Studies on Calcium Absorption in Vegetable Crops

The most important purpose of the study was to clarify the effects of flowering and fruiting on calcium absorption in both the vegetative and reproductive phases of some vegetable crops. Two groups of vegetables, fruit vegetables of tropical origin and leaf vegetables of temperate origin, were tested. In the tropical category, tomato and eggplant, and in the temperate category, Chinese head in cabbage and head head lettuce were included, respectively.The results are summarized as follows:1. In comparison with the vegetative phase, the reproductive phase displayed a higher percentage of calcium content in the leaves of vegetable crops. In tomato and eggplant, the content of calcium in leaves increased in proportion to the number of fruit set, and decreased after the fruit was harvested. Thus it was found that a cyclic change in calcium content occurred in parallel with growth cycle of the plants. As both Chinese head cabbage and head lettuce have only one cyclic growth, the increase in the calcium content of the leaves for these crops was due to the process of flowering.2. In the reproductive phase of tomato and Chinese head cabbage, increases of water soluble calcium (water soluble organic acid salt and inorganic compound) and hydrochloric acid soluble calcium (oxalate calcium) were found in leaves, and these phenomena were more evident in the leaves of tomato which were nearest to the first fruit cluster. Moreover, oxalic acid and citric acid in leaves accumulated at a higher rate in flowered or fruited plants than in deflorated or head formed plants. Thus it was clearly recognized that an increase in the content of calcium influenced by organic acid in leaves was shown in flowered or fruited plants.3. In tomato, the content of potassium and magnesium in leaves indicated a noticeable decrease in fruiting plants, and phosphorus showed a slight increase in leaves due to fruiting.4. In Chinese head cabbage, the content of nitrogen, phosphorus and potassium in leaves was not effected by the flowering and head forming of the plants.5. In tomato and Chinese head cabbage, a quantitative balance between total cation (K, Ca, Mg and Na) and total anion (inorganic acid and organic acid) was found in leaves.