RESPONSE OF Citrullus colocynthis L. TO SINGLE AND COMBINED STRESSES OF SALINITY (NaCl) AND HEAVY METAL (NiCl 2 )

Salinity and heavy metal stresses are great hindrances to germination and the early developmentof plants. Nickel (Ni) is an indispensable micronutrient for plants at low while toxic in highconcentrations. Citrullus colocynth L. is a medicinal cucurbit weed in desert and agriculturalareas. Germination and early development of seedlings determine the future of the plant. Thecontemporary target of the study is to appraise the influence of single and combined stresses byvarying concentrations of NaCl and NiCl 2 on germination and seedlings of C. colocynth.Germination percentage, radicle length, plumule length, fresh weight and dry weight of seedlingsof C. colocynth with three levels of salt (100mM, 200mM and 400mMNaCl), three levels ofheavy metal (50, 100, 200uMNiCl 2 ) and Nine combined levels(100mMNaCl +50uM NiCl 2 ),(200mMNaCl +50 uMNiCl 2 ) (400mMNaCl +50uM NiCl 2 ) (100mMNaCl +100uMNiCl 2 )(200mM NaCl +100uM NiCl 2 ) (400mMNaCl +100uMNiCl 2 ) (100mMNaCl +200uMNiCl 2 )(200mMNaCl +200 uMNiCl 2 ) (400mMNaCl +200uMNiCl 2 ) were studied. This experiment wasconceded out in a completely randomized design with four replications. The responses showedan adverse trend with increasing stress levels. Germination and seedling growth factors declinedunder high-stress levels of salt (400mM NaCl), high HM (200 uM NiCl 2 ), and combined highsalt or high HM but positively improved on lower salt(100mMNaCl), lower HM (50uMNiCl 2 )and combined lower salt with lower HM (100mMNaCl+50uMNiCl 2 ).