Nutrient uptake and utilization in Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr.) seedlings exposed to a combination of light-emitting diode spectra and exponential fertilization

Abstract

ABSTRACT Exponential fertilization (EF) can cause seedlings to load more nutrients than they need to grow to establish reserves. Lighting spectrum adjustment may strengthen the growth and nutrient utilization of seedlings, which may modify seedling response to EF. In this study, containerized Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr.) seedlings were cultured in commercial substrates (275.59 mg nitrogen [N] and 60.05 mg phosphorus [P] per plant) and received EF at 0 (control), low (88 mg N and 36 mg P per plant), and high (130 mg N and 54 mg P per plant) doses under continuous lighting for 18 h daily. Two light-emitting diode (LED) spectra with different red (R), green (G), and blue (B) ratios were used as R-tinted (R7BG1) and G + B-tinted (R3BG10) colours. Under the R7BG1 spectrum, seedlings receiving low-dose EF had the best growth in height of 29 cm (P = 0.0100) and root-collar diameter (RCD) of 4.7 mm (P < 0.0001) and the highest N (170 mg plant−1; P < 0.0001) and P contents (154 mg plant−1; P < 0.0001). These seedlings also had the greatest biomass of leaves (P = 0.0005), stems (P = 0.0062), and roots (P = 0.0016) in the high-dose EF treatment. This combined effect resulted in the highest N uptake efficiency of nearly 40%. High-dose EF increased the chlorophyll-a and -b contents, while light spectra modified leaf protein content. Therefore, the LED spectra had an interactive effect with the EF dose on nutrient uptake and utilization in Prince Rupprecht’s larch seedlings with a recommended regime of EF at 88 mg N and 36 mg P per plant under the R7BG1 LED spectrum.