Horticulturae, Vol. 11, Pages 1091: Anthocyanin Biosynthesis of White Asparagus Spears in Relation to the Pre-Harvest Exposure to Infrared and Sunlight Radiation

Horticulturae doi: 10.3390/horticulturae11091091

Authors:
Parthena P. Papadopoulou
Eirini A. Siomou
Symeon A. Siomos
Anastasios S. Siomos

Although the presence of anthocyanins in white asparagus is undesirable because it degrades its commercial quality, very little is known about their biosynthesis and regulation. The biosynthesis of anthocyanins in most plants is light dependent, but in white asparagus spears only a few studies have evaluated the effects of light and all of them focus mainly on the post-harvest period. There are no relevant reports on the effects of exposure of spears to solar and infrared radiation during their growth and development. For this purpose, white asparagus spears were grown in the dark under a low tunnel (100 cm wide and 60 cm high) for 7 days before being exposed to sunlight for 0, 2, 3, 4, 5, or 7 h. Subsequently, the spears were either harvested and kept in the dark or continued to grow in the dark for 0, 24, or 48 h. At the end of the treatments, the color and the anthocyanin and total phenol content of the top 7 cm of the spears were determined. The results showed that the infrared radiation that was trapped below the tunnel during the 7-day growing period of white asparagus spears induced anthocyanin biosynthesis only in the lower part (base) of the spears. Exposure to sunlight for at least 3 h was critical for significant anthocyanin biosynthesis in the epidermal cells of the top 7 cm part of white asparagus spears (0.48–0.95 μg g−1 FW). The amount of anthocyanins 24 h later was proportional to the exposure time (y = 0.1585x − 0.162, R2 = 0.9953) and was greater in the spears harvested and kept in the dark (up to 5.67 μg g−1 FW) than in the spears that continued to grow in dark conditions (up to 4.32 μg g−1 FW).

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