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Proceedings of the NationalAcademy of Sciences, India Section B:Biological Sciences ISSN 0369-8211 Proc. Natl. Acad. Sci., India, Sect. B Biol.Sci.DOI 10.1007/s40011-014-0485-6

Response of Datura innoxia Linn. toGamma Rays and Its Impact on PlantGrowth and Productivity

Ibrahim M. Aref, Pervaiz R. Khan,Abdulaziz A. Al Sahli, Azamal Husen,M. K. A. Ansari, Mahmooduzzafar &Muhammad Iqbal

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RESEARCH ARTICLE

Response of Datura innoxia Linn. to Gamma Rays and Its Impacton Plant Growth and Productivity

Ibrahim M. Aref • Pervaiz R. Khan • Abdulaziz A. Al Sahli • Azamal Husen •

M. K. A. Ansari • Mahmooduzzafar • Muhammad Iqbal

Received: 27 August 2014 / Revised: 3 November 2014 / Accepted: 30 December 2014

� The National Academy of Sciences, India 2015

Abstract Dry scarified seeds of Datura innoxia Linn.

were gamma-irradiated with 5, 10, 20, 40, 60 and 80 Gy

radiation, using a cobalt-60 source at the rate of

0.623 Gy min-1 at room temperature, and germinated on

MS-medium in a growth chamber under controlled condi-

tions. Exposure to low dose(s) of radiation (5 Gy) caused

stimulatory effect on seed germination. Analysis of 90-day-

old seedlings revealed that growth rate of root and shoot,

net photosynthetic rate (PN), stomatal conductance (gs) and

the chlorophyll and carotenoid contents increased with

5 Gy radiations. Higher doses proved inhibitory for all the

above parameters; the decline observed was positively

correlated with increase in intensity of gamma radiation.

Intercellular CO2 (Ci), on the other hand, showed an op-

posite trend, being lower with 5 Gy than in the control, but

significantly higher with increased radiation doses. Hyos-

cyamine, a tropane alkaloid, exhibited only irregular and

non-significant variation in its content, with no perceptible

change in structure, in the treated material, indicating that

gamma-irradiation caused no significant alteration in the

quantity or quality of the compound.

Keywords Gamma rays � Hormesis � Hyoscyamine �Seed germination � Seedling growth

Introduction

The amount of secondary metabolites in plants can be

boosted by the application of elicitors, which may be biotic

as well as abiotic. Ionizing radiations, including gamma

rays, are the most widely used abiotic elicitors that can

induce mutation in plants by modifying their physiological

characteristics. Gamma radiation can create free radicals

by reacting with different atoms and molecules within the

cell [1]. Free radicals in turn can damage or modify various

components of plant cells, affecting ultimately the mor-

phology, anatomy, biochemistry and physiology of the

plants as per the intensity of radiation. Photosynthetic pa-

rameters, protein synthesis, lipid peroxidation, enzyme

activity, phenol accumulation and meristematic activity

may be affected in plants raised from gamma-irradiated

seeds [2]. Chromosomal damage in irradiated seeds tends

to inhibit seed germination and seedling growth [3]. Low-

dose irradiation might stimulate growth by altering the

hormonal-signalling network, enhancing the antioxidant

capacity of cells or stimulating cell division [4]. Plant cells

exposed to low radiation may increase in volume; a parallel

increase in the DNA and protein amounts can also occur,

possibly due to synthesis or activation of growth hormones

[3]. On the contrary, higher radiation doses can cause DNA

damage, expression of genes related to callus formation,

and cell-cycle arrest at the G2/M phase during the somatic

cell division [5]. Gamma radiation can change the genetic

I. M. Aref � P. R. Khan

Department of Plant Production, College of Food & Agricultural

Sciences, King Saud University, PO Box 2460, Riyadh 11451,

Saudi Arabia

A. A. Al Sahli

Department of Botany & Microbiology, College of Science,

King Saud University, PO Box 2455, Riyadh 11451,

Saudi Arabia

A. Husen

Department of Biology, College of Natural and Computational

Sciences, University of Gondar, P.O. Box 196, Gonder, Ethiopia

M. K. A. Ansari � Mahmooduzzafar � M. Iqbal (&)

Department of Botany, Jamia Hamdard, Hamdard Nagar,

Tughlaqabad 110062, New Delhi, India

e-mail: iqbalg5@yahoo.co.in

123

Proc. Natl. Acad. Sci., India, Sect. B Biol. Sci.

