| Abstract: | Two peach rootstocks, Nemaguard and Lovell, were subjected to 0, 25, 50, 75, 100, and 125 ppm Al in sand culture. Aluminum toxicity caused Fe chlorosis, tip dieback and small distorted leaves. Roots were necrotic, misshapen, and lacked fine branches. Shoot and root dry weights were reduced. Aluminum reduced shoot Ca, Mo, Zn, Cu and Fe, but K, Mg and Mn were unaffected. Root Ca, Mo, K, Mg, and Zn were reduced. In a factorial experiment with peach seedlings using 0, 50, and 100 ppm Al and 0, 50, and 100 ppm Ca, Ca alleviated Al toxicity at 50 ppm Al by reducing Al accumulation. Calcium levels had no effect at 0 and 100 ppm Al. Aluminum decreased shoot and root growth and shoot Ca content. Prunus tomentosa, P. cerasifera (Myrobalan), P. besseyi, P. insititia, and P. persica Nemaguard, Lovell and Nemared were subjected to 0, 50, and 100 ppm Al in sand culture. Prunus tomentosa was the most sensitive to Al toxicity based on reduction in shoot and root weight. Prunus besseyi was least affected. The others were intermediate in their response. Prunus tomentosa and Nemaguard had higher shoot Al content at 50 ppm Al level than others. Adjusting soil pH from 4.9 to 4.0 caused a decrease in growth of peach seedlings and increased shoot Mn and Al content. Liming the soil to 6.3 had no effect on growth. This was probably because the soil was incubated with CaCO₃ for too short a period of time (3 weeks). A follow up study using Ca(OH₂) as a liming material in soil pot culture identified P. salicina as least sensitive to acid soil and P. tomentosa, and P. persica Nemaguard as most sensitive. While P. cerasifera, P. mexicana and P. maritima were intermediate. In hydroponic studies using Mn levels of 4.5, 15, 30 and 45 ppm, Mn caused Fe deficiency, leaf crinkling and marginal necrosis in peach seedlings. No differences were observed in Mn tolerance or Mn content between P. tomentosa, P. maritima, P. besseyi, P. minutiflora, P. salicina, and P. persica Nemaguard. |
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