Effects of Rocky Desertification Stress on Oat (Avena sativa L.) Seed Germination and Seedling Growth in the Karst Areas of Southwest China

Oat is an important crop widely distributed in temperate zones and is also commonly planted in the karst areas of southwest China. However, due to severe rocky desertification, the complex soil in this area is characterized by high calcium content, alkaline conditions, and drought, which significantly negatively impact the growth of oat seedlings. To study the adaptability of oats to rocky desertification stress at the seedling stage, we investigated the effects of CaCl₂ (0-150 mM), the pH (3-9), and drought stress (PEG-6000 solution at 0 to -0.79 MPa) on seed germination and seedling growth. The results showed that (1) calcium stress had dual effects on seed germination within the range of 5-150 mM CaCl₂. Low concentrations of CaCl₂ (5 mM) promoted the germination potential, germination rate, germination index, and vigor index of oats, as well as the growth and biomass accumulation of radicles in oat seedlings; however, high concentrations of CaCl₂ inhibited these germination parameters. (2) Under drought stress, moderate concentrations of a PEG-6000 solution significantly improved the germination potential and germination rate of oat seeds, but the germination index and vigor index decreased with an increasing PEG-6000 concentration. When the PEG-6000 concentration corresponded to -0.06 MPa, the root growth and fresh weight accumulation of oat seedlings were significantly promoted; however, as the concentration increased to -0.53 MPa and -0.79 MPa, seed germination and seedling growth were significantly inhibited. (3) pH treatments had no significant effect on oat seed germination, but all growth indexes of oats showed a downward trend under alkaline conditions. These results suggest that suitable conditions for oat planting in karst rocky desertification areas are 5 mM CaCl₂, pH levels of 5-8, and drought stress between 0 and -0.32 MPa. This study provides a theoretical basis for oat introduction, cultivation, and stress-resistant breeding in this area.