Abstract: This paper studied the seasonal variation of iron content in different organs of Calamagrostis angustifolia, Carex meyeriana, and C. lasiocarpa, the dominant plant species on the natural wetland of Sanjiang Plain, and of soybean (Giycine max) and rice (Oryza sativa), the main crops planted on the wetland farmland of the Plain. In late growth season (September), the iron content in C. angustifolia, C. meyeriana, and C. lasiocarpa all presented a pyramid form, with the leaf iron content at the top of pyramid being 308%, 442%, and 118% of the sod layer (20〖KG-*2〗-〖KG-*7〗30 cm) iron content at the bottom of pyramid, respectively; while in early growth season (May), the profile of iron content fitted Logistic model well (R2=1000, 09902, and 09954, respectively). In the whole growth season, the iron content in the underground part of test wetland plants decreased gradually, while that in aboveground part changed with species and organs. By contrast with that of wetland plants, the iron pool of wetland farmland crops was mainly in roots, and increased with time during the growth season. The iron content in the aboveground part of the crops was far lower than that in crop roots, and in the aboveground part, leaf had the highest iron content. During growth season, the mean increasing rate of leaf iron content was higher for rice (7561%) than for soybean (567%). At maturing stage, the iron content in the grains of soybean and rice was the lowest, only being 550% and 044% of that in roots. The iron content in the same organs of different plant species varied with growth stage, and the iron accumulation of wetland plants was more significant than that of wetland farmland crops.

Key words: Shadow width, Relative light illuminance, Leaf area density function, Light wakening coefficient