Photosynthetic Characteristics of Wild Plant Species with Extremely Small Populations <i>Cycas Shiwandashanica</i>

Abstract

Cycas Shiwandashanica  is classified as an extremely small populations of cycads due to its fragmented habitat and scarce wild resources. The growth indexes of annual and biennial seedlings from Cycas Shiwandashanica  were determined, and diurnal photosynthetic changes and photosynthetic response curves of biennial seedlings were measured by Li-6400 portable photosynthetic apparatus. The results showed that the seedling height, ground diameter and crown width of the biennial seedlings were significantly higher than those of the annual seedlings, it can be grown well in this habitation. The daily change of net photosynthetic rate P n  of Cycas Shiwandashanica  was bimodal curve, with the two peaks appearing at 10:30 am and 14:30 pm, and the net photosynthetic rates were 1.73 μmol·m -2 ·s -1  and 1.76 μmol·m -2 ·s -1 , respectively, and the net photosynthetic rate was limited by stomatal factors and non-stomatal factors. It belongs to the mesophytic plant, with a light compensation point (LCP) of 3.68 μmol·m -2 ·s -1 , a light saturation point (LSP) of 1023.67 μmol·m -2 ·s -1  and a maximum photosynthetic rate ( P max ) of 3.57 μmol·m -2 ·s -1 . This study by measuring the growth potential and photosynthetic characteristics, reveals the photosynthetic characteristics of the Cycas Shiwandashanica  for the first time. It provides technical support for the protection, introduction and cultivation of Cycas Shiwandashanica , provides theoretical support for the mitigation of the endangered status of Cycas Shiwandashanica , and has theoretical value and guiding significance for the protection research of it.