Effects of UV-B Enhanced Solar Radiation on Trigonella foenum-graecum

 

Saravanan, R.*, Dhachinamoorthi D., Senthil Kumar K., Vinodkumar S., Nikhileshbabu M. and     Neeraj J.

Department of Pharma. Biotechnology, QIS College of Pharmacy, Ongole, Andhra Pradesh, India- 523 272

*Corresponding Author E-mail: rssrmcp@yahoo.co.in

ABSTRACT:

Thepotential impacts of an increase in solar UV-B radiation reaching the Earth’s surface have been investigated by numerous research groups during the past decades. Much of this research has focused on the effects of plant growth and physiology under artificial UV-B irradiation supplied to plants in growth chambers or greenhouse. UV –B radiation has been shown to cause alterations in physiological and biochemical processes as well as in plant - morphology. Trigonella foenumgraecum is the medicinal plant has got greater medicinal values and used as traditional medicine. Plants exposed to UV radiation commonly respond to morphological, physiological and biochemical alterations. In this study, the sensitivity and resistance of Trigonella foenumgraecum towards UV-B radiation has been studied.

 

INTRODUCTION:

The sun is the natural source of energy. The sun radiates energy in a wide range of wavelength; most of them are invisible to human eyes. Ultra Violet (UV) radiation is a part of the non-ionizing region of the electromagnetic spectrum which comprises approximately 8-9 % of the total solar radiation.¹ UV radiation from the sun has always played important role in our environment and affects nearly all living organisms. UV-B radiation refers to a specific portion of the Sun’s energy reaching the Earth’s surface². It could be simply stated that UV-B radiation is that portion of the electromagnetic spectrum from 290-320 nanometres.

 

UV-B radiation is the most dangerous shorter radiation where as it alters the DNA of the living organisms. UV-B radiation induces morphological and physiological responses in plants. DNA is the major target of UV-B radiation³. The UV-B also damages photosynthetic pigments, proteins and lipids directly. In some plants, the acclimatization responses to UV-B include an increase in the components of protein synthesis after UV-B treatment⁴. UV-B radiation leads to changes in the various physiological and biochemical characters of the plant especially changes in leaf area, leaf thickening biomass, height of leaf and root, crop production and chemical constituents of the plant ⁵.

 

Fenugreek (Trigonella foenumgraecum L.; Family Leguminoceae) is the plant whose seeds and leaves are used not only as food but also as an ingredient in traditional medicine⁶. Its seeds are used for their carminative, tonic, aphrodisiac effects and as a constituent of the daily diet of general population in Indian subcontinent⁷. Its leaves are consumed widely in India as a green leafy vegetable and are a rich source of calcium, iron, β-carotene and other vitamins^{8, 9,10}.

 

The purpose of the work is to study the effects of enhanced solar UV-B radiation on Trigonella foenumgraecum; the medicinal plant has got greater medicinal values. The physiological and biochemical changes in this medicinal plant undergo due to exposure to enhanced UV-B radiation has been analysed and compared with plants grown under ambient light conditions. Here, the sensitivity and resistance of Trigonella foenumgraecum towards UV-B radiation has been studied.

 

MATERIALS AND METHODS:

Plant material:

Trigonella foenum-graecum(Fenugreek) seeds were purchased from the local market, cleaned and dried. The plants were grown in cups in QIS college pharmacy, Ongole. One set of plants were grown under ambient solar radiation and the other under 30 % UV-B solar radiation. Philips TL 40W/12 sunlamp (Philips, India.) was used to supplement UV-B radiation.

 

Growth of plant:

Separate soil cups were prepared for UV-B treatment and control (ambient). Each experiment side contains 10 soil cups and each cup 20 seeds were sown. The plants were watered regularly, and care was taken to avoid microbial or pest infection during the experimental period. UV-B treatment was given to these plants for 6 hours daily (i.e from 10 am to 4 pm). Then treatment was continued under ambient solar radiation.

 

Determination of growth parameters:

Thephysical parameters like Shoot, Root and Leaf lengths were measured for every two day: i.e 2^nd day, 4^th day, 6^th day,8^th day and10^th day from the randomly selected plants in three kinds of pots.

 

Estimation of absorbance content ^{11, 12}:

Chlorophyll:      

Chlorophyll pigments were extracted in 80% acetone and the amount of total Chl, Chl a, and Chl b was quantified using the formulae:

Chlorophyll a (mg/l)    :            (12.21×A₆₆₃) - (2.81×A₆₄₆)­­­

Chlorophyll b (mg/l)    :           (20.13×A₆₄₆) - (5.03×A₆₆₃)

Total Chlorophyll (mg/l) :        (7.18×A₆₆₃) + (17.32×A₆₄₆)           

 

Carotenoids:

The concentration of total carotenoids was estimated in 80% acetone extracts by measuring the absorbance at 480nm and corrected for the chlorophyll interference.

 

Total carotenoids µg/ml  =

A₄₈₀ + (0.114×A₆₆₃)-(0.638×A645)

Carotenoids (mg/ml)  =

1000A470-(3.27 Chl a) –(104 Chl b)  ÷ 229

 

Antyocyanin¹³:                                                 

Anthocyanins were extracted from the leaves by grinding the leaves in 80% acidified methanol (methanol: water: HCl 80:20:1). After centrifugation, the clear extract was used to estimate the concentration of Anthocyanin by measuring the absorbance at 530 and 657 nm and using the following formula.

