Nitrogen absorption by field-grown tea plants (Camellia sinensis) in winter dormancy and utilization in spring shoots

Abstract

The information of nitrogen uptake by subtropical, ever-green broad-leaf plants at cold temperatures of winter is very limited. The present field experiment was conducted to investigate whether 15N is taken up by tea (Camellia sinensis L.) plants in winter dormancy in the absence of active shoot growth and utilization in young spring shoots. We applied 15N-labeled urea to soil at five different times i.e. mid-January, early February, mid-February, and early and mid-March. 15N abundance was determined in fibrous roots, twigs and mature leaves after 3, 7 and 15 days after application and in young shoots the following spring. 15N was taken up by fibrous roots and transported to above-ground tissues within 3 days after application under low winter temperatures. Earlier application significantly increased nitrogen derived from 15N-urea (Ndff) and 15N amount in young spring shoots. Ndff values and 15N amount in young spring shoots were described well by quadratic or linear regressions against soil growing degree days (GDD, T ≥ 8 °C, depth 20 cm) between 15N application and harvesting dates (R2 = 0.58–0.90, p < 0.001). Nitrogen was absorbed and translocated in dormant tea plants in the absence of active root and shoot growth throughout the late winter until early spring. Absorbed N was stored and remobilized to support shoot growth the following spring. Soil GDD between N application and harvesting could predict Ndff and 15N amount in young spring shoots.