ADAPTATION OF 5 COLUMNAR CACTUS SPECIES TO VARIOUS CONDITIONS IN THE NEGEV DESERT OF ISRAEL

Five species of columnar cati were examined with the aim of introducin g new orchard crops to the Negev desert of Israel. The species compris ed Stenocereus gummosus, S. griseus, S. thurberi and Pachycereus pring lei, all found in semi-arid regions of Mexico, and Cereus peruvianus, which is grown in sub-tropical regions. Young seedlings were planted a t four sites in the Negev. The sites differ in climatic conditions and water quality Growth data, expressed as total stem length and stem bi omass, was obtained after five to six years in the orchards. They show ed that C. peruvianus grew best in the site with moderate temperatures and good-quality water, whereas the other species also did well under more extreme conditions of high temperatures and brackish water. Grow th of all species was significantly retarded at the site having water with the highest NaCl content. In the sixth year a severe drop in temp erature at one of the sites caused extensive injury to C. peruvianus a nd S. griseus plants, raising doubts as to the suitability of that sit e for their cultivation. At this stage C. peruvianus is the most promi sing candidate for domestication. Its growth rate was much higher than that of the other species, yield was precocious and fruit of good qua lity. Stem tissue ion concentrations (dry weight basis) showed that ac cumulation of K+ was similar at all four sites and that Na+ and Cl- we re significantly higher (probably in toxic concentrations) at the site with the highest concentrations of Na+ and Cl- ions in the water. At all sites Cl- concentration in C. peruvianus was much lower than that in the other species indicating that the exclusion of Cl- from the ste ms was not correlated to salt tolerance.