EFFECT OF NACL SALINITY ON GROWTH AND DEVELOPMENT OF JOJOBA CLONES .1. YOUNG PLANTS

Young jojoba (Simmondsia chinensis) plants of four high-yielding commercial clones grown in sand culture were irrigated over a period of 11/2 years with nutrient solutions having EC values of 2, 4, 8, and 12 dS m-1 (corresponding to addition of 0, 20, 60, and 100 mole m-3 NaCl). All clones with the exception of clone 64, the best producer among Israeli selections in the absence of salt stress, developed reasonably well up to 8 dS m-1, growth parameters such as shoot elongation and node production remaining unaffected. At 12 dS m-1 all clones showed signs of salinity stress, clone 154 proving most tolerant and clone 64 most sensitive. Exposure to 12 dS m-1 reduced the number of viable flower buds in three of the four clones, clone 64 being most affected. Although clone 64 produced the highest number of flower buds at 2 and 4 dS m-1, clone 154 performed best at 12 dS m-1, with twice the number of viable flower buds. In all clones a high percentage of flower buds wilted or degenerated at the highest salinity level. Salinity treatments increased both leaf thickness and succulence. Unlike many other perennial woody plants, jojoba does not exclude Na and Cl ions from leaves, but rather accumulates them in high concentrations in mature leaves. The most sensitive clone, 64, accumulated the highest amount of Na and Cl ions. Potassium content was only slightly affected by salinity, and at 12 dS m-1 its content in mature leaves and roots decreased by about 30 % compared with that of control plants. Salinity inhibited net photosynthesis during part of the day, presumably due to the steeper decline in water potential in the saline-treated plants.