THE CONTROL OF SHOOT-TIP NECROSIS IN PISTACIA-VERA L IN-VITRO

The effect of increased concentrations of calcium (Ca) (3-24 mM) and b oron (B) (100-800 mu M) in the medium was studied on the occurrence of shoot tip necrosis (STN) in cultures of Pistacia vera L. STN was sign ificantly reduced by application of Ca or B, however media with more t han 200 mu M boron had reduced shoot multiplication. Ca (12-24 mM) sup plied as calcium chloride reduced STN without any adverse effect on sh oot multiplication or elongation, whereas calcium acetate reduced elon gation. It is concluded that STN is a physiological mineral disorder a ssociated with Ca and/or B deficiency in the meristematic regions of a ctively growing shoots. Application of Ca (up to 24 mM) as calcium chl oride to the medium was the best treatment for the control of STN. Red uction of humidity or increased aeration in the culture jars did not h ave any significant effect on the occurrence of STN.