NUTRIENT LEVELS IN CACTI—RELATION TO NOCTURNAL ACID ACCUMULATION AND GROWTH

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Abstract
The levels of ten essential nutrients and Na in the chlorenchyma and subjacent parenchyma of ten species of cacti were measured along with the maximal rates of nocturnal acid accumulation. Nutrient levels varied considerably among species; also, soil differences between sites affected levels within Opuntia ficus‐indica and O. chlorotica. Compared to most agronomic plants, chlorenchyma levels of Ca, Mg, and Mn in cacti tended to be higher and Na lower. Moreover, Ca tended to accumulate in the chlorenchyma with age. The strongest correlation between nutrient level and a metabolic process for the 11 elements tested was with N, where nocturnal acid accumulation tended to be greater when the N level in the chlorenchyma was higher (r2 = 0.39). Hydroponically grown seedlings of Carnegiea gigantea, Ferocactus acanthodes, and Trichocereus chilensis responded to N fertilization, reaching about 90% of their maximal growth rates when provided with N at 0.25 x that in Hoagland's solution (namely, 4 mm nitrate). Nocturnal acid accumulation was negatively correlated with the chlorenchyma Na (r2 = 0.32), which averaged only 28 ppm for O. ficus‐indica (the root contained considerably more) and 234 ppm for the other species. Growth of seedlings was 50% reduced at about 100 mm NaCl for F. acanthodes, T. chilensis, and C. gigantea, while variations in P had a relatively small effect.
Funding Information
  • Department of Energy (DE-AM03-76-SF00012)