Quantitative analysis of prolonged reproductive growth of the tillers of Puccinellia chinampoensis population in alkalized meadow in the Songnen Plains of China Age structure of tillers of Hordeum brevisulatum clone in Songnen plain of China Analysis of the Reproductive-Tiller Quantitative Characters of Bothriochloa ischaemum Populations A Study on Photosynthetic Physiological Characters of Vegetative and Reproductive Tillers of Axonopus Compressus