Indicators of nitrogen status for ornamental woody plants based on optical measurements of leaf epidermal polyphenol and chlorophyll contents

• Published in: Scientia horticulturae 2008, Vol.115 (4), p.377-385
• Main Authors: Demotes-Mainard, Sabine, Boumaza, Rachid, Meyer, Sylvie, Cerovic, Zoran G.
• Format: Article
• Language: English
• Subjects: Agricultural sciences; Agronomy. Soil science and plant productions; Biological and medical sciences; Callicarpa bodinieri; chlorophyll; dry matter partitioning; Dualex; epidermis (plant); Fundamental and applied biological sciences. Psychology; Horticulture; image analysis; Lagerstroemia indica; leaves; Life Sciences; nitrogen; Nitrogen nutrition indicator; nursery crops; nutrient content; nutritional status; optical properties; Ornamental plants; ornamental woody plants; plant growth; plant nutrition; polyphenols; SPAD; Viburnum tinus
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/j.scienta.2007.10.006

Indicators of plant nitrogen (N) status adapted to woody ornamental plants are essential for the adjustment of fertilization practices in nurseries. The objective of this study was to investigate whether optical measurements of leaf epidermal polyphenol (EPhen) and chlorophyll (Chl) contents could be used as N status indicators for woody deciduous and evergreen ornamental plants. One-year-old plants of Lagerstroemia indica, Callicarpa bodinieri and Viburnum tinus were grown outdoors in containers. They received low (TN 1, 4 mg L −1) or high (TN 2, 105 mg L −1) levels of N during 2 months in spring and summer. TN 1 treatment limited shoot growth from 28 to 37 days after treatment initiation in Lagerstroemia and Callicarpa, respectively . Shoot growth was unaffected until day 176 in Viburnum. The mass-based leaf N content (N M) of a sample of young expanded leaves exposed to direct sunlight was tightly correlated with shoot N content and differentiated treatments several weeks before shoot growth reduction for the three species. N M was therefore used as an index of plant N status. EPhen and Chl contents were recorded with Dualex™ and SPAD-502 leaf-clip meters, respectively. Dualex values were strongly and negatively correlated with N M, and differentiated the treatments early in the experiment, in all three species. SPAD values were positively correlated with N M for Lagerstroemia and Callicarpa, but not for Viburnum, because large variations in leaf mass per area (LMA) in this species compensated for variations in leaf dry mass invested in Chl. The SPAD/Dualex ratio was used to assess changes in the proportion of leaf dry mass allocated to proteins and polyphenols in response to fertilization. It differentiated between the treatments early in the experiment and was correlated with N M in all three species.