The Interactive  Effect of Cadmium Chloride and Gibberellic Acid on
Nucleic Acid and Enzyme Levels in Cowpea, Vigna unguiculata L.

*Muna Al-Rumaih, *S.S. Rushdy, and **A.S. Warsy
*Department of Botany and Microbiology, **Department of Biochemistry,
College of Science, King Saud University, P.O. Box22452,
Riyadh 11495, Saudi Arabia
(Received 25-3-1422 H; accepted for publication 28-3-1423 H)

Abstract. The effect of different concentrations (0, 20, 40, 80, 160 ppm) of cadmium chloride (CdCl2 ) in  the  presence or absence  of 100ppm  gibberellic acid (GA3)  on  nucleic acid (DNA, RNA) levels  and  on  enzyme (peroxidase, ribonuclease) activities in roots and shoots  of Cowpea (Vigna unguiculata L.) at three growth stages (early, intermediate, late) were investigated .The results revealed  reduction in  nucleic acid levels and stimulation of enzyme activities  in  the  presence of cadmium chloride .These changes  were more significant at higher CdCl2 concentrations and during the early growth stage, and became less significant at the later phenological phases of growth. Application  of GA3 simultaneously with  different concentrations  of CdCl2  tended  to  increase  nucleic acid  levels  and  to  decrease  enzyme  activities ,  particularly  at  lower CdCl2  concentrations  and  during  the intermediate stage followed  by the early  growth stage , thus  pointing  to the  role  of GA3 in reducing the inhibitory effect of CdCl2 .Roots were more affected by CdCl2 treatments and less affected by the combined treatment of CdCl2 and GA3 in comparison to shoots.
Keywords: Cadmium, Gibberellic acid, Peroxidase, Ribonuclease, Nucleic acids, Vigna unguiculata.

Introduction

The reaction of plants to environmental stresses are complex and involves many kinds of physiological and biochemical responses [1]. Various environmental stresses cause important modifications in gene expression in plants [2].  Such modifications may lead to alteration in the behavior of enzymes, accumulation or depletion of certain metabolites such as changes in the rate of protein turnover [3].

Cadmium, as a heavy metal, has become a major environmental pollutant, as it is a by-product of many industrial processes. Like many other metals, Cd was reported to affect the properties of nucleic acids, particularly DNA. It has been shown that Cd causes breakage in DNA.  When cultures of Escherichia coli were grown in the presence of 3 µM Cd, loss of viability of the cells was accompanied by considerable single strand 
breakage of the DNA, with no detectable increase in double strand breaks [4].  Briquet and Wiaux [5] proved that the mechanism of action by which any toxic substance can prevent or retard plant development is intimately associated with RNA synthesis, which controls the synthesis of enzymatic proteins.

Uptake of phytotoxic amounts of metals by higher plants could result in the inhibition of several enzymes and increases the activity of others [6]. 
 
Peroxidase and ribonuclease induction is a general response of higher plants to uptake of toxic amounts of metals [7].

Gibberellins are well known for their striking growth promoting effects [8].  The hormone seems to act at the nuclear level by altering the rate of DNA synthesis, thus cell division. In addition, it has an effect on the rate of gene expression, thus affecting the level of RNA and hence proteins [9]. Nucleic acids isolated from the shoots of light grown dwarf peas in the presence of GA3 showed a higher rate of DNA-dependent RNA synthesis compared to the untreated nuclei [10].  Furthermore, Nitsan and Lang [11] found that GA3 increased both RNA and DNA levels in epicotyls of lentil seedlings.

The objective of the present work was to study the effect of CdCl2 treatment on the level of nucleic acids (DNA and RNA) and on the activity of enzymes (peroxidase and ribonuclease) of Vigna unguiculata roots and shoots at 3 vegetative growth stages, and to investigate the possible alteration in nucleic acid levels and in enzyme activities by the plant growth regulator GA3 after 14 days of CdCl2 and hormone interaction.