DOI 10.1007/s40011-014-0485-6

Author's personal copy

structure of plants, enable the economic isolation of mu-

tants with desirable growth and yield components, and

affect plant resistance to disease. The ultimate effect of

radiation can be modified by a variety of factors related to

(a) plant characteristics such as species, cultivar, growth

stage, tissue architecture and genome organization, and

(b) radiation features such as quality, dose and the exposure

duration [3, 6].

The genus Datura of the family Solanaceae produces

alkaloids, such as atropine, scopolamine and hyoscyamine,

which are known to cause therapeutic effects in humans

and animals often through interference with their neuro-

transmitters [7]. Most of the alkaloids are toxic in high

doses, but have important therapeutic utilities in low doses.

Several Datura species are used in the traditional Greeko-

Arab and the Indian systems of medicine and also consti-

tute an important component of a variety of Ayurvedic and

Unani drug formulations. Tropane alkaloids or their ex-

tracts commonly act as analgesic, muscle relaxant, tran-

quilizer, anticholinergic, midriatic and psychotropic drugs.

They have a heavy market demand due to their extensive

use in medicine, and their synthesis is more expensive than

their extraction from plants. The in vitro cell or organ

cultures, except for hairy roots obtained by genetic trans-

formation, could result only in a low-level production of

alkaloids [8].

Induction of mutagenesis for improving the alkaloid

production can be attempted with gamma rays, which are

known for enhancing the production of secondary

metabolites [3]. The present study was undertaken to in-

vestigate the radiosensitivity of Datura innoxia seeds and

identify the useful stimulatory dose range of gamma ra-

diation that can be exploited for inducing mutations of

interest.

Material and Methods

Seed Treatment and Germination

Seeds of D. innoxia Linn., having 14 % moisture, were

taken in homogeneous lots of 50 in glass tubes of 2.25 cm

girth and gamma-irradiated three times with 5, 10, 20, 40,

60 and 80 Gy, at the rate of 0.623 Gy min-1 at room

temperature, using a cobalt-60 source (Gamma chamber

GC-5000, BRIT, India). An untreated seed lot was used as

the control.

The irradiated seeds were scarified manually with sand

paper (#80), disinfected by dipping in ethanol at 70 �C for

30 s and then soaked in sodium hypochlorite at 12 �C for

10 min. These were then rinsed thrice with sterilized dis-

tilled water and dried on sterilized filter paper before put-

ting them for germination on MS medium in petri plates.

The experiment was repeated thrice. The germinated seeds

were transferred individually to glass tubes containing

10 ml of the MS medium and kept in a controlled atmo-

sphere at 22 �C temperature, 51 % relative humidity and

16 h day-1 photoperiod. Sampling was done 90 days after

in vitro sowing for assessing the various growth parameters

in the control as well as radiation-affected samples as per

the standard methods [9].

Photosynthetic Parameters

Moreover, Infra Red Gas Analyzer (LI 6400, LICOR,

Lincoln, USA) was used for measuring the stomatal con-

ductance (gs), intercellular CO2 concentration (Ci) and net

photosynthetic rate (PN) of the leaves of 90-day-old seed-

lings. Fully expanded individual leaves were clamped into

the leaf chambers of the duly calibrated and checked ap-

paratus for 3 min; the parameters were then analyzed by

pressing the log button on the sensor head. Measurements

were taken from 10 leaves for every set of control as

well as irradiated seedlings. The levels of chlorophylls

(a and b) and carotenoids, in both the control and treated

seedlings, were determined following Hiscox and Israel-

stam [10], taking 0.1 g leaf samples in 7 ml dimethyl

sulfoxide (DMSO) in the glass tubes and keeping them in

oven at 65 �C for 4 h. Three ml DMSO was added to

1.0 ml aliquots and the absorbance recorded at 480, 510,

645, and 663 nm, using a DU 640B spectrophotometer

(Beckman, Fullerton, USA). The chlorophyll and car-

otenoid contents were estimated by applying the formulae

of Duxbury and Yentsch [11] and MacLachlan and Zalik

[12] respectively, and expressed in mg g-1 of fresh weight.

