The hill zone of West Bengal, India, as one of the six parts of the different geographical zones comprising of three hilly subdivisions, Darjeeling (27˚3'N88˚16'E), Kalimpong (27.06˚N 88.47˚E) and Kurseong (26˚52'40''N 88˚16'38''E) which is situated in northern part of the state West Bengal. The geographical area of this zone is about 3115 sq km, which is 3.5% of the total state area. The elevation of the site is about 3150 mt. above sea level. The highest average rainfall varies from 2500 - 3000 mm of which 80% is received during June to September. Snowfall during first half of January is also very common in areas above 2200 m above sea level. The average maximum and minimum temperatures round the year recorded 34˚C and 7˚C respectively (Table 4).

A plant would survive in a new environment could only be interpreted by its fitness or the ability of forming seeds [17] [23] . Flower morphology was recorded by sampling [23] 30 plants per morphotype (populations of entire leaf margin, sinuate leaf margin and wavy leaf margin) where, from each plant five flowers were recorded. After recording, the average of five flowers in each plant and consequently total average of flowers were done in 30 plants in each of the morphotype population. The three types of morphs were taken into consideration to find out any relevance of difference of results present if any. The results of the floral parameters were given in Table 2. [16] and [26] suggested in their investigations particularly taking into account of different floral parameters in a zoophilous plant and Penstemon centranthifolius of Scorphulariaceae family respectively about the contributing effects of floral parameters on fitness of the population and also type of selection by nature.

The flower parts were taken into account in hermaphrodite and female flowers were i) length, breadth and number of sepals, ii) length, breadth and number of petals iii) length and number of stamens iv) length, breadth and number of anthers v) length and number of style, vi) length, breadth and number of stigma and vii) total length of the flower and viii) total number of flowers in a single plant (Table 2) [16] [17] [22] [23] [26] .

The measurement of flower parts was conducted by venire calliper scale to record the observations of the parameters of flowers of both hermaphrodite and female flowers (Table 2). Numbers of flowers were also taken both in hermaphrodite and female plant and correlation of seed wt with each parameter were done to find out if any relationship with any of the floral trait was found at all in this region.

Correlation matrix in SPSS software was measured for each of the floral traits and relationship between each one of them (Table 3). We also did correlation analysis to identify the magnitude of influence of flower parameters for fitness of a single plant. Relationship of each floral parameter was found as it signals the process of evolutionary phenomenon of selection of nature of a plant during the period of domestication [22] [23] .

The validity of regression model for predicting successful pollination and seed set in a plant was one of the methods for finding out the role of floral traits for pollination by animals or insects in many previous reported investigations [17] [22] -[25] which was investigated in addition to the investigations of breakdown of floral homeostasis in this plant.

Seed yield or seed setting in a plant is the most important signal for domestication of a plant in a new region [22] . [27] utilized a regression model where he did linear regression model while investigating different floral traits and fruit size among the various species of genus Phacelia. Regression analysis was done with each parameter to find out the predictability of the effect of flower parameters with respect to seed yield of the plant. Scatter diagrams were observed to infer the relationship between each parameter and the seed wt of the plant (Figures 3(a)-(e)). Here non-parametric relationships were found to be better fitted for the regression analysis of some floral parameters depending on the r² (co-efficient of variation) values.

It was earlier reported in Linanthus sps., variable expression in petal numbers [15] , in Eichhornia panuculata variable expression in petal numbers was reported [19] and in Mimulus guttatus, variable expression of size of floral organs was found [20] , it was not found or reported by ecologists or scientists very frequently.