Materials and Methods

Plant material and treatments    
Surface sterilized Vigna unguiculata seeds were sown (3 seeds in each pot) in the green house, under natural light conditions at 25-30OC and 50% humidity, in 216 pots(15cm in diameter) containing a mixture of peat moss and sand (1:1), irrigated with distilled water for 15 days. At emergence thinning was done leaving one seedling per pot.The seedlings were then divided into three groups (72 pots each).  Plants of the first, second and third groups were allowed to grow for 15, 30 and 45 days prior to any treatment and were called early, intermediate and late stages, respectively.  The pots of each group were subdivided into two sets.  Pots of the first set were irrigated with distilled water containing 20, 40, 80 and 160 ppm CdCl2, and the pots of the second set were irrigated with the same concentrations of CdCl2, and in addition, 100 ppm GA3 was sprayed on each strategy. [The 100ppm GA3 was selected as the optimal concentration after the preliminary experiments carried out using different levels of the hormone].  The control group was irrigated only with distilled water.  Plants were allowed to grow for a period of two weeks following treatment, after which they were harvested (30, 45, 60 days).Two samples from 8 replicates of shoots and roots during the different stages of development were used to determine the following:
Determination of nucleic acids
Nucleic acids of fresh tissue were extracted with perchloric acid using the procedure described by Malik and Singh [12]. The isolated DNA was determined spectrophotometrically by employing the diphenylamine method described by Schneider [13]. RNA was estimated by orcinol reagent [13].  Calf thymus DNA and yeast RNA were used as standards. 
 
Determination of enzymes
Peroxidases and ribonucleases were extracted according to the method of Nasson [14]. Peroxidase and ribonuclease activities were assayed in roots and shoots according to the method of Malik and Singh [12].

Three samples from 8 replicates of fresh tissue were used for all determinations.

Statistical analysis  
The data (3 replicates) were subjected to analysis of variance using the statistical program Minitab. Means and standard deviations were obtained, and the LSD at p  0.01 and p  0.05 were calculated to compare the significance of the difference in the results between any two groups [15].

Results

The results presented in Tables 1 and 2 showed that CdCl2 (0, 20, 40, 80, 160 ppm) treatment during the early vegetative stage of Vigna unguiculata plants resulted in a gradual dose-related decrease in the levels of DNA and RNA, and the decline was more significant for RNA.  However, this reduction was less significant in plants treated with CdCl2 at the intermediate growth stage, and the minimum decrease in nucleic acid levels was observed when plants were treated with CdCl2 at the late vegetative stage (Tables 1, 2).

The results also showed that the decline in DNA and RNA levels induced by CdCl2 treatment was counteracted by GA3 application, particularly at the lower Cd concentrations (20 and 40 ppm).  The increase in these measures produced by GA3 was most significant when treatment was started at the intermediate stage, followed by the early growth stage.  This increase was more pronounced for DNA compared to RNA.  In addition, Vigna unguiculata roots responded more significantly to CdCl2 treatment and less significantly to the combined treatment of CdCl2 and GA3 (Tables 1, 2).

Tables 3 and 4 present the amount of peroxidase and ribonuclease of Vigna unguiculata roots and shoots in response to CdCl2 treatment.  The results showed that the activities of both enzymes increased by CdCl2 treatment and decreased when the hormone was applied jointly with various concentrations of CdCl2.  Moreover, the response of Vigna unguiculata plants to CdCl2 application in the presence or absence of GA3 on enzyme activity was related to the relative age of the plant and to the concentration of CdCl2 in the growth medium.  The results also revealed that while roots were more affected by CdCl2 treatment, they were less affected by the joint treatment of CdCl2 and GA3 (Tables 3, 4).

Table  1. The effect of various concentrations of CdCl2 in the presence or absence of GA3 on DNA content of Vigna unguiculata L. shoots and roots at the three studied developmental stages
Treatment
(ppm)	DNA (mg/g fresh weight)
(Mean  SD)	
		Shoots	Roots	
Cd	GA3	Early vegetative	Intermediate	Late vegetative	Early vegetative	Intermediate	Late vegetative	
0	0	4.37  0.18	5.61  0.20	6.28  0.18	2.13  0.084	2.79  0.179	3.28  0.188	
20	0	4.14  0.19	5.33  0.17	6.15  0.48	1.98  0.002**	2.53  0.181	3.16  0.166	
20	100	5.19  0.10++	7.17  0.17++	7.41  0.48++	2.44  0.380+	3.24  0.185++	3.64  0.354	
40	0	3.91  0.17**	5.31  0.18	5.97  0.40	1.75  0.004**	2.46  0.177*	3.09  0.183	
40	100	4.58  0.15++	6.38  0.15++	6.93  0.43+	2.13  0.374	2.85  0.202+	3.48  0.380	
80	0	3.21  0.14**	4.83  0.19**	5.88  0.41	1.35  0.005**	2.26  0.123**	2.97  0.155	
80	100	3.49  0.20+	5.68  0.13++	6.48  0.39	1.46  0.265	2.52  0.210	3.21  0.465	
160	0	2.78  0.16**	4.52  0.17**	5.70  0.40	1.08  0.007**	1.93  0.133**	2.89  0.188*	
160	100	2.95  0.08	5.04  0.18++	5.97  0.29	1.10  0.217	2.05  0.174	2.99  0.317	
Cd	LSD at 5%	0.307	0.326	0.707	0.069	0.293	0.322	
	LSD at 1%	0.437	0.465	1.004	0.097	0.416	0.458	
Cd + GA3	LSD at 5%	0.282	0.304	0.754	0.408	0.319	0.540	
	LSD at 1%	0.401	0.432	1.074	0.580	0.454	0.768	
** and * denote significant differences between Cd-treated plants and controls at the 0.01 and 0.05% levels, respectively.
++ and + denote significant differences between plants treated with GA3 + Cd and plants treated with Cd alone at the 0.01 and 0.05% levels, respectively.

