Reasons of leaves withering in tropical plants cultivated under greenhouse conditions

In order to determine the reasons of necrosis of exotic plants leaves cultivated in greenhouses plants belonging to ten following species were examined: Ceratozamia mexicana Brongn., Stangeria eriopus (Kunze) Nash (Cycadaceae), Eriobotrya japonica Lindl. (Rosaceae), Camellia japonica L. (Theaceae), Phoenix roebeleni O'Brien (Palmae), Sequoia sempervirens Endl. (Taxodiaceae), Calathea bachemiana Morr. (Marantaceae), Cordyline terminalis Kunth (Agavaceae), Spathiphyllum wallisii Reg. and Anthurium magnificum Lind. (Araceae). Chemical analysis were performed in soil samples in which these plants grow, in samples of tap-water applied for watering and in samples of decaying and healthy leaves. In order to examine the process of withdrawal of mineral components from necrotic leaves, both: necrotic and green parts of decaying leaves were subjected to examination. On the basis of the research it was concluded, that - in spite of generally low level of salinity of the water used for watering - some ions content, particularity that of CI-, was unfavourable to plants. Unfavourable ionic composition was discovered in water extracts derived from some of the breeding-ground soils. A comparison of healthy and decaying, necrotic leaves chemism proves that CI- assimilated by the plants from the breeding-grounds and accumulated in leaves, affects them toxically.