Photosynthesis and respiration in the needles of Pinus sibirica and Pinus pumila and their putative hybrids

Abstract

A putative interspecific hybridization in Pinaceae family was investigated. Very rarely the physiological methods were involved in hybridization processes that occurs in the hybrid zones. It is well known that in most gymnosperms, the plastid genome is inherited from the paternal component while the mitochondrion is inherited from the maternal one. Therefore functioning pattern of organelles in the hybrid plant can suggest parent, from which they were inherited. The aim of this study was to indirectly establish the inheritance energy-transducing organelles (mitochondria, chloroplast) according to their functioning. Current year needles from Siberian Stone Pine (Pinus sibirica Du Tour) and Japanese Stone Pine (Pinus pumila (Pall.) Regel) as parent species and their putative hybrids were collected from Baikal Region. The photosynthesis rate was determined by using the spectrophotometer. The study of emission CO2 under dark respiration of needle was conducted with laser optical-acoustic gasanalyzer. The quantity was measured at 1, 2 and 3 hour after experiment start. The rate of the photoreduction ferricyanide potassium was characterized by the primary photochemical processes activity at the level of photosystem II. Comparison of pure species was shown that Japanese Stone Pine had higher functional activity of chloroplast as compared with Siberian Stone Pine in spite of the fact that they are growing in similar environment conditions. Two of three analyzed hybrids had decreased activity of their chloroplasts. Unfortunately, in this case we can't conclude if the chloroplasts were inherited from Siberian Stone Pine or from Japanese Stone Pine. Chloroplast activity of the third hybrid was approximately similar to that of Japanese Stone Pine suggesting that its chloroplasts were inherited from this parent. Consequently, the Siberian Stone Pine and the Japanese Stone Pine were maternal and paternal, respectively parents of the hybrid. Compared to the Siberian Stone Pine, the Japanese Stone Pine had higher dark respiration rate. The hybrid respiration rate was similar to that of the Japanese Stone Pine suggesting that the hybrid inherited mitochondria from this species. Our findings indicated that the P. pumila exhibited particular ecological plasticity and this phenomenon is attributable to its high potential activity of photosynthetic and respiratory processes. These physiological features explained the large transcontinental natural habitat of Japanese Stone Pine.