Effects of Nutrient Deficiency on Root Morphology and Nutrient Allocation in Pistacia chinensis Bunge Seedlings

Plant growth depends on soil mineral elements, a lack of which results in reduced nutrient accumulation leading to poor growth and resistance in plants. Therefore, more information is needed about the response of Pistacia chinensis Bunge (P. chinensis) seedlings to nutrient deficiency. In this study, we investigated how soil nutrient availability affects the nutrient accumulation and root system of P. chinensis seedlings. Seedlings were cultivated under five different nutrient treatments (500 mg, 400 mg, 300 mg, 200 mg, and 100 mg N). Various indices, including seedling growth, nutrient accumulation and root morphology, were analyzed at the end of the growing season. Nutrient deficiency (300 mg, 200 mg, and 100 mg N) reduced the accumulation of nitrogen (N), phosphorus (P) and potassium (K) in roots and stems, while the nutrient proportion of N, P, and K stored in the roots and root to shoot ratio (R/S) was increased at the end of growing season. Root length, root surface area, and root volume of very fine roots (<0.5 mm in diameter) and coarse roots (>3.0 mm in diameter) of the three lower nutrient treatments were significantly lower than those of the two highest nutrient treatments, while no significant difference was detected in the fine roots (1.0-3.0 mm in diameter). Instead, foliar N and K contents in seedlings treated with the two highest treatments were significantly greater than those of the three lower nutrient treatments, resulting in a greater nutrient loss ratio. However, seedlings treated with 100 mg N had significantly higher foliar P content than those treated with 500 mg. Seedlings treated with 300 mg and 200 mg N did not have restricted root nutrient accumulation but did have reduced nutrient accumulation in the stems. The 100 mg N treatment significantly reduced the root nutrient accumulation of N and K. The 500 mg N treatment did not increase the accumulation of nutrients in the storage organs compared with the 400 mg N treatment, but did increase the loss of N and K due to defoliation in autumn. In conclusion, there is a threshold for nutrient accumulation in storage organs at the nursery stage under a specific environment. P. chinensis seedlings reduced the negative effects of nutrient deficiency by promoting root growth, particularly fine roots, and increasing N and K allocation in storage organs.