Growth habit and photosynthetic activity of shoot cultures of Medicago sativa L. transformed with the oryzacystatin II gene

Abstract

Background and Purpose: Introduction of a foreign gene into plant genome may induce morphological and physiological alterations in transgenic plants. The purpose of this study was to assess the impact of gene introduction on morphology and photosynthetic activity of two transgenic alfalfa shoot cultures. Material and Methods: In vitro maintained shoot cultures of alfalfa (Medicago sativa L. cv. Zajecarska 83) that were transformed with the oryzacystatin II (OC-II) gene and propagated on growth regulator-free medium were subjected to analysis of morphological characteristics and photosynthetic activity. For analysis of morphological characteristics, the length of the main axis, the number of axillary and adventitious shoots, total number of leaves and the number of senesced leaves as well as plant dry mass were determined. Net photosynthetic rate was determined as CO(2) influx using a LI-6200 closed photosynthesis system. Photosynthetic function was assessed as the rate of basic chlorophyll fluorescence and determined with a Plant Stress Meter by method of induced fluorometry. Chlorophyll content in leaf samples was determined spectrophotometrically. Results: The most striking feature of transformed cultures was reduced apical dominance and the absence of adventitious roots. In comparison with Control, main axis length was also reduced. In addition, a general den-ease in photosynthesis in transgenic shoots was also observed. Conclusion: Both morphology and the key processes in photosynthesis were modified in transgenic shoots. However, the fact that transgenic plants carry a gene that confers pest resistance gives potential agronomic value to at least some of the clones whose morphological characteristics and photosynthetic activity were minimally, disturbed.