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Cultivated bamboos are occasionally subjected to cold stress in winter, and silicon could improve their cold tolerance. However, evidence of the effect of Si on bamboos is still limited. Therefore, a batch and pot experiment was conducted for six months to investigate the effects of different Si fertilizer application rates (0, 0.5, 1.0, 2.0, 4.0, and 8.0 g kg−1 of soil weight) on the physiological responses and photosynthesis parameters of Phyllostachys praecox under a simulated cold stress condition. The cold temperature was set to 5 °C, 0 °C, and −5 °C, successively. The bamboo biomass increased significantly when the Si amendment rate was at least 2.0 g kg−1 (P = 0.002), and the highest biomass increase and root-to-canopy ratio were obtained with the 4.0 g kg−1 Si amendment. Furthermore, the Si contents in all organs of the bamboos increased with the increase of the Si amendment rate. The highest content of Si among the other organs was observed in the leaf, and the content was 68.95 mg kg−1 with the treatment of 4.0 g kg−1. With the application of Si, the photosynthesis rate of bamboo leaves was significantly increased (P = 0.008). The Si-amended bamboo exhibited a cold tolerance that was associated with stimulating antioxidant systems, and the enzyme activities of superoxide dismutase, peroxidase, and catalase increased with the increase of the Si amendment rate, whereas the malondialdehyde content and cell membrane permeability decreased with all Si treatments. A low temperature of −5 °C exerted effects on the bamboo leaf chloroplasts, but the ultrastructures of the chloroplasts remained intact after Si treatment. These findings suggest that Si fertilizer enhances bamboo growth and the tolerance of bamboo plants to cold stress. However, a high application rate (8.0 g kg−1) caused a decline in the bamboo biomass, compared to T4. Thus, a Si fertilization rate of 2.0~8.0 g kg−1 is recommended for bamboos under cold conditions.

Low-molecular-weight organic acids (LMWOAs) derived from root exudates and complexed with available metals in the rhizosphere soils of Taiwan red cypress (Chamaeyparis formosensis, FRS), peacock pine (Cryptomeria japonica, JRS), and moso bamboo (Phyllostachys pubescens, PRS) were identified by gas chromatograph (GC). The fresh plants (i.e., leaves, stems, roots, and litters) and soil samples of those three vegetations were examined for their organic functional groups. This study focused on (1) assessing methods for processing LMWOAs in the rhizosphere soils and fresh plants by GC analysis and (2) determining the relative proportions of organic carbon (C) functional groups in the three vegetations and fresh plant materials with 13 C nuclear magnetic resonance (NMR) analysis. The proportion of LMWOAs contents followed the order of PRS . FRS . JRS . bulk soils. The recovery and spiking tests analyzed by GC showed good recovery (.83.6%) and reproducibility of LMWOAs. The proportion of organic functional groups in the rhizosphere