با همکاری انجمن علمی منظر ایران
نوع مقاله : مقالات پژوهشی
نویسندگان
1 گروه علوم باغبانی- دانشکده کشاورزی- دانشگاه زنجان
2 گروه علوم باغبانی، دانشکده کشاورزی، دانشگاه زنجان، ایران
کلیدواژهها
عنوان مقاله English
نویسندگان English
Extended Abstract
Introduction
The skin color of apples is one of the key determinants of their marketability and economic value, primarily influenced by the accumulation of anthocyanin pigments. These compounds not only enhance the visual appeal of the fruit but also contribute significantly to its nutritional and antioxidant properties. Numerous studies have indicated that balanced tree nutrition plays a crucial role in anthocyanin biosynthesis and color development. Foliar application of nutrients is considered an efficient approach to overcome soil-related limitations in nutrient uptake. However, the low efficiency and environmental impacts of chemical fertilizers have prompted increasing interest in sustainable biostimulants. Biofertilizers such as seaweed extract, humic acid, and amino acids can stimulate physiological processes and improve nutrient absorption, offering an eco-friendly alternative. These biostimulants enhance apple coloration and quality while mitigating adverse environmental effects. This study was conducted to evaluate the impact of foliar application of selected biofertilizers compared to a chemical fertilizer containing nitrogen, zinc, and boron on anthocyanin content and colorimetric traits of ‘Red Delicious’ apples under the climatic conditions of Zanjan province.
Materials and methods
The field experiment was conducted during the 2023 growing season in a commercial apple orchard. The study was arranged in a Randomized Complete Block Design with three replications. The experimental treatments included foliar application of seaweed extract (0.075% and 0.15%, Alg), amino acids (0.1% and 0.2%, GF Amino), humic acid (0.03%, HA), the commercial fertilizer Homarang (0.5%, Homafert), a combined chemical fertilizer containing nitrogen, zinc, and boron (1% urea, 0.3% zinc chelate, and 0.1% boric acid, Combinate fert), and distilled water spray as the control. Each experimental unit consisted of three uniform trees. The foliar application of treatments began 40 days after full bloom and was repeated three times at 30-day intervals until the physiological maturity of the fruits. Fruits were harvested at the physiological maturity stage (130 days after full bloom) based on the fruit growth curve. Ten fruits were randomly selected from each experimental unit and transferred to the laboratory for the measurement of the anthocyanin, chlorophyll, carotenoid pigment contents, colorimetric indices, PAL enzyme activity, and the content of nutrient elements in the apple fruits.
Results and Discussion
The results showed that the highest fruit skin anthocyanin content was obtained with the application of Hamafert representing a 137.92% increase compared to the control. The highest ratio of anthocyanin content to the sum of chlorophyll and carotenoids was achieved in the HA treatment, showing a 252.28% increase compared to the control, which indicates a more effective activation of the red pigment production pathway. The Combinate fert caused a slight increase in total chlorophyll content 51.16% compared to the control but resulted in the lowest relative anthocyanin content, representing a 38.89% decrease relative to the control. The highest PAL enzyme activity was observed in fruits treated with Hamafert, an increase of 139.43% compared to the control. Colorimetric indices showed that all bio-fertilizers significantly increased redness, but Hamafert recorded the highest total color index (79.58%) increase in the redness index compared to the control. The lowest total color index was obtained with the Combinate fert (64.39% decrease in the redness index compared to the control). Significant positive correlations were observed between anthocyanin content and nutrient elements such as phosphorus (r=0.68), iron (r=0.66), boron (r=0.63), and zinc (r=0.44) in the fruit. Mineral analysis revealed that biostimulant treatments, particularly ‘Homafert’ and HA, enhanced the fruit's uptake of specific micro-elements. This underscores the critical role of a balanced and bioavailable supply of these nutrients, which act as co-factors or regulators in pigment synthesis pathways, beyond the basic nitrogen provision of conventional fertilizers. This study conclusively demonstrates that foliar application of biostimulants is a highly effective and sustainable agronomic strategy for enhancing the critical quality attribute of skin color in ‘Red Delicious’ apples. The commercial biostimulant ‘Homafert’ (0.5%) and HA (0.03%) were particularly outstanding, outperforming Combinate fert.
Conclusion
The biostimulants’ efficacy is mechanistically linked to: 1.The upregulation of PAL enzyme activity, accelerating the flux into the anthocyanin biosynthesis pathway. 2. The improved uptake and assimilation of key mineral co-factors (P, Fe, B, Zn), which are essential for enzyme function and pigment stability. This study conclusively demonstrates that foliar application of biostimulants is a highly effective and sustainable agronomic strategy for enhancing the critical quality attribute of skin color in ‘Red Delicious’ apples. The commercial biostimulant ‘Homafert’ (0.5%) and HA (0.03%) were particularly outstanding, outperforming Combinate fert.
کلیدواژهها English
