Frost hardiness development in Pinus silvestris seedlings in response to fertilization [temperature resistance, chlorophyll, conifers, nitrogen]
1981
Hellergren, J. (Lund Univ. (Sweden). Dept. of Plant Physiology)
The effects of different levels of nitrogen on freezing survival, the amounts of chlorophylls and Beta-carotene, the ratios Chl a/Chl b, and (Chl a + Chl b)/Beta-carotene in hardened and unhardened seedlings of Scots Pine (Pinus silvestris L.) have been investigated. There was no correlation between frost hardiness and nitrogen content in the unhardened seedlings. However, the hardy seedlings with the highest nitrogen content, showed a decrease in frost hardiness of 3 deg C. The amounts of chlorophylls and Beta-carotene increased for all the treatments during hardening, except for the seedlings that had the highest nitrogen content: so that the effect of fertilizer was more evident in non-hardened than in hardened plants. The ratios Chl a/Chl b decreased during hardening in all the treatments. This was an effect of a larger increase of Chl b than Chl a. The ratios of Chl a + Chl b/Beta-carotene also decreased during hardening except for the plants that were fertilized with the second lowest amount of nitrogen. Since the amounts of Chl a and Chl b increase during hardening the amount of Beta-carotene increases even more. The growth rates of the seedlings were closely related to the nitrogen content for the different treatments. All plants were infected with ectotrophic mycorrhizae, which resulted in an enhancement of ion transportation from the soil to the plants. This is important when the supply of ions is low.
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