From the ecological point of view, the ability of organisms to withstand different environmental insults or stress to produce a predictable phenotype is named as developmental homeostasis [28] [29] . The generalisation of overall process can be presented as a schematic diagram in the following way:

Flow chart

Developmental instability is known to be the estimator of genetic stress [30] which results in disruptive selection and development of deformed structure of floral organs, although quantification developmental homeostasis due to genetic effect is very complex and difficult to explain clearly. [30] gave a view of quantification by measuring out the variability of genetical or phenotypical variance (Vg) or (Vp) in a population, but still it is a very complex process for exact quantification. There were found to be various other factors that affected in a process of genetic instability. Disruption of stabilizing selection is sometimes suddenly observed in a new region where any population is introduced by man or nature depending on the type of stress given by nature [16] . Due to extreme environmental stress of a new region or sudden change in environmental parameters, developmental instability (DI) and fluctuating asymmetry (FI) is observed where a plant population loses its original homology of floral or vegetative structure from its parent habitat (Figure 1 & Figure 2) [29] .

According to [28] , canalization is the process or ability of any organism to produce same phenotype across different environments whereas developmental stability is the ability of a plant or any organism to produce same repetitive phenotype within the same environment. The phenotype may be any vegetative or floral organs of a plant. It means overall robustness of the plant or an organism. DH is the result of continuous process of canalizing selection which helps to reduce the accidental phenotypic variation in any region [14] [21] [31] .

Developmental stability (DS) shows the processes in a plant that reduce phenotypic variation arising from environmental accidents [32] . Breakdown of developmental stability or homeostasis certainly leads to disruptive selection of the plants and consequently changes in vegetative or reproductive organs [14] [15] [19] [20] . Structural differences of an individual female and hermaphrodite flower found in this region and normally found were given in (Table 1) confirm the developmental instability in a region.

Unique flower morphology and Lerner’s hypothesis―According to Lerner’s genetic homeostasis model, 7 important hypotheses are to be mentioned [33] .

i) Sexually reproducing organisms have certain genotypes that develop self regulating developmental patterns and phenotype.

ii) Genetic composition (variation) that enhances natural fitness of the environment at hand is retained through self equilibrium properties.

iii) Developmental and genetic homeostasis is maintained because of the superiority of the heterozygotes in the population.

iv) The evolution of auto regulation requires the evolution of certain levels of obligate heterozygousity in mendelian populations.

v) The appearance of occasional morphological deviants (Phenodeviants) which as demonstrated by Waddington can arise in response to a change in environment―is linked to heterozygousity as “a certain percentage individuals of every generation falls below the threshold of the obligate proportion of loci needed in a heterozygous state to ensure normal development”

vi) Metric traits result from the inheritance of additively acting polygenic systems.

vii) Natural selection―essentially the sum of past evolutionary history―counteracts against attempts to shift populations too rapidly and/or too far from adaptive means to maintain a phenotypic balance between fitness- determining characters.

From the seven hypotheses, the fifth is close for describing the cause DI in floral form in our present investigation. A certain percentage of individuals fall below the threshold of obligate proportion of loci needed for heterozygous state. We presented a model as a contribution to the hypotheses based on legible points about a plant. The plant population which will have minimum amount of heterozygousity undergoes the mutation in one or more genes of co-adaptive gene complexes, causes silent mutation in the complex and does not inhibit the production of necessary proteins or enzymes responsible for floral organogenesis. Especially [34] propounded buffering action of genes and more heterozygousity means more buffering action against adverse environments and he evolved balance theory [34] .

Genotype of a plant is AB/CD responsible for FH where gene A, B, C, and D co adaptive gene complexes responsible for flower initiation, development of flower organs, formation of male and female gametes and subsequent maturation of gametes according to their type of sexuality.

We consider two genes in non-homologous chromosomes responsible for minimum number of genes present for heterozygousity, because one gene in one chromosome does not create any heterozygousity, minimum two genes are required for any heterozygous condition for the formation of co-adaptive gene complex.

i) We assume a condition where more than 50% of mutation will cause lethality of the plant/organism, it would be difficult to produce flowers or even if flowers are produced, it will have abortive stamen or non functional flower genes which will not produce organs of the flower and the plant/organism will die (first condition). Here mutation is extreme and non functional proteins are produced due to non sense mutation where fitness of population is obstructed.

ii) We also assume the conditions where temperature and photoperiodism will cause particular changes in co- adaptive gene complexes and DI/BFH/FA is observed due to shortening of photoperiod length and above the range of average temperature in a particular niche.

