Current World Environment

Introduction

Himalaya is one of the youngest and largest mountain systems of the world and is known for its great source of organic and ethnic diversity ^1-2, and the richest biodiversity zone in the terms of qualitative and quantitative from the other part of the world ³. The Himalaya are sensitive to environmental change, especially climate change and the response of recent warming on plant species are remarkably visible ⁴, continuous release of greenhouse gases at the current rates or more would result in more warming up during the 21^st century and global temperature would vary between 2.6⁰C and 4.8⁰C ⁵. Pre maturation of seeds because of warming up of environment and stress may pause this harmonization. Seed and sprouts are the important means of tree regeneration in natural forest. Perennial plants regenerate either through seed or vegetative propagules. 

Identification of physical parameters indicating period of maturing just beforehand of dehiscence of the berries is vital to get seeds of extraordinary strength. Gathering of forestry fruits and seeds is significantly assisted by consistent plans of seed development that permits the latest probable assortment ^{2, 6}. Gathering of seeds after dispersal, once they have been exposed to unrestrained environmental situations, can consequence in seeds of poor class ⁷. For many plant species the fate of the next generation depends to a certain degree, on the maturation conditions of the seeds when they are still on the mother plant ⁸. In several class of species, seed maturing has been linked to physical characteristics ^9-10. Further, with evidence of global warming considerable attention has turned to predict the fate of forests trees ¹¹. 

M. esculenta is a shared under-canopy species of Q.leucotrichophora and P. roxburghii forests. The species frequently favours humid locations and repeatedly forms distinguishing clusters of its own in the groups. The class of species is broadly dispersed in sub-tropical Himalayas ¹². The fruits of the species are eaten in raw form and different by-products are also consumed in the processed form. M. esculenta is also used as fuel wood, fodder for animals and popular medicinal plant used to cure different illness and disorders ¹³. The objective of this study is to determine the ascertainment of seed maturation period and relate it with other physical parameters so that its proper seed collection time can be identified for better management.

Material and Methods

The study was conducted at a site located amongst 29⁰23^/N and 79⁰30^/E at an elevation 1720 and 1900 msl elevation. The study sites are situated in Nainital forest division of Kumaun Himalaya. Mean annual temperature of the study site was 14.8⁰C and total annual precipitation was 2138 mm of which two third occurred during rainy season. In spite of high degree of annual precipitation, season of summer and winter are moderately waterless, usually with < 10cm regular precipitation. In the study 30 quadrats 10x10m were used to finish the phytosociological investigation of sapling class. The size and quantity of the samples were determined following ^14-15. The IVI (importance value index) was ascertained as the total of the relative frequency, density and dominance ¹⁶.

A sample of 20 trees was chosen because they had a perfect stem, a well-established top, and a sufficient number of fruits.  Fruit gathering of M. esculenta was on-going from the fourth week of April to the accessibility of fruit till the last week of the month of May. The fruit assortment was accomplished in a straight way from the tree before the seed grew in the research laboratory. For fruit and seed corporeal factors three reproduce of 25 fruit/seeds were taken in use and the dissimilar factors comprises of fruit/seed size (mm²) (length ×width) and weight of 100 fruit/seed. To measure the moisture content of fruit/seed 3 replicates of 75 fruit/seed were in use for all collection days. The moisture content was determined using a fresh mass method in which the fruit/seed was dehydrated for16±1 hour at 103±2°C and then reweighed ¹⁷. Germination experiment was conceded out in a twin chamber seed germinator for every assortment day. Four replicates of 100 seeds each were utilised for germination. For germination 4 replicates of 100 seeds each were used ¹⁸. The process of germination of seeds was conceded out at 25±1ºC on top of paper in seed germinator in a shaded environment. Day-to-day observation was made and germination was calculated after observable protrusion of radical (1mm) arose following Paul ¹⁹.

Results

Tree layer analysis

At the research sites the overall tree thickness was diversed between 295 and 855 ind ha^-1 and entire basal area stretched from 43.76 to 69.14 m² ha^-1. The tree thickness of M. esculenta was 50 to 180 ind ha^-1, sapling thickness ranged from 18 to 80 ind ha^-1 and seedlings thickness was 60 to 140 ind ha^-1. Total basal area of M. esculenta varied between 13.46 and 15.38 m² ha^-1 and IVI was 48.52 to 66.41. 

Fruit Characteristics

The colour of fruit changed from green to dark red amid first and last collection in both the years (Table 1). The average fruit size among 1^st and last collection was diversed from 63.43±0.3 to 91.55±0.2 mm² in year 1 and 76.5±0.17 to 98.73±0.22 mm² in year 2. The average weight of 100 fruits was varied from 28.72±0.15 to 62.1±0.2 g in year 1 and 36.47±0.26 to 63.43±0.3 g in year 2. The mean moisture content of fruits ranged from 60.28±0.38 to 68.78±0.17% in year 1 and 57.27±0.27 to 64.47±0.26% in year 2 between first and last collection (Table 1). 

