So if water is not being lost from the leaves, as happens for example in an atmosphere of high humidity, tissues can become deficient in these elements.
When a deficiency of either calcium or boron is suspected, it can be difficult to decide which element is actually causing the problem. In the experiments discussed here, seeds of pansy, Petunia and Gerbera were germinated in moist Oasis foam in small, open-ended tubes. The tubes were then supported within larger containers containing either a complete nutrient solution or one lacking either calcium or boron.
In other experiments, the plants were grown in a complete nutrient solution and then exposed for just six days to a solution lacking either calcium or boron.
Plants of pansy, Petunia and Gerbera that experienced calcium deficiency were smaller than control plants and exhibited discolouration and eventually necrosis of their younger leaves. Plants that experienced boron deficiency rarely showed necrosis but the newest growth was usually distorted. These distinctive symptoms appeared even when the relevant nutrient was withheld for just six days.
Characterization of Calcium and Boron Deficiency and the Effects of Temporal Disruption of Calcium and Boron Supply on Pansy, Petunia, and Gerbera Plugs by Krug, Whipker, Frantz and McCall (2009). HortScience 44 (6): 1566-1572. Members of ISHS can view HortScience from the website www.ishs.org.