Acao do vento e da radiacao solar na ruptura do pulvino foliar do cacaueiro
Experiments in which cacao (Theobroma cacao L.) seedlings were submitted to various combinations of field and wind tunnel treatments, involving protection and exposure to solar radiation and wind, have shown a synergistic interaction of these two factors upon the mechanical injury caused by the wind at the pulvinus level. Visible damage to the pulvinii occurred shortly after the plants were exposed to wind. Injury progressed rapidly, leading to intensive leaf fall and severe damage to the epidermic and cortical tissues of the pulvinus. The vascular bundles in this region were ultimately ruptured by continuous exposure, as shown by anatomic studies. Wind sheltering on its own (no overhead shade) avoided mechanical injury almost as effectively as both wind and overhead shade protection. Thus, at radiation levels higher than 250 cal.cm-2 day-1 the extent of the damage ranged from 0 - 22.9 per cent in the former and from only 0 - 2.6 per cent in the latter treatment. In plants not surrounded by wind breaks, on the other hand, wind speeds higher than 2.5 m.s.-1 ruptured 60 - 100/per cent of the pulvinii in the absence of overhead shade, whereas shaded plants were less damaged (20 - 60 per cent). It is concluded that it is more effective to provide to cacao seedlings protection against excessive wind rather than against solar radiation, as far as mechanical injury is concerned
| Main Authors: | , , |
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| Format: | biblioteca |
| Published: |
1980
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| Subjects: | THEOBROMA CACAO, HOJAS, DAÑOS POR EL VIENTO, DAÑOS POR RADIACION, DAÑOS MECANICOS, PULVINULO, |
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| Summary: | Experiments in which cacao (Theobroma cacao L.) seedlings were submitted to various combinations of field and wind tunnel treatments, involving protection and exposure to solar radiation and wind, have shown a synergistic interaction of these two factors upon the mechanical injury caused by the wind at the pulvinus level. Visible damage to the pulvinii occurred shortly after the plants were exposed to wind. Injury progressed rapidly, leading to intensive leaf fall and severe damage to the epidermic and cortical tissues of the pulvinus. The vascular bundles in this region were ultimately ruptured by continuous exposure, as shown by anatomic studies. Wind sheltering on its own (no overhead shade) avoided mechanical injury almost as effectively as both wind and overhead shade protection. Thus, at radiation levels higher than 250 cal.cm-2 day-1 the extent of the damage ranged from 0 - 22.9 per cent in the former and from only 0 - 2.6 per cent in the latter treatment. In plants not surrounded by wind breaks, on the other hand, wind speeds higher than 2.5 m.s.-1 ruptured 60 - 100/per cent of the pulvinii in the absence of overhead shade, whereas shaded plants were less damaged (20 - 60 per cent). It is concluded that it is more effective to provide to cacao seedlings protection against excessive wind rather than against solar radiation, as far as mechanical injury is concerned |
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