Articles
Reflective materials and biostimulants for anthocyanin synthesis and colour enhancement of apple fruits: visualization, abaxial and adaxial leaf light reflection
Article number
1346_4
Pages
27 – 34
Language
English
Abstract
Fruit coloration in apple and other fruits is one of the main reasons for consumer acceptance.
The increasing use of hail nets, insufficient light exposure, low solar angle and warm temperatures in autumn cause poor coloration, especially in late ripening cultivars.
This study aimed to compare the potential for fruit quality improvement in terms of coloration, firmness, sugar content and starch breakdown using a reflective ground cover and a biostimulant.
The reflective ground cover Lumilys® was spread between rows of Braeburn Mariri Red, apple trees on M.9 under a pearl hail net ca. 4 weeks before anticipated harvest; other apples were treated twice with the biostimulant, Sunred®. The reflective ground cover increased the reflected light by 1.5 to 3.8 times on a sunny autumn day and 1.6 to 3.9 times on an overcast day 1.0 m above ground.
This improved peel coloration, especially in the lower inner part of the canopy, accelerated starch breakdown and increased fruit uniformity without affecting fruit firmness.
The biostimulant, Sunred®, retarded starch breakdown without affecting coloration, firmness and sugar.
The lower (abaxial) light green side of apple leaves reflected 4-5 times more light (max 26%) than the upper (adaxial) dark green side (5-7%), measured perpendicular (90°) to the leaf surface.
Moreover, light reflection almost doubled when diffuse light reflection was measured at a 45° angle with a peak of 27% for the upper and 70% for the lower leaf surface at 555-565 nm and a chlorophyll a trough at 666-671 nm.
Overall, the larger diffuse light reflection from the apple leaves suggests that the beneficial effect of reflective mulches, such as Lumilys®, are due to two modes of action.
The first one is the direct reflection of diffuse light from the reflective mulch in the alleyway to the (apple) fruit.
The second is through secondary light reflection of these light beams from the alleyway onto the abaxial leaf, which has not been reported before to our knowledge, and a step forward in biotechnology and understanding the underlying optical pathways.
The increasing use of hail nets, insufficient light exposure, low solar angle and warm temperatures in autumn cause poor coloration, especially in late ripening cultivars.
This study aimed to compare the potential for fruit quality improvement in terms of coloration, firmness, sugar content and starch breakdown using a reflective ground cover and a biostimulant.
The reflective ground cover Lumilys® was spread between rows of Braeburn Mariri Red, apple trees on M.9 under a pearl hail net ca. 4 weeks before anticipated harvest; other apples were treated twice with the biostimulant, Sunred®. The reflective ground cover increased the reflected light by 1.5 to 3.8 times on a sunny autumn day and 1.6 to 3.9 times on an overcast day 1.0 m above ground.
This improved peel coloration, especially in the lower inner part of the canopy, accelerated starch breakdown and increased fruit uniformity without affecting fruit firmness.
The biostimulant, Sunred®, retarded starch breakdown without affecting coloration, firmness and sugar.
The lower (abaxial) light green side of apple leaves reflected 4-5 times more light (max 26%) than the upper (adaxial) dark green side (5-7%), measured perpendicular (90°) to the leaf surface.
Moreover, light reflection almost doubled when diffuse light reflection was measured at a 45° angle with a peak of 27% for the upper and 70% for the lower leaf surface at 555-565 nm and a chlorophyll a trough at 666-671 nm.
Overall, the larger diffuse light reflection from the apple leaves suggests that the beneficial effect of reflective mulches, such as Lumilys®, are due to two modes of action.
The first one is the direct reflection of diffuse light from the reflective mulch in the alleyway to the (apple) fruit.
The second is through secondary light reflection of these light beams from the alleyway onto the abaxial leaf, which has not been reported before to our knowledge, and a step forward in biotechnology and understanding the underlying optical pathways.
Publication
Authors
S. Haaf, B. Althaus, A. Kunz, M. Blanke
Keywords
apple (Malus × domestica Borkh.), biostimulant, light reflection, light spectrum, diffuse light, Lumilys®, Sunred®
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