Nitrogen Stress in Birch Seedlings
Tóm tắt
An account is given of experiments with birch (
During a lag phase the seedlings in the sub optimum treatments had rapidly diminishing growth rates, deficiency symptoms, and a relatively high root growth rate with formation of long, thin roots. When the growth rate later on had stabilized, a period was recognized during which measurements and sampling were carried out. At the end of the lag phase, or in the beginning of the experimental period, the nitrogen deficiency symptoms of the leaves disappeared and the various parts of the seedlings grew with the same rate, and in a good linear correlation with the rate of nitrogen supply.
The results indicate that nitrogen primarily influences the leaf area growth rate, which responds rapidly to a change in nitrogen availability. The following general growth response demonstrates the ability of the plants to adapt growth according to nitrogen supply, so as to create stable internal physiological conditions. Thus, there is a close agreement between the rate of nitrogen supply and consumption on one hand and growth rate on the other.
The characteristic nitrogen deficiency symptoms of the seedlings during the lag phase are very similar to those reported in the literature. During the stable period that follows, they disappear from the leaves in agreement with the fact that natural vegetation generally is green also when nitrogen is strongly growth limiting. It is concluded that the exponentially increasing amounts of nitrogen added to lie nutrient solution, also when the exponent is far below optimum, makes nitrogen available to the seedlings in a similar way as does the exponentially growing root system in. a solid medium. Birch seedlings are able to adapt growth rate to low nitrogen supply and thereby show a healthy appearance without acute deficiency symptoms. Some ecological and practical implications are discussed.
Từ khóa
Tài liệu tham khảo
Aronsson A., 1977, Elimination of water and mineral nutrition as limiting factors in a young Scots pine stand. I. Experimental design and some preliminary results, Swedish Coniferous Forest Project. Technical Report, 10, 1
Dahl I., 1973, Intercalibration of methods for chemical analysis of water. IV. Results from intercalibrations of the indo phenol blue method for determination of ammonia, Vatten, 29, 336
Dahl I., 1974, Intercalibration of methods for chemical analysis of water. V. Results from intercalibration methods for determining nitrate and total nitrogen, Ibid, 30, 180
Ingestad T., 1962, Macro element nutrition of pine, spruce, and birch seedlings in nutrient solutions, Medd. Statens Skogsforskningsinst., 51, 1
Ingestad T.1968.Versuche mit konstantem inneren Ernährungszustand in Birkenpflanzen.Tagungsberichte NT 84. Tharandt DDR1965:71–76.
Ingestad T., 1971, Recent Advances in Plant Nutrition, 633
Ingestad T., 1973, Mineral nutrient requirements of Vaccinium vitis idaea and V. myrtillus, Ibid, 29, 239
Ingestad T., 1974, Towards optimum fertilization, Ambio, 3, 49
Ingestad T., 1977, Nitrogen and plant growth; Maximum efficiency of nitrogen fertilizers, Ambio, 6, 146