ISHS Acta Horticulturae 367: VI International Symposium on Pear Growing
PHYSIOLOGICAL DISORDERS OF PEARS IN RELATION WITH NUTRITION |
| Authors: | G.F. Gil, J.A. Henríquez, C.A. Vera, J.P. Zoffoli |
| Keywords: | Pyrus communis, ammonium toxicity, calcium |
| Abstract:
Surveys have shown that fruit disorders, black end, black spots, black lenticels, occur in pear orchards of ‘Packham's Triumph’, ‘B. Bosc’, ‘B. D'Anjou’, and ‘Bartlett’ in Chile in coincidence with lower levels of calcium in the fruit around 15 days after full bloom (DAFB). Studies conducted in two orchards demonstrated that ‘Bartlett’ presented 23% of the fruits with some damage against 6% of ‘D'Anjou’ coinciding with lower calcium 15 DAFB and higher N/Ca ratio during most of the season. The effect of ammonium sulfate was studied in vitro using spurs with flower or fruit clusters. Continuous feeding with concentrations of 60 mM produced severe damage in most tissues. At 30 mM for 1 day only necrosis of stomata was observed but at 60 mM necrosis occured in leaves, sepals, and pedicels. At 15 mM a gradual necrosis developed starting with sepals and following with the distal end of the receptacle, producing “black end”. When clusters of 2 week old fruitlets were fed with 8 mM, fruitlets developed blackening of lenticels and black spots. The addition of ketoglutarate reduced but did not avoid the symptoms. Pear flowers and fruitlets appear as very sensitive to ammonium toxicity with low capacity for detoxification, and calcium may relieve the stress by competing with ammonium for absorption. | |
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