Interveinal chlorosis is a common plant issue that can affect various plant types, from houseplants to garden vegetables and landscape trees. This condition refers to a specific pattern of yellowing observed on plant leaves, which provides important clues about the plant’s overall health.
What “Interveinal” Means
The term “interveinal” describes the areas of a leaf located between its veins. A plant leaf includes a network of veins that act like the plant’s internal plumbing system, transporting water, nutrients, and sugars throughout the leaf.
The tissue that fills the spaces between these veins is known as the mesophyll. This mesophyll consists of two primary types of cells: the palisade mesophyll and the spongy mesophyll. The palisade layer, typically found directly beneath the upper surface of the leaf, contains elongated, tightly packed cells. Below this, the spongy mesophyll has irregularly shaped cells with large air spaces between them.
The Role of Interveinal Tissue
The interveinal areas are where most metabolic activity occurs. These cells are densely packed with chloroplasts, which contain chlorophyll, the green pigment capturing light energy. Photosynthesis, converting light energy, carbon dioxide, and water into glucose (sugar) and oxygen, occurs within these mesophyll cells.
Beyond sugar production, these interveinal tissues are also crucial for gas exchange. Tiny pores called stomata, often concentrated on the underside of leaves, open and close to regulate the flow of gases. Carbon dioxide enters through stomata and diffuses into the mesophyll for photosynthesis. Oxygen and water vapor are released from these areas. The sugars produced in the mesophyll cells are then transported out of the leaf to other parts of the plant for growth and energy.
Interveinal Symptoms in Plants
Interveinal chlorosis is a distinct symptom where the tissue between the leaf veins turns yellow, while the veins themselves remain green. This pattern is a direct result of a decline in chlorophyll production or activity within the mesophyll cells.
While interveinal chlorosis is the most common symptom observed in these areas, other issues can also appear. In severe cases, the yellowed interveinal tissue might progress to necrosis, the death of plant tissue, resulting in brown or dead spots. These visual cues serve as important indicators, often suggesting a problem with nutrient availability or transport to the metabolically active regions. Observing whether the symptoms appear on older or newer leaves can further narrow down the potential cause.
Identifying Causes of Interveinal Issues
Interveinal chlorosis is frequently a symptom of nutrient deficiencies. Several essential elements play a role in chlorophyll formation and overall plant health. For instance, iron deficiency is a common cause, leading to interveinal yellowing where the veins remain distinctly green, often appearing first on younger leaves because iron is immobile within the plant.
Magnesium deficiency also causes interveinal chlorosis, but it typically affects older leaves first, as magnesium is a mobile nutrient that the plant can relocate from older tissues to newer growth. Sometimes, red tints may develop between the veins alongside the yellowing. Manganese and zinc deficiencies can similarly present as interveinal chlorosis, with manganese issues often appearing on older leaves and sometimes causing dead patches.
While nutrient imbalances are primary culprits, other factors can contribute to these symptoms. An imbalanced soil pH can render nutrients unavailable to the plant even if they are present in the soil. Additionally, certain diseases, pest infestations, or even herbicide exposure can sometimes mimic interveinal patterns, though nutrient issues are more common underlying causes.