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A tissue analysis trial for the diagnosis of nitrogen level was performed during the 2001 growing season in Paine County, Metropolitan Region, Chile. Seven-year-old 'Hass' avocado (Persea americana Mill.) trees were soil treated with urea at rates of 0, 333, 666, and 999 g N/tree, split in two applications (2 and 4 months after fruit set). Each treatment was applied to three randomly selected trees. Fifty spring fl ush leaves and fi f- teen fruit peduncles were taken per tree 4 months after application. Two months later, 70 panicles per tree were taken, and nitrogen concentration in these samples was determined by Kjeldahl digestion. Differences between treatments were better detected in peduncle and infl orescence samples than in leaf samples. The relationship between nitrogen dose and nitrogen concentration in the tissue was R 2 = 0.67, 0.65, and 0.56 in peduncle, leaf, and infl orescence, respectively. Consequently, peduncle appears a promising tissue, probably better than leaf, for diagnosing the nitrogen status of avocado trees. Tissues other than the leaf have been mentioned for the nutritional diagnosis of fruit plants. Fregoni (1980) stated that fl owers are very useful to study some nutrient defi cien- cies, mainly boron, in grapevine. A similar statement has been made by Nyomara and Brown (1997) for fruit hull in almond, being the tissue with higher accumulation of boron. According to Montanes et al. (1997) and Sanz et al. (1997), fl ower analysis could be a use- ful indicator of the nutritional status, mainly of iron, in peach and other fruit trees. Dulac, cited by Fregoni (1980) found that the cluster stalk represents the response of potassium ap- plication to the soil in grapevine better than the leaf. Similarly, Ismail, cited by Fregoni (1980), reports a linear response in nitrogen content of grapevine cluster stalk to increasing doses of nitrogen to the soil. In a nutritional survey carried out in 14 'Hass' avocado groves growing under different conditions of soil at the Central Zone of Chile, where leaf, infl orescence, fruit peduncle, fruit fl esh and seed were analyzed, Granger (2001) found that the infl orescence (panicle) had the highest nitrogen content. She also found that nitrogen concentration in the fruit peduncle showed the greatest variation among groves (Table 1). These results suggested the use of both tissues as promising tools to determine the level of nitrogen supply in this species. Consequently, the objective of the present trial was to determine the relationship between soil nitrogen fertilization and nitrogen con- centration in the leaf, the infl orescence and the fruit peduncle to compare the effi cacy of these tissues as nutritional diagnostic tools in avocado trees.

The Inflorescence and Fruit Peduncle as Indicators of Nitrogen Status of the Avocado Tree