Hyoscyamine Estimation

Different concentrations of hyoscyamine stock solution

(ranging from 0.1 to 1.0 mg ml-1) were taken in separate

tubes, and their individual volumes were made up to 0.5 ml

with 95 % ethanol. The solution of each tube was supple-

mented with 0.5 ml ammonia (10 % v/v) and 2.5 ml

chloroform. The volume was then increased to 15.5 ml

with more chloroform and finally to 40 ml with 6 % acetic

acid (in 5 % ethanol). After gentle shaking the mixture was

allowed to settle in a separating funnel. The 0.5 ml of its

upper layer was taken in separate tube and evaporated to

dryness. Further, 0.5 ml of fuming HNO3 was added to the

residue and allowed to evaporate in a water bath. The

residue was dissolved in 5 ml acetone (passed through

anhydrous Na2SO4). To each tube, 0.05 ml of 3 %

methanolic potassium hydroxide was added. Five replicates

of each concentration were scanned at 400–600 nm by

altering the time interval from 2 to 8 min. The wavelength

of the maximum absorbance (peak) was calculated.

I. M. Aref et al.

123

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Absorbances of samples and the standard were finally

measured after 5 min at a wavelength of 556 nm, as de-

scribed in Indian Pharmacopoeia [13]. The absorbance of

different concentrations of the standard were used for

preparation of calibration plot, using the linear regression

analysis. The regression equation obtained was used for

calculating the hyoscyamine content in samples.

The in vitro-raised seedlings were dried in a hot-air oven

at 65 �C for 4 days and then powdered with a mortar and

pestle. To the powdered sample, 0.5 ml of 95 % ethanol

and 0.05 ml of 10 % (v/v) ammonia were added and heated

gently. The sample was then percolated through a filter-

lined funnel with more chloroform, at a flow rate of

1 drop/s until the volume of the percolate reached 15.5 ml.

To this, 24.5 ml of 6 % acetic acid (in 5 % ethanol) was

added and shaken. A 0.5 ml portion of the upper layer was

taken from this solution and evaporated to dryness. The

measured absorbances were calculated using the standard

curve as obtained above and following the method men-

tioned in the Indian Pharmacopoeia [13].

Data Analysis

The data obtained on parameters studied were analyzed by

ANOVA using the software Graphpad prism, version 5.0.

Significance of variation among means was calculated (at

p \ 0.001, p \ 0.01 and p \ 0.05) by applying the Dun-

nett posttest.

Results and Discussion

Seed Germination

Gamma irradiation of D. innoxia seeds affected the rate of

seed germination, with the maximum effect recorded at

20 Gy dose. Higher doses (40–80 Gy) of radiation reduced

the germination rate, touching the lowest (47.45 %) with

60 Gy (R5). Thus, seed-germination rate increased over the

control up to 20 Gy radiation, but declined at higher treat-

ments (Fig. 1). Median lethal dose (LD50), permitting about

50 % seed germination in the present study, hovers around

40–80 Gy radiation that brings about 48–54 % germination.

Stimulation of biochemical and physiological processes

in living systems by low-dose c-irradiation of seeds may

involve hormesis, a phenomenon that refers to the causa-

tion of positive biological responses to low doses of toxin,

nuclear radiation or other stresses through activation of

repair mechanism, leading to improved immunity level of

the biological system involved. This effect, with reference

to seed germination, has been observed in many species,

more recently in Pterocarpus santalinus [14] and

Terminalia arjuna [15]. Radiation may be more stimula-

tory for wet rather than dry seeds [16]. The stimulatory

effect of c-rays on seed germination might stem from ac-

tivation of the RNA or protein synthesis, and even from

radiation-induced elimination of parasites that affect seed

germination [6]. On the other hand, reduced germination

by high doses can be ascribed to inhibition of mitotic di-

vision in the meristematic zones [17].

Seedling Growth

Effect of radiation dose on the average length of 90-day-

old root axis was highly significant at higher (40–80 Gy)

doses, while a similar effect in shoot axis could be obtained

at relatively lower (5–20 Gy) doses. As evident from

Table 1, the average root length under the influence of the

lowest (5 Gy) radiation dose was enhanced (4.02 cm) over

the control (3.66 cm), but declined with higher (10–80 Gy)

doses. It was the shortest (2.60 cm) with 40 Gy, showing

about 29 % variation from the control. On the other hand,

average shoot length increased over the control (6.20 cm)

to become 7.82 cm with low (5 Gy) radiation dose, at-

taining the maximum (8.12 cm) with 20 Gy. Thus the in-

crease in shoot length over the control continued up to

20 Gy, showing the maximum effect (about 31 %) at this

dose, beyond which it declined. Thus the effect on the

average axis length was significant at higher doses in roots

and at lower doses in shoots. However, in general, both the

root and shoot axes were longer under low radiation doses

(5–20 Gy) and shorter at higher ones. On the whole, the

extent of decrease/increase in plant-axis length did not

correspond strongly with the level of radiation dose,

showing that the radiation effect in D. innoxia did not

follow a regular and linear variation pattern.

