigma
***In plants which shed pollen in the three-celled condition, pollen tubes carry the two male gametes from the beginning. Pollen tube, after reaching the ovary, enters the ovule through the micropyle and then enters one of the synergids through the filiform apparatus --- the filiform appartus present at the micropylar part of the synergids guides the entry of pollen tube. | | 87 |
| 14564301534 | Which events are referred to as "pollen-pistil interaction"? | All the events from pollen deposition on the stigma until pollen tubes enter the ovule. | | 88 |
| 14564308996 | Why is it useful to study the pollen-pistil interaction? | It helps plant breeders to manipulate the pollen-pistil interaction - even in incompatible pollinations, to get desired hybrids. | | 89 |
| 14564435042 | artificial hybridisation | *One of the major approaches of crop improvement programme.
*In such crossing experiments it is important to male sure that only the desired pollen grains are used for pollination and the stigma is protected from contamination (from unwanted pollen). This is achieved by emasculation and bagging techniques | | 90 |
| 14564441751 | What is meant by emasculation? | If the female parent bears bisexual flowers, the removal of anthers from the flower bud before the anther dehisces using a pair of forceps is necessary. | | 91 |
| 14564449237 | How do emasculated flowers have to be protected? What is the name of the process? | They have to be covered with a bag of suitable size - generally made up of butter paper - to prevent contamination of its stigma with unwanted pollen.
This is called bagging. | | 92 |
| 14564453738 | What is done when the stigma of bagged flower attains receptivity? | Mature pollen grains collected from anthers of the male parent are dusted on the stigma and the flowers are rebagged, and the fruits are allowed to develop. | | 93 |
| 14564458676 | When is there no need for emasculation and what is done instead? | If the female parent produces unisexual flowers, there is no need for emasculation. The female flower buds are bagged before the flowers open.
When the stigma becomes receptive, pollination is carried out using the desired pollen and the flower rebagged. | | 94 |
| 14564534012 | Double Fertilisation | After entering one of the synergids, the pollen tube releases the two male gametes into the cytoplasm of the synergid.
One of the male gametes move towards the egg cell and fuses with its nucleus thus completing syngamy. This results in the formation of a diploid cell - the zygote.
The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus (PEN)
The central cell after triple fusion becomes the primary endosperm cell (PEC) and develops into the endosperm while the zygote develops into an embryo. | | 95 |
| 14564689240 | Why is double fetilisation termed "triple fusion"? | Because it involves the fusion of 3 haploid nuclei | | 96 |
| 14564690712 | Why is double fertilsiation termed double fertilisation? | Because the two types of fusions, syngamy and triple fusion take place in the embryo sac -- this only happens in flowering plants. | | 97 |
| 14564708009 | What is post-fertilisation events? | Following double fertilisation, events of endosperm and embryo development, maturation of ovules into seeds and ovary into fruit are collectively termed post-fertilisation events. | | 98 |
| 14564712770 | What is endosperm development? | The primary endosperm cell divides repeatedly and forms a triploid endosperm tissue.
The cells of this tissue are filled with reserve food materials and are used for the nutrition of the developing embryo.
The PEN undergoes successive nuclear divisions to give rise to free nuclei. This stage of endosperm development is called free-nuclear endosperm.
Subsequently cell wall formation occurs and the endosperm becomes cellular.
The number of free nuclei formed before cellularisation varies greatly. Coconut water is free-nuclear endosperm (made up of thousands of nuclei) and the surrounding white kernel is the cellular endosperm. | | 99 |
| 14564733389 | What happens to the endosperm? | It may either be completely consumed by the developing embryo (pea, beans) before seed maturation or it may persist in the mature seed (coconut) | | 100 |
| 14575620887 | Where does the embryo develop? | At the micropylar end of the embryo sac where the zygote is situated. | | 101 |
| 14575707444 | What is the meaning of monocotyledon? | a flowering plant with an embryo that bears a single cotyledon (seed leaf). |  | 102 |
| 14575746576 | What is the meaning of dicotyledon? | a flowering plant with an embryo that bears two cotyledons (seed leaves). |  | 103 |
| 14575878357 | Embryogeny in Dicot | *check book and memorise it!* | | 104 |
| 14579601155 | The seed | In angiosperms, the seed is the final product of sexual reproduction.