Table  2. The effect of various concentrations of CdCl2 in the presence or absence of GA3 on RNA content of Vigna unguiculata L. shoots and roots at the three studied developmental stages
Treatment
(ppm)	DNA (mg/g fresh weight)
(Mean  SD)	
		Shoots	Roots	
Cd	GA3	Early vegetative	Intermediate	Late vegetative	Early vegetative	Intermediate	Late vegetative	
0	0	10.23  1.09	18.15  0.99	22.75  2.07	6.87  0.59	11.70  0.77	16.51  0.87	
20	0	  9.31  0.43   	17.40  0.89	22.04  1.87	5.97  0.12*	10.77  0.86	15.68  0.90	
20	100	12.43  0.59++	24.18  0.18++	26.92  2.73+	7.03  0.39++	13.02  0.07++	17.64  0.88	
40	0	  8.56  0.80*	16.81  0.87+	21.47  2.07	5.14  0.59**	10.32  0.77	15.14  0.98	
40	100	10.57  0.68++	21.65  0.26++	25.54  2.07	5.85  0.32+	11.76  0.17+	16.55  0.92	
80	0	  7.86  0.75**	16.33  0.98*	20.80  2.09	4.76  0.03**	  9.79  0.80*	14.50  1.86	
80	100	  9.13  0.82	19.89  0.28++	23.13  2.07	5.10  0.45	10.66  0.03	15.12  0.80	
160	0	  7.05  1.22**	15.28  1.24**	20.22  2.08	3.28  0.09**	  8.73  0.79**	13.66  0.97*	
160	100	  7.71  0.54	17.16  0.17++	21.96  2.17	3.62  0.47	  9.28  0.03	13.87  1.47	
Cd	LSD at 5%	  1.63 	  1.82	  3.70	0.695	  1.453	2.143	
	LSD at 1%	  2.33	  2.60	  5.27	0.988	  2.067	3.050	
Cd + GA3	LSD at 5%	  1.39	  1.33	  3.92	0.661	  1.043	2.094	
	LSD at 1%	  1.97	  1.89	  5.58	0.940	  1.483	2.980	
** and * denote significant differences between Cd-treated plants and controls at the 0.01 and 0.05% levels, respectively.
++ and + denote significant differences between plants treated with GA3 + Cd and plants treated with Cd alone at the 0.01 and 0.05% levels, respectively.

