ALBERT

Description: 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 (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.

Description: Subirrigation (SI), where water is provided to container seedlings from below and rises through the growing media via capillary action, is regarded as an environmentally-responsible method of delivering water and fertilizer to nursery-grown plants, resulting in more uniform crops and improved production efficiency. While a concern around adopting this method is that a potential higher salt concentration in the upper layers of growing media under SI may inhibit root growth and result in decreased plant quality, few studies have focused on how root morphology is altered by SI. Therefore, a balanced two-factor factorial design with three rates of fertilization (50, 100, and 150 mg N seedling−1) and two irrigation methods (SI or overhead irrigation (OI)) was used to examine the growth response of Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr) seedlings for one nursery season. Associated changes between rhizosphere electrical conductivity (EC) and root morphology of different root size classes were analyzed. Results show that (1) height, root-collar diameter, and root volume were similar between seedlings grown under SI and OI. However, (2) compared to seedlings receiving OI, SI-seedlings had less root mass, length, and surface area but greater average root diameter (ARD). (3) Morphological differences were evident primarily in root diameter size classes I–III (D ≤ 1.0 mm). (4) Fertilizer rate influenced root length and surface area up to 130 days after sowing but affected ARD throughout the growing season such that seedlings treated with 50 mg N had smaller ARD than seedlings treated with 100 mg N. (5) As the growing season progressed, SI-media had significantly higher EC compared to OI-media and EC increased with increasing fertilizer rate under SI but not under OI. These results indicate that SI can produce larch seedlings of similar height and root collar diameter (RCD) compared to OI, but root systems are smaller overall with fewer small-diameter roots, which may be related to high EC levels in SI-media, which is exacerbated by the use of high rates of fertilizer. Therefore, the EC in the media should be monitored and adjusted by reducing fertilizer rates under SI.