Holtschulze, Michael: Tipburn in head lettuce : the role of calcium and strategies for preventing the disorder. - Bonn, 2005. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5N-05794
@phdthesis{handle:20.500.11811/2194,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5N-05794,
author = {{Michael Holtschulze}},
title = {Tipburn in head lettuce : the role of calcium and strategies for preventing the disorder},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2005,
note = {In the present study the efficiency of preventive methods for the reduction of tipburn incidence was examined in head lettuce. Foliar applications of calcium chloride or short-term irrigation treatments were carried out in order to decrease tipburn incidence in the field. On the basis of root pressure measurements under controlled environment approaches should be made to explain the tipburn reducing effect of a reduction in VPD or the use of unsusceptible genotypes.
1. The efficiency of Ca-sprays depending on plant development and frequency of the application were examined in iceberg lettuce. Plants that were treated to the time of head formation showed a reduction in tipburn severity. An elevated foliar uptake due to the Ca-sprays could not be manifested by leaf mineral analysis.
2. Tipburn symptoms can be induced under controlled environmental conditions by a constant high VPD. Tipburn incidence could be reduced by a diurnal reduction of VPD. Contrary to the expectation this could not be explained by an encouraged root pressure flow during night time. Rather the concentration of mineral constituents in the root pressure exudate (K/Ca) seemed to be related to reduced tipburn incidence.
3. Shortly after the onset of short-term irrigation VPD within the crop stand was decreased. Tipburn incidence was influenced by the irrigation treatment depending on temperature and daily intervals. This diurnal reduction of VPD lead to a recurrent tendency of the efficiency of the short-term irrigation treatments throughout the planting sets. Although tipburn incidence could be reduced about 20 % by the irrigation treatments, however, the differences could not be calculated by statistical analysis.
4. Head lettuce genotypes expressed symptoms under controlled environmental conditions according to their variation in tipburn susceptibility. Higher growth rates during during early stages of plant development, lower specific leaf weight and also smaller cells per area could be observed in tipburn sensitive cultivars. Differences between the genotypes regarding tipburn incidence could not be explained by variations in the amount of root pressure flow. However, there was an effect on the qualitative compounds in the root pressure exudate, in particular during night time. This was most probably revealed by an increase of the K/Ca ratio during night period for the sensitive cv. ‘Herman’.},

url = {http://hdl.handle.net/20.500.11811/2194}
}

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