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Morphogenesis in bryophytes

The document summarizes morphogenesis in bryophytes. It discusses that morphogenesis involves all biochemical processes from spore germination to spore formation within the capsule. It involves the phenomena of growth and differentiation. Growth is the synthesis of protoplasm that can occur at the cellular, tissue, organ or organism level. Differentiation leads to the distinction of all plant parts and their specialized functions. Morphogenesis is controlled by exogenous, cytoplasmic and nuclear factors that work coordinately. The development of the sporophyte from gametophytic tissues without gamete fusion (apogamy) and the development of gametophyte from sporophytic tissues without meiosis (aposporous) are also discussed

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MORPHOGENESIS IN BRYOPHYTES Submitted to :- H.C.Negi ( Subject tutor) Submitted by :- Anjna Sharma Roll no. :- 2151018 M.Sc Botany ( 1st Sem.)
MORPHOGENESIS  Morphe :- Form / shape  Genesis :- Origin/ creation.  Defination :- Branch of biology which deals with the origin of form of organisms.  Aim :-  Bryophytes occupies unique position in plant kingdom in between thallophyta and pteridophyta  Identify all metabolic processes which take place in the organism starting from the single cell stage to a full formed organisms.  Bryophytes have gametophytic plant body on which sporophytic phase depends and for supports and nutrition. The spore ( haploid) Form gametophyte ( haploid ) Fusion Zygote( diploid) Forms sporophyte
 The morphogenesis in bryophytes involves the entire biochemistry right from  germination of spore to formation of spore within the capsule.  Phenomenon of morphogenesis :-  It includes two primary functions :-  1. Growth 2. Differentiation.  Growth :-  Growth is a synthesis of protoplasm  Growth can be distinguished in the leval of Cells, tissues , organs or the organisms in order of complexities.  It is based on the principle of kinetics of open system :- Both matter and energy can enter and leave the system .
 Differentiation :-  In which there is a differentiation of all parts of bryophytes and the distinguished functions of every parts.  Process of differentiation leads from the simplicity to complexity in the structure of an organism.  Edmund W. Sinnott ( 1960) has divided the subject of morphogenesis into three parts :-  A) Growth  B) The phenomenon of morphogenesis :- This parts include following aspects such as :-  1. Correlation :- Ganetic correlation , physical correlation.  2. Polarity  3. Symmetry  4. Differentiation.  5. Regeneration.  6.Tissue mixture .  7. Abnormal growth.  C) Morphogenetic factors. :- Light , water, temprature,gravity, chemical factors, growth substances, genetic factors including cytoplasmic and nuclear and, nuclear organization.
 Techniques for the culture of bryophytes :-  Proposed by Bopp and Knoop ( 1984) is basically more or less similar as applied for other plants.  Chopra (1987) has proposed following ten steps for the culture of bryophytes.:-  1. Suitability and selection of bryophyte for culture studies  2. Starting the cultures  3.Glasswares and instrument used.  4.Gadgets used  5.Composition of culture media and then preparation.  6.Culture room conditions.  7.Sterilization of plant material ,glassware, culture media, instrument and inoculation chamber.  8. Inoculation procedures.  9. Special culture technique .  10. Observation and presentation data.
Callus formation :-  For the development of a callus it is necessary to suppress the polarity –an important phenomenon of morphogenesis.It is achieved by nutrilization of internal gradients of nutrients and growth substances.  Differentiation of callus :-  In some bryophytes such as Riccia and Funeria the differentiation in callus usually takes place on the same medium in which they were induced.  In other bryophytes the differentiation is influenced by several morphogenetic factors as reported by Sinnot (1960)  The culture grows in light develop both sporophyte and gametophyte but when grow in dark , they develop only sporophyte as reported in a moss Physcomitrium coorgense.  Kumra (1981) has reported that low temp. enhance the sporophytic differentiation in Funeria hygrometrica . The coconut silk when added in the medium , also enhance the sporophytic differentiation . Physcomitrium
 In morphogenesis, the growth is followed by differentiation . The differentiation is controlled by three ways :-  1. Exogenous control  2. Cytoplasmic control  3. Nuclear control  All the three control are interdependent and work in intimate co-ordination .  The exogenous controls include , light , temp., gravity, and mineral nutrition etc.  The cytoplasmic controls mediate between the exogenous control and nuclear control. In fact, cytoplasmic control is very imp. As it acts as buffer.  Nuclear control is also very important control amongst the three . It is exerted by the genes of the organism .  All the genes are not active at the same time ina given tissue or organ . Some are in state of activity or sone are repressed. Nevertheless they have the capacity to triggered to activity when exposed to appropriate biochemical environment.  It can be better explained by Mehra’s gene block hypothesis which states that there is no fundamental difference in gametophyte and sporophyte generations. In these two generations , it is the different gene systems that are in the activated state.
APOGAMY IN BRYOPHYTES :-  Apogamy means the development of a sporophyte ( embryo) out of any gametophytic cell without the union of male and female gametes.  In bryophytes the sporophyte , which is most simple amongst all the members of embryophyta and consists of foot , seta and capsule , may be produced apogamously from haploid gametophytic tissues which may be protonema buds , rhizoids, or any part of the plant body .  Rashid and chopra ( 1969) got success to produce apogamous sporophytes in Funeria hygrometrica on th axis of the gametophytic plant .  Lal (1963) produced numerous apogamous sporophyte of Physcomitrium coorgense on culture medium containing sugar and coconut milk .
Apospry in bryophytes :-  Apospory means the development of a gametophyte from any part of the sporophyte without any reduction division .  In bryophytes the gametophyte , which is thalloid or leafy in liverworts but only leafy in mosses, is produced aposporously from diploid sporophytic tissues of either foot or seta or capsule.  In mosses the protonema and buds are produced before the formation of the plant , therefore both of them can also be produced aposporously from sporophytic tissues  Rautzens and Matzke (1963) have reported the apospory in Blasia pusilla – a leafy liverwort of order Metzgerials .  Ulychn (1971) has successfully produced aposporous protonema in Dicrancella schreberiana  Pringshein (1876) and stahl (1876) reported the development of protonema from the small fragment of seta . The diploid protonema , later on poduces the axis of the plant . Dicrancella schreberiana Blesia pusilla
MORPHOGENESIS :- Germination of gemma (n) ---- Appearance of rhizoid Initiation of growth from centre  Dorsiventrality of gemma  Differentiation of gametophyte  Physiology of rhizoid formation  Gametangial development(n)  Fusion of gametangia  Diploid zygote formation  Embryo formation  Sporophytic body (2n)  Developing sporophyte  Mature sporophyte ( Male sporangia / female sporangia )  Spores.
ADVENTAGES OF MORPHOGENESIS :-  1. The plants are simple , small in size and gametophytic.  2. Being non – vascular , the cellular complexity is not so much as found in higher plants  3. The zygote , which is diploid and also called the first cell of sporophyte , develop within fertilized archegonium and forms embryo.  4. Embryo forms foot , seta and capsule ( in Riccia only capsule is present and , in Corsinia only capsule and few small celled foot are present and In Sphaerocarpus capsule , small seta and small foot is present.  5. Embryo never forms root , stem, and leaves as in higher plants.  6. Vegetation propagation is common.  7. Both the generations can be studied in the same plant .  8. Life span is short , therefore within a very short duration the experiment can be completed.  9. It is easy to induce callus from gametophyte and sporophyte.
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