We thank you for your comment, but maybe you made a mistake asking here. If these are published papers you require, I suggest you email the author directly. If you are having difficulty, send full details of the papers and we will try and help. I searched for two of the titles you mention, and could not find them.

1- . The effect of drought on physiological characteristics, amount of proline and soluble sugars in two sweet potatoes (Ipomoea batatas) cultivars conditions of tissue culture.

2- Effect of water stress induced by solid medium of poly ethylene glycol (PEG 6000)
on the seedling characteristics of sweet potato.
3- study of drought stress effects in differens growth stages on sweet potato cultivars.

and other reprints on the subject.

With many thanks , yours sincerely

Department of
Fars Science and Research Branch
Islamic Azad University
P.O.Box : 73715-181
Fars Province, Marvdasht, IRAN