Coffee leaf and stem anatomy under boron deficiency

Ciro Antonio Rosolem,Vagner Maximino Leite

doi:10.1590/s0100-06832007000300007

Ciro Antonio Rosolem, Vagner Maximino Leite

Open Access

https://doi.org/10.1590/s0100-06832007000300007

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Abstract

Boron deficiency in coffee is widely spread in Brazilian plantations, but responses to B fertilizer have been erratic, depending on the year, form and time of application and B source. A better understanding of the effects of B on plant physiology and anatomy is important to establish a rational fertilization program since B translocation within the plant may be affected by plant anatomy. In this experiment, coffee plantlets of two varieties were grown in nutrient solutions with B levels of 0.0 (deficient), 5.0 µM (adequate) and 25.0 µM (high). At the first symptoms of deficiency, leaves were evaluated, the cell walls separated and assessed for B and Ca concentrations. Scanning electron micrographs were taken of cuts of young leaves and branch tips. The response of both coffee varieties to B was similar and toxicity symptoms were not observed. Boron concentrations in the cell walls increased with B solution while Ca concentrations were unaffected. The Ca/B ratio decreased with the increase of B in the nutrient solution. In deficiency of B, vascular tissues were disorganized and xylem walls thinner. B-deficient leaves had fewer and deformed stomata.

Highlights

Coffee is one of the most B-sensitive and responsive species (Brown & Shelp, 1997)
Boron deficiency is widespread in Brazilian plantations (Malavolta, 1986; Malavolta et al, 2001), resulting in a reduced root system, flower abortion, fruit malformation and low yields (Franco, 1982)
Boron fertilizer is recommended in Brazil when soil B is below 0.06 mg dm-3 (Raij, 1996) or leaf B content below 60 mg kg-1 (Malavolta et al, 2001), but responses of coffee trees to B fertilizer have been erratic, depending on the year, way and time of application and B source (Santinato et al, 1991; Almeida & Matiello, 1996)

Summary

SUMMARY

Boron deficiency in coffee is widely spread in Brazilian plantations, but responses to B fertilizer have been erratic, depending on the year, form and time of application and B source. A better understanding of the effects of B on plant physiology and anatomy is important to establish a rational fertilization program since B translocation within the plant may be affected by plant anatomy. In this experiment, coffee plantlets of two varieties were grown in nutrient solutions with B levels of 0.0 (deficient), 5.0 μM (adequate) and 25.0 μM (high). Scanning electron micrographs were taken of cuts of young leaves and branch tips The response of both coffee varieties to B was similar and toxicity symptoms were not observed. Com deficiência de B, os tecidos vasculares foram desorganizados e as paredes do xilema ficaram mais finas. Termos de indexação: deficiência de boro, relação Ca/B, nutrição do cafeeiro, estômatos

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