Answer: Calcium (Ca) is needed for cell walls, cell growth and division; nitrogen assimilation. It is also a Cofactor for enzymes.
Calcium deficiencies in the tomato plants first appear at the terminal growing point, the newest growth. Underdeveloped leaves exhibit yellowing between the veins and browning of the tissues at the leaf's margins. Symptoms show up in the newest growth because Ca is dependent on an active transpriational flow, so it moves to the older larger leaves with more surface area available for transpiration. Once Ca is deposited, most of it is incorporated into insoluble organic compounds; thus, transpiration to the younger leaves is negilible. This is just the reverse case as with N, P and K which can be translocated to the new growth at the expense of the old.
Like the newer undeveloped leaves, fruits have lower transpiration rates; accordingly it is susceptible to calcium deficiencies which manifest itself as blossom-end rot. Conditons in soils (or growing media) which restrict Ca, even when Ca is adequately present, are high concentrations of competing cations [+] such as NH4+ (ammonium sources of N), K and Mg (magnesium), salinty, low temperature, dry soil, and high humidity.
Q&A Library Searching Tips