 

Anthocyanin (g/Kg)   =   A₅₃₀ – (0.3 A₆₅₇) × 100 /M

µg/g fresh weight     = (A ₅₃₀)-(0.3×A₆₅₇)÷A/g fresh weight

 

Flavonoids¹⁴:     

Leaf bits were placed in 80% acidified methanol for 12 hours at 4˚c in dark to extract the flavonoids. The methanolic extract was used to read the absorbance at 315 nm was using the following formula.

 

Flavonoids (g/Kg)    = A₃₁₅×1000 ÷M        

M =fresh mass of the sample (g)

 

Fresh leaf samples equivalent to 100mg were cut into small pieces and incubated overnight in 5ml of 80% acidified Methanol (80:20:1 of methanol : water : HCl ) at 4˚C in the dark . After centrifugation, remove debris and the absorbance at 315nmwas taken and the flavonoid content was expressed as A µg/g leaf freshweight.

 

RESULTS:

The plant Trigonella foenum-graecum(Fenugreek) grown in the greenhouse under the UV-B radiation had different growth habits and different reactions to UV-B radiation. Comparison of UV-B treated plant Vsambient grown plant shows more physical changes in root length, shoot length and leaf length (Table 1) and Chemical composition Chlorophyll, Carotenoids, Anthocyanin and Flavonoids (Table 2).

 

Physical growth parameters:

During the period, the plants grown under enhanced UV-B radiation showed vigorous growth in height than the plant that was grown under ambient conditions (Figure 1).

 

Changes in chemical parameters:

Photosynthetic pigments:

A.    Chlorophyll:

The changes in the photosynthetic pigments were analysed at different growth periods in plants exposed to ambient and enhanced UV-B radiation. The Total ChlorophyllandChlorophyll.A content was more in enhanced UV-B treated plants, compared ambient treated plants but the Chlorophyll.B content was more in ambient treated plants.

 

B.    Carotenoids:

There was a greater increase in carotenoids level in UV-B treated plants compared to that of the carotenoids level in ambient plant.

 

Non-photosynthetic pigments:

A.    Anthocyanin:

The non-photosynthetic pigment like anthocyanin content was also increased similar like photosynthetic pigments in enhanced UV-B treated plants.

 

B.    Flavonoids:

Flavonoids are the UV-B proceeding pigments, and they are known to accumulate under enhanced UV-B radiation. Though the flavonoids content was more in UV-B treated plants compared to ambient plants.

 

DISCUSSION:

The present work is mainly focused on the effect of enhanced UV-B rays on the medicinal plant, Trigonellafoenum-graecum(Fenugreek). The increased level of UV-B up to 20% had more impacts on morphological and chemical characters of the medicinal plants and that induce various responses.

 

Physical changes:

The impact of UV-B radiation studied for a period of one- month growth by comparing UV-B treated plants with normal sunlight grown plants. The physical characters like root length, stem length and leaf area is profoundly increased in UV-B treated plants^{15, 16}. The process of the increase in length of root and stem was may be due to changes in the phyto-harmones^{17, 18} level, which participate in an elongation process.The effect of UV-B radiation on plant growth under field conditions¹⁹ was more than those grown in ambient grown plants.

 

Changes in photosynthetic and non photosynthetic pigments:

In order to understand the significance of changes to increased UV-B radiation the response of medicinal plant was studied over a period of amonth under field condition. The period of study was carried out by using trifoliate leaves on 5^th, 8^thand10^th day. On studying the various physiological function of the plant, the enhanced UV-B radiation has produced large impacts on various parameters. The physical parameters like leaf area, stem length, root length was significantly increased in UV treated plants(Figure 2). The photosynthetic and non-photosynthetic pigments (chlorophyll, carotenoids,  flavonoids andanthocynins)of UV-B treated plants has increased  compared to be ambient light  growing plants(Figure 3). Present study indicates that the UV-B enhanced radiation brings about positive changes in Trigonellafoenumplant.

 

 

Figure 1.Comparative study on Trigonellafoenum-graecum with UV-B and sunlight.

 

Table1. Comparative study of Physical parameters

 

 

Table2. Comparative study of Chemical constituents

Chemical constituents	Ambient plants	UV-B plants
Chlorophyll- A (mg/l)	28.44	42.83
Chlorophyll-B (mg/l)	42.63	36.09
Total Chlorophyll (mg/l)	71.32	77.12
Carotenoids (mg/ml)	2.32	3.230
Anthocyanins (µg/g)	0.174	0.324
Flavonoids (g/kg)	3190	3550

 

 

Figure 2. A comparative study of Physical parameters on Trigonella foenum-graecum with UV-B and sunlight treated plant

 

Figure 3.A comparative study of Chemical constituents on Trigonella foenum-graecum with UV-B and sunlight treated plant

 

 

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Received on 16.12.2011          Modified on 03.01.2012

Accepted on 14.01.2012         © RJPT All right reserved