Mutation specifically silent mutation takes place in producing the desired product of desired genotype of the floral organs, no frame shift or nonsense mutation takes place due to extreme stress of photoperiod and temperature. There must be the end result of the protein or enzyme even low amount or the amount which will help to produce the consistent desired phenotype and effective gametic cells with consistent meiotic divisions even if there are environmental insults like deviation length of photoperiod or heat or any type of abiotic stress impulse have an effect on plant.

Particular length of the photoperiod or temperature range initiates flowering stage of a plant and shifting of vegetative stage to reproductive stage starts on a critical period of length of photoperiod and range of temperature (First condition). More than the critical range of temperature or length of photoperiod will alter the development of flower organs and DI/BFH/FA is found.

During the month of December, the lowest temperature in this region was found 6.4˚C and highest temperature was recorded 15.1˚C (Table 4). In February, average temperature gradually increases to 20.1˚C as highest and lowest was found 10.6˚C. In the month of March, highest temperature was recorded around 24.1˚C whereas lowest temperature was recorded 12.1˚C. In the month of April, highest temperature was recorded 27.3˚C whereas lowest was recorded 15.2˚C (Table 4). But no initiation of flowering was recorded or found in the overall population in the next months in a year. The appropriate location was found in the elevation 1200m∙asl - 1500 m∙asl according investigations done previously [10] and also from the present investigation where maximum flowering was observed and positive fecundity was observed in North Eastern Himalayan region from the month of December to April.

The fact of differential time of flower initiation can be reasoned and consequently supported by the studies on phenological variation between population of one species either along latitudinal or elevation gradients [18] or between ecologically distinct habitats [35] and because of low temperature regime and short range of photoperiodism.

One of the important reasons for changes in morphology is environmental stress factors where flower structure changes in a new habitat [14] - [16] [19] (Model 2 and Model 3). The change in floral morphology in our investigation may be distinguished as of environmental stress and genetic stress which would be very significant from the evolution point of view and we showed them in Model 3.

The process of random development of number of petals was found (Figure 1 and Figure 2) to be undergoing breakdown of floral homeostasis (Model 2) due to silent mutation. Environmental stress [15] [19] which causes the genetic manipulations and silent mutations in the population ultimately results in breakdown of developmental homeostasis. In this region huge scarcity of rainfall along with low temperature and humidity and short day length (Table 4) was found to imbalance the homeostasis of floral genes (Model 3) and co adaptive gene complexes of the population (Model 3).

We observed three prongs in the upper portion of the stigma (Figure 2) which would draw attention of the pollinators better than earlier settings where three prongs were found in the middle part of the stigma (Table 1) [9] and thus would very likely to enhance the chances pollination and very much significant also from the evolution point of view.

In connection to the genes governing the floral morphology, earlier it was an accepted idea that flowers are relatively constant because of the genetic homogeneity of the genes that regulate the flower morphology [37] - [39] postulated that ‘a genic balance or equilibrium for unknown reason is adaptive and is maintained by natural selection.’ He was close to one of the ideas of Lerner’s seven hypotheses. [40] investigated the constancy of pentamerous corolla in a Linanthus sps generation after generation where he found great degree of variability in floral organs and number of petals when they were exposed to simulation hervivory. [26] found heritability of floral traits in Penstemon centranthifolius in future generations. [41] observed developmental instability and fluctuating asymmetry in floral forms in Brassica campestris family which indicated the changes in floral structures or breakdown of floral homeostasis. [41] reported that it was a case of genetic phenomenon under extreme selection pressure and carried out generation after generation. However detailed study of genetic effect on developmental instability is still not extensively done, only the level of asymmetry was calculated in some cases of quantification of the level of developmental instability in a particular area of research [42] .