What are the deficiency symptoms of boron (B) in alfalfa?

The deficiency symptoms of boron in alfalfa primarily manifest as yellowing or reddening of only the upper leaves. This is because boron is crucial for various plant functions, including cell division and the development of new tissues. When there is a deficiency of boron, the young, actively growing tissues, particularly in the upper parts of the plant, exhibit visible symptoms first.

In the case of alfalfa, the upper leaves are more susceptible to stress factors, which can include nutrient deficiencies, and thus show alterations in color before the lower leaves exhibit any symptoms. The yellowing or reddening indicates a disruption in chlorophyll production and overall plant metabolism, a direct consequence of inadequate boron levels.

In contrast, other options describe symptoms associated with different nutrient deficiencies or conditions. For instance, stunting with purple undersides is typically linked to phosphorus deficiency, while interveinal chlorosis on lower leaves often relates to deficiencies in nutrients like magnesium or iron. The notion that deficiencies are seen only in wet years misrepresents how nutrient availability and plant uptake can fluctuate based on a wide range of environmental factors, not solely moisture levels. Understanding these specific symptoms and their links to boron deficiency is crucial for effective nutrient management in alfalfa cultivation