Nitrogen status influence on olive tree flower quality and ovule longevity

In the course of a long-term experiment we investigated the influence of olive tree nitrogen status on flower development and quality in two different years. Three N status levels were compared, based on leaf nitrogen status in July: low (0.98-1.32%), adequate (1.43-1.57%) or high (1.69-1.93%) leaf nitrogen concentration of July samples. With few exceptions, the inflorescence parameters generally showed no significant differences among years or treatments. For 2002, values were significantly higher for the adequate N level as compared to high N for number of nodes, for high N as compared to low N for percent perfect flowers, and high and adequate N as compared to low N for percent fertile inflorescences. However decreased water availability during the pre-flowering period also could have reduced the number and percent of perfect flowers during that year. For perfect flowers, N level had no affect on either ovule differentiation or ovary, mesocarp and endocarp size. Ovule viability decreased, though, both in the low N trees, as has been shown previously in other tree fruits, and also in the high N trees, as compared to those with adequate N level. These results suggest that nitrogen excess could reduce ovule longevity to the same extent as nitrogen deficiency, and indicate the importance of maintaining an adequate nitrogen status for potential fertilization and fruit set. (c) 2008 Elsevier B.V. All rights reserved.