Treatment 
(ppm)	RNA (mg/g fresh weight)
(Mean  SD)	
	Shoots	Roots	
Cd	GA3	Early vegetative	Intermediate	Late vegetative	Early vegetative	Intermediate	Late vegetative	
0	0	10.23  1.09	18.15  0.99	22.75  2.07	6.87  0.59	11.70  0.77	16.51  0.87	
20	0	9.31  0.43	17.40  0.89	22.04  1.87	5.97  0.12*	10.77  0.86	15.68  0.90	
20	100	12.43  0.59++	24.18  0.18++	26.92  2.73+	7.03  0.39++	13.02  0.07++	17.64  0.88	
40	0	8.56  0.80*	16.81  0.87+	21.47  2.07	5.14  0.59**	10.32  0.77	15.14  0.98	
40	100	10.57  0.68++	21.65  0.26++	25.54  2.07	5.85  0.32+	11.76  0.17+	16.55  0.92	
80	0	7.86  0.75**	16.33  0.98*	20.80  2.09	4.76  0.03**	9.79  0.80*	14.50  1.86	
80	100	9.13  0.82	19.89  0.28++	23.13  2.07	5.10  0.45	10.66  0.03	15.12  0.80	
160	0	7.05  1.22**	15.28  1.24**	20.22  2.08	3.28  0.09**	8.73  0.79**	13.66  0.97*	
160	100	7.71  0.54	17.16  0.17++	21.96  2.17	3.62  0.47	9.28  0.03	13.87  1.47	
Cd	LSD at 5%	1.63	1.82	3.70	0.695	1.453	2.143	
	LSD at 1%	2.33	2.60	5.27	0.988	2.067	3.050	
Cd
+
GA3	LSD at 5%	1.39	1.33	3.92	0.661	1.043	2.094	
	LSD at 1%	1.97	1.89	5.58	0.940	1.483	2.980	
** and * denote significant differences between Cd-treated plants and controls at the 0.01 and 0.05% levels, respectively.
++ and + denote significant differences between plants treated with GA3 + Cd and plants treated with Cd alone at the 0.01 and 0.05% levels, respectively
Table 3. The effect of various concentrations of CdCl2 in the presence or absence of GA3 on peroxidase activity of Vigna unguiculata L. shoots and roots at the three studied developmental stages
Treatment
(ppm)	DNA (mg/g fresh weight)
(Mean  SD)	
		Shoots	Roots	
Cd	GA3	Early vegetative	Intermediate	Late vegetative	Early vegetative	Intermediate	Late vegetative	
0	0	10.48  1.11	7.37  0.57	6.36  1.08	12.26  1.01	8.76  1.37	7.82  0.83	
20	0	12.35  1.01	8.44  0.34	6.95  1.16	15.75  1.25*	10.65  1.40	8.90  1.17	
20	100	9.92  0.25++	6.72  0.28++	5.89  0.19	13.42  0.43+	8.32  0.09+	8.05  0.14	
40	0	13.62  1.23**	8.95  0.80*	7.41  1.04	18.37  1.35**	11.10  0.96	9.54  1.24	
40	100	11.53  0.27+	7.29  0.04++	6.34  0.187	16.27  0.62	8.82  0.06+	8.79  0.10	
80	0	16.58  1.18**	9.72  0.50**	7.86  1.18	21.19  1.88**	12.68  1.48**	10.36  1.15*	
80	100	14.92  0.18+	8.26  0.06++	7.14  0.31	19.33  0.72	11.29  0.08	9.85  0.48	
160	0	20.95  1.29**	10.98  0.78**	8.50  1.09*	27.92  1.99**	14.24  1.30**	11.20  1.18**	
160	100	19.44  0.20	9.64  0.05++	7.82  0.06	26.44  0.34	13.15  0.03	10.87  0.58	
Cd	LSD at 5%	  2.14	1.13	2.02	  2.14	  2.38	  2.05	
	LSD at 1%	  3.04	1.61	2.87	  3.04	  3.39	  2.91	
Cd + GA3	LSD at 5%	  1.55	0.85	1.46	  1.55	  1.67	  1.60	
	LSD at 1%	  2.20	1.20	2.08	  2.20	  2.38	  2.28	
** and * denote significant differences between Cd-treated plants and controls at the 0.01 and 0.05% levels, respectively.
++ and + denote significant differences between plants treated with GA3 + Cd and plants

