Coffee leaf and stem anatomy under boron deficiency

Abstract

SUMMARYBoron 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. Bdeficient leaves had fewer and deformed stomata.

Absorption and mobility of foliar-applied boron in soybean as affected by plant boron status and application as a polyol complex

“…2). Several studies showed that B deficiency induced leaf structural changes including abnormal stomatal morphology and altered functionality (Oosterhuis and Zhao 2001;Rosolem and Leite 2007;Sharma and Sharma 1987;Sheng et al 2009) but the underlying mechanisms of this physiological response to B deficiency remain speculative.…”

“…Physiological responses of plants to B deficiency include the loss of membrane integrity and cell wall stability, which result in the development of structural damage in crop plants like for instance, cracked stem in celery, stalk rot in cauliflower, heart rot and internal black spot in beet, top rot in tobacco and internal cork in apple (Blevins and Lukaszewski 1998). Several studies showed that B deficiency induces leaf structural changes, including abnormal stomata and distorted guard cells in cauliflower (Sharma and Sharma 1987) and coffee (Rosolem and Leite 2007) or decreased stomatal conductance and transpiration rates in navel orange and cotton (Oosterhuis and Zhao 2001;Sheng et al 2009). Many other effects associated with B imbalances have been described, but the direct role of B in metabolism is still little understood.…”

Carbohydrate production and transport in cotton cultivars grown under boron deficiency

“…The response in the 4 th week after B1 was similar to the response after the 1 st week, although the values were lower ( Figure 2B). In the absence of B, plant morphological changes occur, especially in the leaves (Oliveira et al, 2006), with a decrease in the number and functioning of stomata (Rosolem and Leite, 2007), which might impair transpiration ( Figure 2B) and CO 2 fl ow in intercellular spaces ( Figure 2A). Stomatal conductance was higher at B1 than at one and four weeks later, although the responses were similar in the three assessments.…”

“…At 20 µmol L −1 B, the values tended to decrease, possibly due to a toxic effect of B ( Figure 2C). The lower stomatal conductance of plants in the absence of B might have resulted from morphological changes in leaves and detrimental changes in stomata (Rosolem and Leite, 2007). Decreased carbohydrate transport, which is observed under B defi ciency, causes the accumulation of starch in leaves (Zhao and Oosterhuis, 2002), which might impair physiological activity by increasing the physical restriction inside leaves, resulting in poor stomatal function.…”

Mineral nutrient calibration for Cassava (Manihot esculenta Crantz) grown in dry-tropical North-Eastern Queensland, Australia: with a focus on Phosphorus and Boron

“…Other symptoms of B deficiency include disorganization of vascular tissue, discontinuities in xylem structure, thinner xylem walls, fewer stomata and increased stomata deformity in soybean (Glycine max (L.) Meer. ), coffee (Coffea arabica) and cotton plants (Gossypium hirsutum) (Oosterhuis and Zhao, 2001;Rosolem and Leite, 2007;Will et al, 2011).…”