Photosynthesis, being the basis of production process, comes under the influence of ecological factors, adapting to their various combinations and intensity. During the vegetative period of 1976-1986 in 80 km to the northeast of Irkutsk in the for-est-steppe of the Baikal territory visible photosyn-thesis of needles of Scotch pine by a gas measur-ing method with the use of assimilatory chambers was investigated. In parallel with the standard methods environment factors were registered: solar radiation, temperature and humidity of the air and the soil. Day changes of visible photosynthesis of biannual needles were classified according to three types of curves. The first type was noted in mois-tening conditions, optimum or close to optimum, on sunny days, the second with several peaks was observed on cloudy days, the third type was regis-tered when the reserves of available soil moisture in the top of 50 centimeter, most root zone layer of soil was significantly exhausted. The intensity of visible absorption of CO2 in biannual needles of the pine was registered within 40-50 days of each vegetative period used for the determination of de-pendence of photosynthesis on environment fac-tors. Light curve of photosynthesis of needles at an optimum of soil moistening had a little stretched excess area, rather big tilt angle of an initial piece. The temperature of maximum of photosynthesis with the increase in the deficiency of soil moisten-ing was noted in the field of lower air temperatures (12-14 оС) in comparison with its size (20-22 оС) at optimum moistening. The types of day course and ecological dependencies of photosynthesis were presented by regression equations, using the poly-nomial function of the sixth order characterized by the approximation coefficient changing within 0.64-1.0. It was as much as possible approximated by polynomial function and dependence of day effi-ciency of photosynthesis of needles on a reserve of available soil moisture, i.e. ecological factor having direct impact on efficiency of photosynthesis of a pine ordinary in the forest-steppe of the Baikal terri-tory.
Scotch pine, air temperature and humidity, rainfall, humidity of the soil, visible photo-synthesis, factorial dependencies
1. Zabuga V.F., Zabuga G.A. Dyhanie sosny obyknovennoy. - Novosibirsk: Nauka, 2013. - 208 s.
2. Molchanov A.G. Balans SO2 v ekosistemah sosnyakov i dubrav v raznyh lesorasti-tel'nyh zonah. - Tula: Grif i K, 2007. - 284 s.
3. Atlas Irkutskoy oblasti. - M.; Irkutsk, 2004. - 90 s.
4. Elagin I.N. Sezonnoe razvitie sosnovyh lesov. - Novosibirsk: Nauka, 1976. - 230 s.
5. Voznesenskiy V.L. Fotosintez pustynnyh rasteniy (Yugo-Vostochnye Karakumy). - L.: Nauka, Leningr. otd-nie, 1977. - 256 s.
6. Lang Y., Wang M., Zhang G.C. [et al.]. Exper-imental and simulated light responses of pho-tosynthesis in leaves of three tree species un-der different soil water conditions // Photosynthetica. - 2013. - V.51. - P. 370-378.
7. Peters J., Morales D., Jiménez M.S. Gas ex-change characteristics of Pinus canariensis needles in a forest stand on Tenerife, Canary Islands // Trees. - 2003. - V. 17. - P. 492-500.
8. Peters J., González-Rodriguez A.M., Jiménez M.S. [et al.]. Influence of canopy position, needle age and season on the foliar gas ex-change of Pinus canariensis // European Jour-nal of Forest Research. - 2008. - V.127. - P. 293-299.
9. Yang Y., Li C. Photosynthesis and growth ad-aptation of Pterocarya stenoptera and Pinus elliottii seedlings to submergence and drought // Photosynthetica. - 2016. - V. 54. - P. 120-129.
10. Yuzbekov A.K., Zamolodchikov D.G., Ivashchenko A.I. Spruce fir photosynthesis in the forest ecosystems of the Log Tayezhnyi test area // Moscow University Biological Sci-ences Bulletin. - 2014. - V.69. - P.169-172.
11. Zagirova S.V. Structure, pigment content, and photosynthesis of Siberian larch needles in Northern and Sub-Arctic Urals // Contempo-rary Problems of Ecology. - 2015. - V. 8. - P. 871-878.
12. Zhu J., Wang K., Sun Y. [et al.]. Response of Pinus koraiensis seedling growth to different light conditions based on the assessment of photosynthesis in current and one-year-old needles // Journal of Forestry Research. - 2014. - V. 25. - P. 53-62.
