Early effects of long nights on budset, bud dormancy and abscisic acid content in two populations of Picea abies
1995
Qamaruddin, M. | Ekberg, I. | Dormling, I. | Clapham, D. | Eriksson, G. (Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Forest Genetics) | Norell, L.
The daily variation of free and conjugated abscisic acid (ABA) following long night treatments and the number of long nights needed to initiate budset and the build-up of bud dormancy were investigated in seedlings of a northern (north Sweden, estimated critical night length of 2 h) and a southern (Romanian, estimated critical night length of 7.5 h) population of Picea abies cultivated in a phytotron. After continuous growth the seedlings from both populations were exposed to a regime of 16 h nights for one up to 9 days. In a second experiment the northern seedlings were given 5 h nights for one up to 12 days. Only one night with 16 h was needed to induce almost 100 budset about 14 days later in the northern population whereas 4 nights were needed for the southern population. When the northern population was given 5 h nights, the number of nights required for 100 % budset increased to 5. Dormancy built up more rapidly in the northern than in the southern population. The northern population reached the same degree of dormancy after 3 nights of 16 h as the southern population after 8 nights of 16 h. The northern population built up dormancy more slowly but to a higher final level when exposed to 5 h nights than when exposed to 16 h nights. A transient peak in the content of free ABA in the needles of the northern population was observed at day 4 with 16 h nights. The peak was not attributable to changes in water status of the shoots. The peak in the levels of free ABA in the needles of the southern population occurred after 8 days with 16 h nights. Following exposure to 5 h nights - a less abrupt change- the peak of ABA was smoothed out for the northern populations
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