The biomass of the root and shoot axes also varied more

or less corresponding with their respective lengths. The

root biomass in the control seedlings was 0.92 mg; it

0102030405060708090

100

0 5 10 20 40 60 80Gamma radiation (Gy)

See

d ge

rmin

atio

n (%

)

Fig. 1 Extent of germination of the control (0 Gy) as well as gamma-

irradiated (5–80 Gy) seeds of D. innoxia

Response of Datura innoxia to Gamma Rays

123

Author's personal copy

increased to 1.20 mg under the influence of 5 Gy radiation

and dropped with higher (10–80 Gy) doses, touching the

lowest (0.65 mg) with 60 Gy. Thus, it showed a variation

of 2 % (with Gy 20) to 30 % (with Gy 5) from the control

(Table 1). Similarly, the biomass of shoot (stem ? leaves),

which was 1.82 mg in the control, was enhanced to

2.45 mg with 5 Gy radiation dose. Even with Gy10 and

Gy20, it remained higher than in the control, but dropped

significantly with larger (40–80 Gy) doses to become less

than in the control. The minimum (1.50 mg) biomass was

recorded with 40 Gy dose. Variation from the control

ranged from about 2 (with 80 Gy) to 38 % (with 20 Gy), as

shown in Table 1. The response, showing an almost similar

pattern in both root and shoot, was non-significant in root

but significant with lower doses in the case of shoot.

The low radiation may be stimulatory, while high doses

are often inhibitive for plant growth. It is well documented

for several plant species [18, 19]. In the present study, high

radiation doses could reduce the root and shoot lengths of

D. innoxia up to 29 and 17 %, respectively. Such reduc-

tions have been observed in some other Datura species also

[20]. In vitro shoot tips of Dracaena surculosa exposed to

5, 10 and 15 Gy showed increased axis growth up to

10 Gy, and a decline with 15 Gy radiation level [21].

Moreover, wet seeds of Moluccella laevis exposed to high

doses of gamma rays (12.5–17.5 Kr) caused certain mor-

phological variations in the seedlings [16]. However, in

Triticum aestivum, the length of root and shoot as well as

their fresh and dry weights increased with increase in the

radiation dose, although the relative water content (RWC)

and membrane integrity declined under high doses [22].

Lethal dose of radiation, if selected on the basis of

30–50 % reduction in the length of root and stem axes [20],

seems to start in D. innoxia from 40 Gy, as the authors

noticed about 29 % reduction in root axis at this treatment,

but the shoot length could withstand even 80 Gy radiation.

At low radiation doses, the significant improvement in

the biomass could possibly be due to elevated physio-

logical activities of cells, leading to stimulated cell divi-

sion/cell elongation [3, 18, 23]. However, higher doses

reduced the growth rate, presumably because of alteration

of metabolic processes due to nucleic-acid disruption,

which in turn disturbed the hormonal action. This could

retard the mitotic cell division in the apical meristem [24].

Photosynthetic Traits

The data of Table 2 indicate that the net photosynthetic

rate (PN) was higher (15.26 lM CO2 m-2 s-1) in seedlings

raised from seeds treated with low (5 Gy) gamma radiation

as compared to the control (13.24 lM CO2 m-2 s-1), but it

was consistently low with higher (10–80 Gy) radiation

doses applied. Thus, the lowest (6.10 lM CO2 m-2 s-1)

photosynthetic rate was associated with the highest (80 Gy)

radiation dose.

The stomatal conductance (gs) also showed similar

variation, depicting a slight gain (0.61 mM H2O m-2 s-1)

over the control (0.58 mM H2O m-2 s-1) under the influ-

ence of low (5 Gy) radiation dose and later a constant

decline with the gradual increase in the radiation level,

Table 1 Comparative account of certain parameters related to axis growth in the seedlings of D. innoxia raised from the control as well as

gamma-irradiated (5–80 Gy) seeds

Gamma irradiation (Gy) Parameters

Root length (cm) Shoot length (cm) Root biomass (mg) Shoot biomass (mg)

00 (control) 3.66 ± 0.42 6.20 ± 0.85 0.92 ± 0.30 1.82 ± 0.51

05 4.02 ± 0.58ns

(9.84)

