PHYLLOCLADE MORPHOLOGY RELATED TO SALT LEVELS IN ITALIAN RUSCUS (DANAE RACEMOSA)

          Plants of Danae racemosa were grown in pots containing sand under 70% shading. They were fed every 4-7 days for 16 months with volumes of nutrient solutions sufficient to wash the substrate and to maintain fixed E.C. values. Different E.C. levels (2.0 - 3.0 - 4.0 - 5.0 mS/cm) with constant N:P:K:Ca:Mg ratio were determined in the nutritive solutions by appropriate amounts of fertilizers. Plant growth was monitored and biometric characters related to phylloclades were evaluated. A detrimental effect of E.C. levels of the nutritive solutions higher than 3.0 mS/cm on plant growth (fresh weight, number of aerial branches) was pointed out. The E.C. of the nutritive solution affected the biometric characters of the phylloclades. An E.C. level higher than 3.0 mS/cm, induced a reduction of phylloclade length, breadth and area. The length/maximum breadth ratio particularly increased with increasing E.C. of the nutrient solution from 2.0 up to 5.0 mS/cm. The changes in length/maximum breadth ratio dramatic affected the phylloclade morphology determining a lanceolate shape. Such modifications in high salinity substrate conditions were displayed by the upper phylloclades of the aerial branch. No injury symptoms (chlorosis, burn, necrosis etc.) were detected; nevertheless the changes in phylloclade shape affect the commercial quality of Danae racemosa, a cut foliage crop widely grown in Italy and important from an economic point of view. The use of such leaf parameters for diagnostic purpose is discussed.

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