measurement methods of soil, water, plant and fruit, in berry ... - NJF
measurement methods of soil, water, plant and fruit, in berry ... - NJF
measurement methods of soil, water, plant and fruit, in berry ... - NJF
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A METHODOLOGY FOR STUDIES OF DORMANCY AND<br />
WATER CONTENT OF FLORAL BUDS IN SOUR CHERRY<br />
CV. STEVNSBÆR<br />
Ivar Dencker, KVL, Agrovej 10, 2630 Taastrup, Danmark<br />
Torben Toldam Andersen, KVL, Agrovej 10, 2630 Taastrup, Danmark<br />
The sour cherry ’Stevnsbær’ suffers severely from bud damages dur<strong>in</strong>g w<strong>in</strong>ter <strong>in</strong> both<br />
Denmark <strong>and</strong> Sweden. The floral mortality may exceed 90 percent on annual shoots. It is now<br />
known that this bud damage can occur already <strong>in</strong> December, be<strong>in</strong>g caused by night frosts <strong>of</strong><br />
only –6 to –9 0 C <strong>in</strong> both year 1999 <strong>and</strong> 2000. It is also known that there is a strong negative<br />
relationship between the <strong>water</strong> content <strong>of</strong> the flower bud <strong>and</strong> the actual frost hard<strong>in</strong>ess. This<br />
experiment was carried out to study the <strong>water</strong> content <strong>and</strong> dormancy <strong>of</strong> flower buds <strong>in</strong><br />
‘Stevnsbær’ dur<strong>in</strong>g autumn <strong>and</strong> early w<strong>in</strong>ter year 2000-2001. In the period August-January,<br />
lateral flower buds were sampled from the base <strong>and</strong> tip <strong>of</strong> annual shoots <strong>of</strong> trees from<br />
different irrigation <strong>and</strong> fertilizer treatments. The buds were put <strong>in</strong>to sealed plastic tubes,<br />
placed on ice <strong>and</strong> immediately brought to the lab for fresh <strong>and</strong> dry matter determ<strong>in</strong>ations.<br />
Furthermore, <strong>in</strong> September-January shoot pieces from the same dates <strong>and</strong> trees as above were<br />
forced for six days at +20 0 C <strong>in</strong> a climate chamber, whereafter the buds were broken <strong>of</strong>f <strong>and</strong><br />
weighed as <strong>in</strong> the field sampl<strong>in</strong>gs. Dur<strong>in</strong>g autumn a major decrease <strong>in</strong> the <strong>water</strong> content <strong>of</strong><br />
flower buds was recorded <strong>in</strong> all treatments. Lateral buds near the shoot tip had a markedly<br />
higher <strong>water</strong> content than buds at the shoot base, <strong>and</strong> this difference persisted throughout the<br />
sampl<strong>in</strong>g period. The forc<strong>in</strong>g <strong>of</strong> buds under optimized grow<strong>in</strong>g conditions showed that buds<br />
rema<strong>in</strong>ed dormant only until the middle <strong>of</strong> November. From late November <strong>and</strong> throughout<br />
the rest <strong>of</strong> the sampl<strong>in</strong>g period forced buds turned green <strong>and</strong> swelled dist<strong>in</strong>ctly, <strong>and</strong><br />
simultaneously such forced buds had a sharp <strong>in</strong>crease <strong>in</strong> <strong>water</strong> content. Bud dormancy was<br />
gone <strong>in</strong> late November <strong>in</strong> all treatments. The lack <strong>of</strong> bud dormancy <strong>in</strong> December may expla<strong>in</strong><br />
the comprehensive bud damages occurr<strong>in</strong>g <strong>in</strong> Stevnsbær: A warm period <strong>in</strong> the beg<strong>in</strong>n<strong>in</strong>g <strong>of</strong><br />
December (as <strong>in</strong> year 2000) may force the buds, <strong>in</strong>creas<strong>in</strong>g their <strong>water</strong> content <strong>and</strong><br />
subsequently a sudden but not very severe freeze (as <strong>in</strong> year 2000) would cause frost<br />
damages. The usability <strong>of</strong> <strong>water</strong> content <strong>measurement</strong>s <strong>in</strong> floral buds to predict frost hard<strong>in</strong>ess<br />
is discussed.<br />
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