7.82 ± 0.75b

(26.13)

1.20 ± 0.33ns

(30.43)

2.45 ± 0.48c

(34.61)

10 3.42 ± 0.48 ns

(-6.56)

7.65 ± 0.92b

(23.39)

0.84 ± 0.31 ns

(-8.69)

2.08 ± 0.42c

(14.28)

20 3.50 ± 0.56 ns

(-4.37)

8.12 ± 1.22a

(30.97)

0.90 ± 0.23 ns

(-2.17)

2.52 ± 0.46b

(38.46)

40 2.60 ± 0.44a

(-28.96)

5.62 ± 0.76 ns

(-9.35)

0.72 ± 0.20 ns

(-21.78)

1.50 ± 0.31 ns

(-17.58)

60 2.85 ± 0.40b

(-22.13)

5.15 ± 0.62 ns

(-16.93)

0.65 ± 0.18 ns

(-29.35)

1.61 ± 0.38 ns

(-11.54)

80 2.80 ± 0.50b

(-23.50)

5.52 ± 0.80 ns

(-10.97)

0.75 ± 0.22 ns

(-18.48)

1.78 ± 0.32 ns

(-2.20)

Values are the means (±SD) of 10 individual readings. Parentheses include percent variation from the control

ns non-significant versus control by the Dunnett post testa p \ 0.001 versus control, b p \ 0.01 versus control, c p \ 0.05 versus control

I. M. Aref et al.

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showing the maximum loss (0.32 mM H2O m-2 s-1) with

80 Gy, as compared with the control. Intercellular CO2

(Ci), however, showed an opposite pattern, being slightly

less (280 ppm) with 5 Gy than in the control (295 ppm),

but consistently higher with increased levels of radiation.

The maximum (317 ppm) Ci was recorded with 80 Gy.

Concentration of photosynthetic pigments (chlorophylls

a, b and carotenoids) also varied under the effect of ra-

diation, following the variation pattern of PN and gs,

meaning thereby that the lowest-radiation treatment (5 Gy)

showed a positive effect, while all other doses (10–80 Gy)

caused a consistent decline in the concentration of

chlorophyll and carotenoids (Table 2).

Gamma rays often alter various physiological traits of

plants, including those related to photosynthesis. The authors

observed that PN, gs and amount of photosynthetic pigments

were triggered to rise in D. innoxia by the impact of low-dose

radiation, but higher doses had a suppressive effect. How-

ever, the reverse was applied to internal CO2 (Ci). High doses

of gamma rays disturb leaf gas exchange and water status,

apart from protein synthesis and the hormonal and enzymatic

actions. The magnitudes of PN, gs and photosynthetic pig-

ments in Centella asiatica significantly dropped but those of

Ci and E (transpiration rate) increased due to c-irradiation

[25]. Chlorophyll content may either decrease [26] or in-

crease [27] due to irradiation, depending on the species. Low

doses of gamma rays enhance chlorophyll synthesis by ex-

citing the enzyme system along with improvement in yield

components, while higher doses normally prove inhibitive

[1, 28, 29]. The level of photosynthetic pigments, total car-

bohydrate, phenols and proline increased significantly due to

c-radiation in Vigna sinensis grown under salt stress, thus

alleviating the adverse effect of salinity [30]. In Dracaena

surculosa, chlorophyll content was the maximum at 10 Gy,

but carotenoid content increased even at 15 Gy [21]. In

wheat (Triticum aestivum), chlorophyll content decreased

but carotenoid content increased with increasing c-radiation

[22]. Free radicals are produced in the cells due to interaction

of gamma rays with atoms and molecules, especially of

water, and cause damage/alteration to certain components of

plant cells, including the photosynthesis system and an-

tioxidant system [6].

Hyosyamine Estimation

Analysis of hyoscyamine content in the control and the c-

irradiated 90-day-old samples indicated that c-irradiation

affected the hyoscyamine content, but the variation did not

show any consistent or gradual trend of increase/decrease

with the level of radiation applied (Fig. 2). The maximum

hyoscyamine content was recorded with 60 Gy dose. The

general appearance of the alkaloid spectra obtained from

the control and the irradiated samples were almost similar

to that of pure alkaloid (hyoscyamine), the minor vicissi-

tudes being incongruous and negligible, suggesting that

gamma irradiation did not affect the alkaloid structure.

