Influence of soil and mineral stresses on cacti

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Abstract
The influence of five soil and mineral stresses found in arid regions on growth and nutrient status were examined for two cactus species, Ferocactus acanthodes and Opuntia ficus‐indica. The plants were raised in sand culture in a glasshouse for 6 months with a range of treatment levels of salinity (NaCl), B, heavy metals (Cu and Zn). Ca, and pH. Roots of both plants were sensitive to salinity (stress shown at 25 mM NaCl), but only O. ficus‐indica showed shoot growth inhibition at this level. For O. ficus‐indica Na accumulation occurred in the root system with only limited translocation to the shoot, while for F. acanthodes Na was readily translocated to the shoots where it accumulated. In the B treatments, O. ficus‐indica showed typical visual symptoms of B toxicity along with high B accumulation in its photosynthetic stem. Although the root growth of both species was slightly affected by Cu and Zn at concentrations 20 times those in Hoagland solution, shoot growth was not substantially inhibited until concentrations were 1000 times greater. Neither species required high soil Ca levels and they were essentially uninfluenced from pH 4.5 to 8.5. Thus, O. ficus‐indica is more sensitive to salinity, B, and heavy metal stresses than F. acanthodes. Of the five soil and mineral stresses considered here, only their low tolerance to salinity and limited tolerance to B might limit their distribution or cultivation in arid regions.