Effect of temporary calcium deficiency on tomato growth and mineral nutrition

The effects of temporary calcium deficiency on the growth and mineral nutrition of whole tomato (Lycopersicon esculentum All. cv. Rondello) plants were investigated at the 22-23 leaf stage. Three deficiency period durations (5, 8 and 10 days or -Ca5, -Ca8, and -Ca10, respectively) were tested during the two series of hydroponic experiments in a greenhouse. At the end of the calcium deficiency period, the plants were supplied again with a standard nutrient solution. In the plants subjected to a 5-day calcium deficiency, stem growth and new leaf formation were slowed 10-12 days after the onset of the treatment. The effect was rapidly attenuated and no visual symptom was observed thereafter. The stem growth slow-down induced by treatments -Ca8 and -Ca10 8-10 days after the onset of calcium deficiency was followed by the rapid appearance of visual symptoms and by the death of the apical meristem. Thus, beyond five days, even though the plant was supplied again with calcium, the appearance of visual symptoms shortly preceded the total necrosis of the apical meristem of the stem. Two major phenomena were characterized by the analysis of plant uptake and contents. The calcium deficiency showed the occurrence of a strong calcium-magnesium antagonism mainly localized in the leaves, which suggests the influence of calcium on magnesium translocation to the above-ground parts. Besides, in the absence of calcium in the nutrient solution, phosphorus uptake was decreased as shown by the decreased root content. The phenomenon might be related to the occurrence of precipitated dicalcium phosphate at the root surface. The precipitate was likely to constitute a calcium reserve which was rapidly depleted by the plant after a 5-day deficiency.