Table 2 Comparative account of certain parameters related to photosynthesis taking place in the leaves of D. innoxia seedlings raised from the

control as well as gamma-irradiated (5–80 Gy) seeds

Gamma

irradiation

(Gy)

Parameters

Net photosynthetic

rate (lM CO2 m-2 s-1)

Stomatal conductance

(mM H2O m-2 s-1)

Intercellular

CO2 (ppm)

Chlorophyll a

(mg g-1 fr. wt)

Chlorophyll b*

(mg g-1 fr. wt)

Carotenoids

(mg g-1 fr. wt)

00 (Control) 13.24 ± 2.20 0.58 ± 0.15 295 ± 10.24 0.70 ± 0.10 0.48 ± 0.20 0.60 ± 0.11

05 15.26 ± 1.92 ns

(15.10)

0.61 ± 0.11 ns

(05.17)

280 ± 12.05 ns

(-05.08)

0.73 ± 0.14 ns

(04.28)

0.51 ± 0.18

(06.25)

0.69 ± 0.09 ns

(15.00)

10 12.10 ± 1.12 ns

(-08.61)

0.52 ± 0.12 ns

(-10.34)

298 ± 12.10 ns

(01.02)

0.66 ± 0.02 ns

(-05.71)

0.46 ± 0.22

(-04.17)

0.55 ± 0.10 ns

(-08.33)

20 11.76 ± 1.09ns

(-11.18)

0.48 ± 0.18ns

(-17.24)

300 ± 14.28ns

(01.69)

0.65 ± 0.09ns

(-07.14)

0.41 ± 0.18

(-14.58)

0.47 ± 0.02ns

(-21.67)

40 9.58 ± 2.14a

(-27.64)

0.41 ± 0.20ns

(-29.31)

309 ± 15.10ns

(04.74)

0.50 ± 0.01ns

(-28.57)

0.31 ± 0.08

(-35.42)

0.40 ± 0.08ns

(-33.33)

60 7.10 ± 1.78a

(-46.37)

0.35 ± 0.18 ns

(-39.65)

311 ± 12.98 ns

(05.42)

0.38 ± 0.05b

(-45.71)

0.25 ± 0.12

(-47.92)

0.32 ± 0.12c

(-46.67)

80 6.10 ± 2.16a

(-53.92)

0.32 ± 0.28c

(-44.82)

317 ± 15.84c

(07.12)

0.32 ± 0.09b

(-54.28)

0.20 ± 0.05

(-58.33)

0.30 ± 0.08c

(-50.00)

Values for PN, gs and Ci are the means (±SD) of 10 individual readings, while those for photosynthetic pigments represent a mean (±SD) of

three replicates. Parentheses include percent variation from the controla p \ 0.001 versus control, b p \ 0.01 versus control, c p \ 0.05 versus control and ns non-significant versus control by the Dunnett post

hoc test

* Post tests were not calculated because p value was greater than 0.05

Response of Datura innoxia to Gamma Rays

123

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Thus, the quality of hyoscyamine did not suffer due to

irradiation, although the quantity varied, as shown by in-

frared spectroscopy. These observations are in line with

those obtained earlier with reference to alkaloid production

in Atropa belladonna [31] and certain Datura species [20].

Nonetheless, gamma irradiation can alter the production of

secondary metabolites, as observed in a variety of plant

species. In Centella asiatica, the total flavonoid contents

were enhanced significantly by c-irradiation, attaining their

maximum after 8 weeks of plant growth [25]. Radiation

also affected the yield and chemical composition of

essential oil in lemon grass [32]. It increased the produc-

tion of phenolic compounds in Phyllanthus odontadenius,

leading to enhanced antimalarial activity of the plant ex-

tract [33].

Conclusion

Radiosensitivity of seeds is important for plant-breeding

programmes. The present results establish that radiation

prior to seed scarification incites LD50 around 40–80 Gy.

On the other hand, about 30 % loss of root occurs at 40 Gy.

Hormetic effect of low radiation dose also manifests in D.

innoxia. Suitable doses for producing mutant lines of this

species may be selected keeping these findings in view.

Acknowledgments The authors thank Dr. Sumira Jan of the Centre

for Research, University of Kashmir, Srinagar, for review of the text

and Mr Zakir A Siddiqui of the Botany Department at Jamia Ham-

dard, New Delhi, for the help of drawings. They also appreciate the

comments and suggestions of two unknown referees who reviewed

this manuscript for PNAS, India.

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e (m

g g-1

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