It is the fertilised ovule.
Seeds are formed inside fruits. | | 105 |
| 14579700999 | What does the seed consist of? | *seed coats
*cotyledons
*embryo axis | | 106 |
| 14579703224 | Describe a cotyledon | The cotyledons of the embryo are thick and swollen due to the storage of food reserves. | | 107 |
| 14579704758 | What are the two types of mature seeds? | Non-albuminous and ex-albuminous. | | 108 |
| 14579705338 | Describe non-albuminous seeds | Non albuminous seeds are the seeds that do not have residual endosperm because it is completely consumed during embryonic development. | | 109 |
| 14579713567 | Describe exalbuminous seeds | Exalbuminous seeds are the seeds which have the stored food and the cotyledons in a special structure called the kernel. | | 110 |
| 14579714192 | Describe albuminous seeds | Albuminous seeds are the seeds which have food stored in the special nourishing tissue called as endosperm that remains persistent till maturity | | 111 |
| 14579722503 | What is the perisperm? | The layer of nutritive tissue, derived from the nucellus | | 112 |
| 14579730659 | As the seed matures what happens to the integuments of ovules? What about the micropyle? | Integuments of ovules harden as tough protective seed coats.
The micropyle remains as a small pore in the seed coat, which facilitates the entry of oxygen and water into the seed. | | 113 |
| 14579744308 | As the seed matures what happens to the water content, the general metabolic activity and what does it do under different conditions? | The water content is reduced and seeds become dry (only 10-15% moisture).
The general metabolic activity of the embryo slows down.
The embryo may enter a stat of inactivity called dormancy - but if favourable conditions are present (moisture, oxygen and suitable temp) then they germinate. | | 114 |
| 14579763051 | What happens as the ovules mature? | The ovules mature into seeds and the ovary into a fruit.
The wall of the ovary develops into the wall of a fruit called pericarp. | | 115 |
| 14579767178 | What are true fruits? | When the fruit develops only from the ovary. |  | 116 |
| 14579834298 | What are false fruits? | When the fruit develops from the ovary and the thalamus. |  | 117 |
| 14579838670 | What are parthenocarpic fruits? | fruits that develop without fertilisation.
Parthenocarpy can be induced through the growth of hormones and such fruits are seedless. |  | 118 |
| 14579858968 | Advantages of seeds for angiosperms | Within the coating are enough nutrients to enable the plant to grow. Young seedlings are nourished until they can photosynthesise on their own.
Seeds and spores can withstand harsh conditions
The hard seed coat provides protection to the embryo
They are products of sexual reproduction so they provide variation. | | 119 |
| 14579910733 | How are seeds helpful to us? | The dehydration and dormancy of the mature seeds are crucial for storage of seeds which allows agriculture to exist. | | 120 |
| 14579935690 | Apomixis | *form of asexual reproduction that mimics sexual reproduction
*A cell transforms itself into an embryo.
*Seeds are formed without fertilisation
*There are two types of apomixis : recurrent agamospermy and adventive embryony |  | 121 |
| 14579968455 | Type of apomixis: Apospory | *Falls under the category of recurrent agamospermy
*Nucellus cell (diploid) undergoes mitotic divisions to form an embryo sac. All the cells inside that embryo sac will be diploid. If ANY one of those cells inside the embryo sac fuses without a male gamete it will produce a diploid embryo. |  | 122 |
| 14579971389 | Type of apomixis: Diplospory | *Falls under the category of recurrent agamospermy
*Megaspore mother cell (diploid) undergoes mitotic divisions to form an embryo sac. All the cells inside that embryo sac will be diploid. If ANY one of those cells inside the embryo sac fuses without a male gamete it will produce a diploid embryo. | | 123 |
| 14579986766 | Adventive embryony | The formation of an embryo in some position other than within an embryo sac.
*From nucellus and integument for eg | | 124 |
| 14579997543 | What is polyembryony? | two or more embryos developing from a single fertilized egg. | | 125 |
| 14580083663 | Why are apomicts useful? | So that farmers don't have to buy hybrid seeds every year but can still produce hybrids year after year. | | 126 |
