Start Discovering Solved Questions and Your Course Assignments
TextBooks Included
Active Tutors
Asked Questions
Answered Questions
helobial type - endospermthis type of endosperm is intermediate between the nuclear and the cellular types the division of the primary endosperm
nuclear type - endosperm the primary endosperm nucleus divides the cell wall is not laid these nuclei and their division products form a large number
development of endospermin a fertilized embryo sac the primary endosperm nucleus is generally observed below the zygote it divides and further
significance of apomixis apomixis offers the possibility of indefinite multiplication of especially favorable biotypes without any variation due to
parthenogenesis the diploid egg produced in the embryo sacs during diplospory and apospory develops into an embryo without fertilization thus
causes of apomixis apomictic species are generally hybrids or polyploids as a consequence there is irregular meiosis apomixis appears to be
non-recurrent type as mentioned earlier it refers to embryo development in reduced embryo sacs the mechanisms identified for such cases are reduced
organization in non-reduced embryo sacs the fate of a nucleus in the embryo sac depends upon its position many irregularities in the disposition of
gonial apospory and somatic aposporygonial aposporythere is no meiosis the megaspore mother cell enlarges a small vacuole appears above and below the
recurrent type in this type euspory seen in normal cases is replaced by aneuspory diplospory because of irregular meiosis when the spore mother ceil
methods useful in self-incompatibilitymore specific methods useful in overcoming self-incompatibility are mentioned below1 bud pollination in petunia
methods to overcome incompatibility it has been possible to facilitate the germination of incompatible pollen by extracting pollen wall proteins from
biological significance of incompatibility both interspecific and intraspecific incompatibility determines the degree of inbreeding and out breeding
inter specific incompatibility this type of incompatibility is characterized by the prevention of fusion of gametes between members of different
gametophytic incompatibilityin gsi systems callose deposition is not evident on the stigma but is very conspicuous in the pollen tube sometimes the
sporophytic incompatibilitythe recognition and rejection reactions in a ssi system occur on the stigma surface placing barriers for pollen
sporophytic and gametophytic self-incompatibilitybesides the categories based on morphology self incompatibility can be further classified into
the exine layerit consists of two layers inner nexine which is continuous and an outer sexine the sculptured one the outer layer has ornamentations
the intine layeras soon as the tetrads release the microspores the inner layer of the pollen wall intine is formed proteinaceous lamellae are
rejection reactionfor rejection reaction the physiological and biochemical processes are set in the pistil by the recognition reaction specific to
barriers to fertilisationincompatibility can occur anywhere from pollination to syngamy and consequently obstructing fertilisation the pollen fails
homomorphic types - intra specific incompatibilityit is characterized by morphologically indistinguishable mating types within a species a proper
s-genethe s-gene has been suggested to be a super gene complex with several linked genes it is supposed to have at least six may he more
heteromorphic types - intra specific incompatibilityplants of the same species produce flowers that differ in morphology this involves two distyly or
incompatibility - pollination and fertilizationplants growing under natural conditions have a preference for their mating partners the stigma of the