What is new in boron nutrition? Case study on African mahogany leaf anatomy

ABSTRACT

Fertilization with boron (B) is a crucial aspect in the management of tropical soils to achieve high yield and wood quality in forest species. However, studies are still needed for a better understanding of the effects of B on the anatomy and physiology of African mahogany to improve borate fertilization programs in terms of doses and sources of B. The objective was to characterize the morphology and anatomy of African mahogany leaves subjected to doses and sources of B, as well as to investigate leaf lesions caused by excess B. In a 3 × 3 factorial scheme, a randomized block design was used with four replications, resulting in a total of 36 experimental units. The treatments consisted of three sources of B: borax (sodium tetraborate), ulexite, and colemanite, and three doses of B: 0, 1.5, and 3 mg dm ^–3 . After 120 days of transplanting, leaf samples with and without toxicity lesions were collected for morphological and anatomical evaluations. Following the collection, the samples were photographed and fixed in Karnovsky’s solution. The plants cultivated in the control treatment did not exhibit any symptoms of B deficiency in the leaf tissue. Borax and ulexite sources, and higher doses of B resulted in greater lesions, accompanied by the accumulation of phenols in the necrotic region. In contrast, the source of lower solubility (colemanite) and lower dose of B demonstrated the highest accumulation of starch. African mahogany is sensitive to applying high doses (3 mg dm ^–3 ) and high solubility sources of Boron (borax). Excessive B levels cause necrosis and structural disorganization of African mahogany leaf tissues.

histopathology; micronutrient; morphology