Stimulation of Photosynthetic Characteristics of Ginkgo Biloba L. during Leaf Growth

Photosynthetic pigments, biochemical activities and chlorophyll a fluorescence kinetics were investigated to survey the photosynthetic characteristics of Ginkgo biloba L. during leaf growth. The content of total chlorophyll increased rapidly while the content of carotenoids changed a little. The content of ATP, the activity of O2 evolution of chloroplasts, the electron transport activities, the activity of photophosphorylation and the activities of Ca and Mg ATPase were strengthened. All leaves at various growing stages exhibited typical chlorophyll a fluorescence transient, the intensity of fluorescence in the chlorophyll a fluorescence transient (OJIP) increased during leaf growth. Photosynthetic abilities gradually increased as the leaves grew. Introduction Leaf growth is a genetically controlled process (Sugiyama 2005). Morphological, anatomical and physiological traits significantly vary during leaf growth (Marchi et al. 2008). The development of the photosynthetic apparatus has been widely studied in both higher plants and algae. The formation of chloroplast ultrastructure, chlorophyll accumulation and the synthesis of the major components of the photosynthetic apparatus proceed almost in parallel and often result in a proportional increase of net photosynthesis (Šesták 1985). Ginkgo biloba L., also known as maidenhair tree, is a well-known living gymnosperm fossil with edible seeds, medicinal efficacy, and ornamental value, and is the only representative of the Ginkgoaceae family. Such unique characteristics of Ginkgo have attracted worldwide interest in plant science research. The genomics (Mohanta 2012) and the physiology (Skribanek et al. 2008) of Ginkgo have been thoroughly investigated. Earlier research showed that photo-protection was significantly strengthened at the early stages of leaf expansion in Ginkgo under natural environmental conditions and photosynthetic decline in Ginkgo leaves during natural senescence (Yang et al. 2012, 2013). However, there have been no studies focusing on the analysis of leaf photosynthetic and physiological traits of Ginkgo during leaf growth. The changes in photosynthetic pigments, biochemical activities and chlorophyll a fluorescence kinetics were investigated to survey the photosynthetic characteristics of Ginkgo during leaf growth. Materials and Methods Ten-year-old male Ginkgo biloba cv. ‘Dafozhi’ plants were grown in field situated in Jiangdu, Jiangsu Province, P.R. China (32°26′N, 119°38′E). Leaf samples were collected at 08:00 a.m., immediately frozen in liquid nitrogen, and stored at –80oC until analysis. The fresh leaves were washed with distilled water and the petioles removed. The samples were extracted in ice-cold 80% acetone, and the extract was centrifuged at 6000 × g for 10 min. After collecting the top solution, the precipitate was supplemented with icecold 80% acetone, and centrifuged again for another 10 min. The supernatant was measured with *Author for correspondence. . College of Life Science, Nanjing Normal University, Nanjing 210023, P.R. China. .