Table 4. The effect of various concentrations of CdCl2 in the presence or absence of GA3 on ribonuclease activity of Vigna unguiculata L. shoots and roots at the three studied developmental stages
Treatment
(ppm)	DNA (mg/g fresh weight)
(Mean  SD)	
		Shoots	Roots	
Cd	GA3	Early vegetative	Intermediate	Late vegetative	Early vegetative	Intermediate	Late vegetative	
0	0	53.73  4.69	42.47  3.41	38.17  3.77	61.14  5.23	49.09  5.32	44.59  3.21	
20	0	59.31  3.09	45.28  1.65	40.03  3.67	72.84  5.75*	54.67  5.26	48.22  4.92	
20	100	50.37  4.42+	32.56  2.26++	34.45  0.17+	61.97  5.34+	43.49  0.18++	43.03  1.73	
40	0	63.57  3.45**	47.02  3.73	41.87  3.69	79.22  5.18**	58.32  6.22	50.28  6.28	
40	100	55.11  4.43+	35.68  2.69++	36.99  0.95+	69.85  4.28	48.21  0.44+	46.51  1.43	
80	0	70.21  2.64**	50.28  1.76**	42.92  3.83	88.96  5.40**	63.42  6.25*	53.61  6.16	
80	100	63.48  4.73+	42.20  2.92++	39.33  0.41	81.13  6.25	55.12  0.21+	50.57  1.50	
160	0	81.82  3.42**	55.30  1.66**	43.48  3.66	101.08  5.11**	69.13  6.03**	58.09  5.34*	
160	100	75.43  2.89	47.41  1.54++	40.81  0.75	95.51  5.72	63.34  0.31	56.28  1.84	
Cd	LSD at 5%	  6.40	  4.74	 6.78	  9.71    	  10.60	    9.64   	
	LSD at 1%	  9.11	  6.75	 9.64	13.81	  15.08	  13.71	
Cd + GA3	LSD at 5%	  6.74	  4.34	4.84	  9.82         	    7.66	    7.63	
	LSD at 1%	  9.59	  6.18	6.88	13.97	  10.90	  10.85	
** and * denote significant differences between Cd-treated plants and controls at the 0.01 and 0.05% levels, respectively.
++ and + denote significant differences between plants treated with GA3 + Cd and plants treated with Cd alone at the 0.01 and 0.05% levels, respectively.

Discussion

Nucleic acid levels of Vigna unguiculata roots and shoots decreased in the presence of CdCl2, a trend which was more significant at higher CdCl2 concentrations and during the early growth stage, and becomes less significant with further development.  Furthermore, the decline in these measures was relatively more in roots than in shoots.  Reduction in nucleic acid content of Arachis hypogea under high CdCl2 levels (500µM) was reported earlier by Satakopan and Rajendran [16], who attributed the decline to the heavy metal interference with the biosynthesis of DNA and RNA. The observed reduction in RNA of Vigna unguiculata shoots and roots could probably be due to the intensified activity of ribonuclease.  This suggestion was supported by the present increase in this measure induced by CdCl2 treatment.  Bhattacharyya and Choudhuri [17] reported a decline in protein and RNA levels with a corresponding rise in the activity of hydrolytic enzymes, protease and ribonuclease, which suggests the promotion of catabolic activities caused by CdCl2 and PbCl2.  Thus, it may be assumed that imposition of Cd stress induced early senescence in Vigna unguiculata seedlings through enhancement of degradation of the metabolites such as chlorophyll, protein and RNA, particularly during the early vegetative stage and at higher CdCl2 concentrations.  Reduction in chlorophyll and proteins of terrestrial Vigna and Aquatic Hydrilla by CdCl2 and PbCl2 treatments was reported by Bhattacharyya and Choudhuri[17]. On the other hand, the decline in DNA level seems to result from Cd interference with the process of cell division, thus decreasing the number of cells per unit weight. This suggestion confirms the finding of Falchuck et al. [18] who indicated that Cd inhibited cell division in Euglena gracilis, presumably by disrupting the process critical to karyokinesis.

The results of this study also indicate a variable degree of stimulation in DNA and RNA levels of Vigna unguiculata shoots and roots when GA3 was applied with various concentrations of CdCl2. This increase was more significant at lower Cd doses (20 and 40 ppm) and during the intermediate stage, followed by the early growth stage.  Enhancement of DNA and RNA levels by GA3 was reported by Hamed et al. [19], who showed that pre-soaking Fenugreek, Trigonella foenum-graecum, plants in GA3 improved the lowering of protein, RNA and DNA levels that was induced by water-stress.  The increase in DNA and RNA levels in roots and shoots of Vigna unguiculata seedlings seen in the present study in response to GA3 treatment is possibly related to the hormone role in promoting the onset of DNA and RNA synthesis.  Key [20] indicated that the maintenance of a high RNA content of GA3-treated tissues correlates with high synthetic rate. Nitsan and Lang[11] observed growth stimulation paralleled with an increase in nucleic acid levels in the presence of GA3. Gibberellic acid has been proposed to cause an increase in growth by acting at the level of DNA replication [11], transcription [10] or translation [21].

