Plants need a wide range of nutrients for their proper growth, and tomatoes are no exception
Tomatoes, like other plants, are susceptible to nutritional disorders, which can result in discoloration, poor appearance, diminished quality, and decreased production yields. Logically, an insufficient supply of nutrients can cause a nutritional disorder. Yet an unchecked, excess application of nutrients can actually be just as harmful (or even more so). We thus offer the following analysis of the principal nutrients needed for tomatoes, along with the symptoms and consequences of either a deficient or excess supply.
- Deficiency: Lack of vigor in the plant, with thin stalks and rigid petioles. The leaves become pale green, yellow, or even reddish, and fall prematurely. Mature leaves are the first to so discolor, and do so uniformly, while new leaves fade and are smaller. Fruits are of lower caliber.
- Excess: Stimulation of vegetative growth and falling of flowers. Maturation is irregular and reduces production yields. This can also lead to Potassium or Magnesium deficiencies (as we shall see below).
- Deficiency: During a fruit’s seed setting phase, demand for potassium increases. Insufficient potassium is thus a common deficiency, marked by a yellowing of leaf edges. The yellowing is first seen in the most mature leaves. Later, the leaves curve upward, due to necrosis along their edges. Leaf nerves may take on a brownish-gray coloration. The fruit displays several physiological disorders, since this deficiency provokes an irregular maturation on the fruit’s surface, for instance, the appearance of a yellowish star-shaped spot at the fruit apex.
- Excess: Blocks elements such as zinc, iron, magnesium, and manganese.
- Deficiency: Interveinal chlorosis on the most mature leaves, gradually extending to the younger leaves. Yellowish or orangish tone at the center of the leaves. In the fruit, a lack of balance between calcium and magnesium provokes a physiological disorder named Tip.
- Excess: At high levels, magnesium competes with calcium and potassium for absorption by the plant, and could thus cause a deficiency of those elements in the leaf tissue.
- Deficiency: Lack of vigor in the plant. A necrosis appears on the edges of young leaves, which curve into a spoon shape. The most common symptom is rotting of the fruit at its apex.
- Excess: An excess of calcium can be just as harmful as a calcium deficiency. Consequences of excess calcium include stunted growth of the plant, and deficiencies of boron, magnesium, zinc, manganese, or copper.
- Deficiency: Mature leaves take on a purplish tone in their interveinal spaces and on the leaf backs. The plant displays a loss of vigor and takes on a stunted appearance, with curving of the stalk. The plant also grows slowly, with a delay in the maturation phase.
- Excess: Blocks elements such as iron, zinc, or copper.
- Deficiency: General Chlorosis. Curling of the leaves and appearance of interveinal specks on the most mature leaves. Those leaves become thicker, with a concave curvature. A molybdenum deficiency tends to indirectly produce a nitrogen deficiency, since it interferes, causing the mineral nitrogen that the plant absorbs to transform into organic nitrogen.
- Excess: An excess of molybdenum can provoke copper and iron deficiencies.
- Deficiency: Interveinal spots on the young leaves, which later undergo necrosis. Reduced flowering.
- Excess: Necrotic brownish-gray spots on leaves, petioles, and shoots, starting on mature leaves and progressing to the younger ones. In addition, the leaves become spoon shaped, similar to what is seen with a calcium deficiency. There is a darkening of the roots, which sometimes become brittle.
- Deficiency: The leaves display a slight chlorosis with purple tones and later undergo necrosis at their apex. The tomato becomes rough and cork-like in texture, with zones that are excessively watery and sunken, provoking an early maturation.
- Excess: Visible signs appear on the mature leaves, which take on a yellowish characteristic at their tips. This chlorosis spreads, imparting an orangish-yellow coloration to the leaf edges and between the nerves. Later, the edges undergo necrosis. In acute cases, there is a major loss of leaves or even death of the plant.
Cell Wall Calcium
AGQ Labs has developed a state-of-the-art analysis of the Cell Wall Calcium fraction in fruit, a good tool for diagnosing alterations in pre- and post-harvest quality.
It is well known that post-harvest is a key period with a direct influence on the quality and appearance with which fruits and vegetables reach their point of sale. Even if we have done a superb job in the field, if the product does not successfully endure the period between harvest and sale, we will have failed.
Several factors have a bearing in this process. One factor with a major role is tissue calcium content. Calcium’s structural function is directly related to plant tissue stability and thus to the product’s post-harvest behavior (rotting, brown spots, loss of consistency, etc.), as well as its probability of being affected by pre-harvest damage (creasing in citrus fruit, cracking in stone fruits, bitter pit in apples, etc.).
In addition to having a structural function (for cell wall bound calcium in the form of calcium pectates), calcium is involved in other functions in plant cells. It is thus also found in other plant parts, as soluble calcium in the apoplast and symplast (in the form of nitrates, chlorides and amino acids), insoluble calcium in form of precipitates in the vacuoles (mainly in the form of phosphates, carbonates and oxalates) and residual calcium in highly insoluble forms (mainly).
Cell Wall Calcium is a diagnostic tool for evaluating quality parameters related to the appearance and market life of the product. And in certain matrices, total calcium, with quantification limits adapted to the fruit, is also a very reliable marker for assessing several concrete alterations.
Contact our Agronomy team for more information.