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Spectral properties of cultivation, leaves, and fruits of the aubergine

Marian Czarnowski*, Stanisław Cebula**

**The Franciszek Górski Department of Plant Physiology
**Polish Academy of Sciences
**Sławkowska 17, 31-016 Kraków, Poland
**Department of Vegetable Crops
**Faculty of Horticulture, Agricultural University
**29 Listopada 54, 31-425 Kraków, Poland

The quantum irradiance (GMR) in the midday hours on a sunny day in June measured above the greenhouse aubergine cultivation were equal to 2460 μmol(quantum) m-2 s-1, and in the PAR range 1065 μmol(quantum) m-2 s-1. The spectral transmittance of solar radiation through plant cultivation depends on the weather conditions and the value of the leaf area index (LAI) of the plants. The transmittance through the canopy of the aubergine, in the range GMR, on a sunny day in June reached from 9% at LAI 3.3 to 18% at LAI 1.4, and in the PAR range from 2-8% of the incident radiation on the plants, respectively. This demonstrated the high PAR absorptance of the aubergine plants. The transmittance in the near infrared was from 4 (at LAI 1.4) to 10 (at LAI 3.3) times higher than that in the PAR range.

The quantum irradiance (GMR), reaching the upper surface of the aubergine canopy in a greenhouse on a sunny day in September decreased to a value of about 2050 μmol(quantum) m-2 s-1 [including 880 μmol(quantum) m-2 s-1 of PAR]. In comparison with June, the transmittance of solar radiation through the plant cultivation decreased to a value from about 4% (at LAI 3.1) to 13% (at LAI 2.1), and in the PAR range 2-7%, respectively.

A single leaf of the aubergine plant revealed low reflectance (about 7%), high absorptance (about 88%), and low transmittance (about 5% in the PAR range. In the near infrared the leaves revealed considerable reflectance (about 49%), very weak absorptance (about 5%), and high transmittance (about 46%). This protects the leaves from overheating and also from inhibition of the process of photosynthesis.

Contrary to the reflectance of purple-violet coloured skin (with pericarp, 0.6 mm thick) of the older aubergine fruits being low in the PAR range (5%), in the near infrared it considerably increased to 63%. The skin demonstrated high absorptance of radiation (93%) in the PAR range.

Czarnowski M., Cebula S., 1999. Spectral properties of cultivation, leaves, and fruits of the aubergine. Folia Horticulturae 11/1: 15-28.