An experimental assessment of carbon and nitrogen allocation in Pinus pinea populations under drought stress and rewatering treatment

Abstract

Global drought effects will increase with climate change and, accordingly, plant species will be affected at different scales. Carbon (C) and nitrogen (N) are critical for plant growth and development. Drought stress disturbs the process of adjusting C and N acquisition and allocation in plants. The present study aimed to determine the N (%), C (%), C/N ratio, carbon mass (CM, g), and nitrogen mass (NM, g) in different plant organs (needle, shoot, stem, and root) in 2-years-old stone pine (Pinus pinea L.) seedlings from seven different populations of Türkiye under drought stress and rewatering treatment. The seedlings were subjected to drought until a predawn water potential between − 4.5 MPa to − 4.0 MPa. The return of the seedlings to their pre-drought level was determined by using resistance (RS), recovery (RC), and resilience (RSL) indices. The N concentration in each organ showed significant differences between the populations in response to drought while the C concentration differed between the populations only in roots. In drought, the N (%) and NM (g) values in needles increased in the populations and the increase was 50% higher in northern populations. The N (%) and NM (g) values in shoots increased almost twice in response to drought. Although C (%) and CM (g) decreased in needles and shoots in drought, they increased in stems and roots. The stem C/N ratio increased by more than 100% in some populations in drought. Root C/N ratios increased by more than 50% in drought, while they generally decreased below control values with rewatering. The C/N ratio in the stem showed great resistance and recovery, while resilience stayed negative. In conclusion, stone pine populations generally demonstrated high recovery in terms of N concentration in roots after drought. Compared to northern populations, southern populations showed more resistance to drought in terms of needle and shoot N concentration. The needle and shoot N (%) of northern populations demonstrated high resilience capacity.