The results of the present study also revealed an increase in the activities of peroxidase and ribonuclease in the presence of CdCl2. This stimulation was more significant at higher CdCl2 concentrations and during the early vegetative stage, and decreased with further development.  Bhattacharyya and Choudhuri [17] observed enhanced protease and ribonuclease activities with a concomitant decline in protein and RNA levels of Vigna catjang plants in response to CdCl2 and PbCl2 treatments.  Reduction in proteins of Cajanus cajan plants by CdCl2 treatment was observed by Sheoran etal[22].  Thus, the decline in protein and RNA contents with the corresponding rise in the activity of hydrolytic enzymes due to CdCl2 stress strongly suggests the promotion of catabolic activities.  Mohan and Hossetti [7] also attributed the increase in peroxidase activity in the presence of CdCl2 to senescence of Lemna plants, which was demonstrated by the increase in the production of secondary metabolites like hydrogen peroxides, thiols, phenols, etc. On the other hand, Van Assche and Clijsters [6] attributed enzyme induction to the increase of de novo protein synthesis, or to the activation of enzymes already present. 
 
The results of this study also revealed that the induction of peroxidase and ribonuclease activities caused by CdCl2 at the various studied phenological stages was lowered to different degrees by GA3 application, particularly at 20 and 40 ppm CdCl2 concentrations and during the intermediate growth stage of Vigna unguiculata plants.  These results are in accordance with those of McCune and Galston [23] who reported that application of GA3 to the dwarf strains of pea, Pisum sativum L., and Corn, Zea mays L., plants increased the growth rate and decreased the peroxidase activity of the dwarfs. A stimulation in growth of Vigna unguiculata plants by GA3 was reported by Al-Rumaih [24], and the decrease in peroxidase activity observed in the present study seems to parallel this increase.  Halevy [25] showed hypocotyl growth stimulation of cucumber, Cucumis sativus L. with a simultaneous inhibition of peroxidase and IAA-oxidase activities in response to GA3 treatment.  Such a correlation was explained by Galston [26] who attributed the decline in peroxidase activity in the presence of GA3 to the hormone role in inhibiting the auxin oxidase inhibitor, the enzyme responsible for the destruction of indole acetic acid (IAA), consequently increasing the IAA level, which in turn stimulate growth.

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التأثير التفاعلي لكلوريد الكادميوم وحمض الجبريليك على محتوى الأحماض النووية ونشاط 
بعض الإنزيمات في نبات اللوبيا Vigna unguiculata

*منى محمد الرميح، *شهيرة صالح رشدي،** ارجومند سلطان وارسي.
*قسم النبات والأحياء الدقيقة، و **قسم الكيمياء الحيوية، كلية العلوم، جامعة الملك سعود؛
ص.ب 2455؛ الرياض 11451؛ المملكة العربية السعودية.
(قدّم للنشر في 25/3/1422هـ؛ وقبل للنشر في 28/3/1423هـ)

ملخص البحث : تم دراسة تأثير تركيزات مختلفة ( صفر ، 20 ، 40 ، 80 ، 160 جزء في المليون ) من  كلوريد الكادميوم ( CdCl2 ) في  وجود أو غياب 100 جزء  في المليون من هرمون حمض الجبريليك ( GA3 ) عـلـى محتـويات الأحـمـاض النــوويـة ( DNA,RNA ) ونشـاط الإنزيمات ( بيروكسيديز و رايبونيوكلييز ) في المجموع الخضري والجذري لنبات اللوبيا Vigna unguiculata  وذلك في ثلاث مراحل من النمو ( مبكرة ، متوسطة ، متأخرة ) . أوضحت النتائج انخفاض  محتويات  الأحماض النووية  وارتفاع نشاط  الأنزيمات في  وجود كلوريد الكادميوم ، وكانت هذه التغييرات أكثر معنوية في تركيزات كلوريد الكادميوم  المرتفعة وخلال مرحلة النمو الأولى ، واقل معنوية في مرحلة النمو الخضري المتأخرة .
إضافة  حمض الجبريليك إلى التركيزات المختلفة من كلوريد الكادميوم أدت إلى زيادة محتوى الأحماض النووية وإلى انخفاض نشاط الإنزيمات بدرجات متفاوتة خاصة عند التراكيز المنخفضة لكلوريد الكادميوم وأثناء المرحلة المتوسطة وتلتها المرحلة المبكرة ، دالاً بذلك على دور حمض الجبريليك في تخفيض التأثير المثبط لكلوريد الكادميوم . وقد كان المجموع الجذري أكثر تأثر بمعاملات كلوريد الكادميوم وأقل تأثر بالمعاملة المزدوجة لكلوريد الكادميوم وحمض الجبريليك مقارنة بالمجموع الخضري .