Effect of soil moisture content and nitrogen fertilizer on survival, growth and some physiological characteristics of Platycladus orientalis seedlings

Abstract

Given the important applications of oriental arborvitae (Platycladus orientalis /L./ Franco), we examined the interaction effects of soil moisture content (SMC) and urea fertilizer on survival, growth and some physiological characteristics of seedlings of this species. In this study, 270 uniform oriental arborvitae seedlings were transplanted in 2 kg containers filled with the top soil of the natural stand in Soorkesh forest reserve. After 2 months, 6 levels of SMC (100%, 75%, 50%, 25%, 15% and 10%) and 3 levels of urea [control: 0, low nitrogen (LN): 75 mg·kg<sup>–1</sup>, and high nitrogen (HN): 150 mg·kg<sup>–1</sup>] were used from June till the end of the first growing season in 3 replications and 5 seedlings per replication as subsamples. The results showed that all seedlings survived under SMC above 25% in control and urea fertilizer treatments. However, under 15% and 10% SMC, the seedling survival decreased significantly in control treatment, but adding urea fertilizer significantly increased the survival, especially in HN treatment. Growth and morphological properties of seedlings, including root and shoot length, number of first-order lateral roots and total biomass, showed a significant decrease at 75%. Seedling quality index gradually decreased with SMC reduction, but the addition of urea to the soil significantly increased it under all SMC treatments. The results also indicated that a decrease in SMC significantly decreased relative water content of leaves and total chlorophyll content, and urea fertilizer increased total chlorophyll under all SMC treatments, but it increased relative water content only at 100% to 25%. Moreover, water use efficiency of P. orientalis seedlings significantly increased under low soil moisture treatments, and urea significantly increased it, especially under HN treatment. In conclusion, urea fertilizer, especially in the higher amount (150 mg·kg<sup>–1</sup>), improved growth and quality of seedlings under different soil moisture conditions, and increased their survival under severe drought.

Lipid Peroxidation, Antioxidant Enzyme Activities, and Osmotic Adjustment in Platycladus orientalis and Amorpha fruticosa Differ during Drought and Rewatering

“…Furthermore, osmoprotectants, such as proline (Pro) and soluble sugars (SS), have been identified as key components in osmotic adjustment, improving drought resistance in a variety of plant species [31,32]. In our study, we found that SOD, POD, and CAT activities, together with Pro and SS contents, increased with both the duration and intensity of water stress, which supports previous findings [17,19] that P. orientalis and A. fruticosa have the ability to adapt to drought stress. However, the W4 treatment resulted in notable decreases in the activities of antioxidant enzymes and the contents of the two osmotic solutes.…”

“…Additionally, A. fruticosa is a nitrogenfixing species and frequently employed as a pioneer species for vegetation restoration in the region [17]. The effects of water stress on P. orientalis and A. fruticosa have been studied in depth in a number of reports [7,15,18,19]. Several of these reports note that these species can survive under these conditions by regulating their antioxidant enzyme activities and biochemical responses.…”

Influence of drought stress and N addition on the gas exchange, biochemical and growth traits in Quercus ithaburensis

“…RWC increases when drought stress is accompanied by N addition (low N supply) and increase of N supply under well-watered conditions. Seedlings need nitrogen to support changes in all their cellular and physiological processes under drought conditions (Aliarab et al, 2020). Drought stress reduces SWC, Ψ (xylem water potential), and RWC (Deligöz & Bayar, 2021).…”