Table 1: Variation in physical parameters of M. esculenta fruits over collection period.

Table 2: Variations in physical attributes of M. esculenta seed over the collection period.

Seed Characteristics

The mean seed size of M. esculenta between first and last collection varied from 37.6±0.7 to 58.82±0.2 mm² in year 1 and 46.9±0.17 to 60.3±0.26 mm² in year 2. The average weight of 100 seeds was ranged from 8.55±0.19 to 13.87±0.46 g in year 1 and 11.3±0.2 to 15.67± 0.3 g in year 2 (Table 2).

Germination of seeds

The mean germination percentage of M. esculenta seeds ranged from 7.0±0.06 to 61.3±0.67% in year 1 and 14±0.0 to 35.6±0.0% in year 2. The moisture content percentage ranged between 32.1±0.15 and 48.2±0.7% in year 1 and 28.9±0.5 and 41.7±0.3% in year 2 during the germination (Figure 1). The maximum germination was 61.3±0.6% when the moisture content percent was 32.1±0.15% in year 1 and 58.0±0% when moisture content percent was 32.0±0.30% in year 2.

Figure 1: Effect of moisture content on germination of M. esculenta seeds over the collection period. Click here to view Figure

Test statistics of ANOVA test showed that fruits size, heaviness and moistness of 100 fruits were varied pointedly thru the dates of collection and years (p<0.05). Interface among year × date was noteworthy for fruit size and weight of 100 fruits (p<0.05) but was non-significant for moisture content of fruits. The weight of 100 seeds, seed size, moistness of seeds, and germination varied considerably thru the years and on collection dates (p<0.05). The interface among year × date was noteworthy for moistness of seed, germination and seed size (p<0.05) but was not noteworthy for weight of 100 seeds.

A significantly positive correlation was found among seed size & weight of 100 seeds, seed size and germination percent, weight of 100 seeds and germination percent (p<0.01) and a noteworthy adverse correlation was found among seed size and moistness of seeds, weight of 100 seeds and moistness of seeds & moistness f seeds and germination percent of seeds (Table 3).

Table 3: Pearson correlation between different parameters of seeds of M. esculenta

Discussion 

Present research were more aware of the fact that utmost mature & immature fruits & seeds can be differenced in many ways like by alteration in colours, bigger firmness or brittleness, reduced moistness & precise gravity or by alteration in physical measurements ¹⁰. Physical indices like change in colour have been widely used as a workable sign of development for several species ^20-22. In the present study change in colour from olour green to dark red in M. esculenta was establish to be a noble maturity indicator. ²³ It was also found dark red or blackish red as one of indicators of maturity in M. esculenta which is similar to the present study. Change in colour has constantly been suggested as sign of ripeness, was also observed by ²⁴ for Shorea robusta, ²¹ for Cornus macrophylla, ²⁰ for Quercus leucotrichophora and ¹⁰ for Betula utilis. Different colour transformation has continuously been related with fulfilment of maturity; the key motive is that additional indices offer no benefits above these simply experimental indicators ^18.

Besides colour the other physical parameter that is interrelated with maturity is moisture content. Moistness plays a critical role in maturation and alteration in fruit/seed moistness is robust manifestations that ripeness is continuing ¹⁰. Loss of moistness during maturity is a more essential time of seed growth than is obscure by unreceptive notion of seed drying. Decay in moistness in maturing seeds is thoroughly linked to seed maturity ^{2, 20}. In the contemporary research fruit/seed moistness also emerged as a good sign of seed maturity in M. esculenta. According to ²⁵M. esculenta attained maturity when seed moisture content ranged between 30.46 and 31.72%. ²⁶ also reported seed moistness between 29.8 and 34.13% as maturity sign in P. cerasoides. ²³ specified that moistness of 23.4-36.1% can be linked with optimal germination of Pyracantha crenulata. The beginning of moistness loss causes a decay in the physical movement of maturity cotyledons as well as embryo before the seed falls ^24,27. In the current state an understanding of how vegetation will respond to climatic irregularities is required for forecasting the reaction of plants to forthcoming weather variation and to develop an understanding for saving the species. If the regeneration of a species is instable at a dissimilar rate from that of the species make up its environmental settings, this will lead to anticipating of its periodic happenings ²⁸. In Himalaya there are several plantation tree species in which seed maturation is harmonized with the initiation of monsoon, and their seed sustainability is very low ²⁹. 

Conclusion 

Present study showed that colour change of fruit from green to dark red and change in physical parameters such as fruits & seeds size, weight & number of fruits and seeds per 100 gm is a reliable indicator of maturity in M. esculenta. Besides this fruits and seeds moisture content also appear as useful indicator of maturity. M. esculenta seeds attains maturity when the seeds moisture content ranged between 30.46 and 31.72%. The seed moisture content coincided with maximum germination. Thus, the knowledge of seed maturation of this important species can be helpful in promoting this poorly regenerating species.

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