Application of Salicylic Acid Derivative in Modifying the Iron Nutritional Value of Lettuce (Lactuca sativa L.)

The present experiment addressed the effects of foliar sprays of different iron (Fe) concentrations (mg L-1), i.e., 2.8 (Fe I), 4.2 (Fe II), and 5.6 (Fe III), as well as an ionic derivative of salicylic acid (iSal) in two doses (10 and 20 mg L-1) on lettuce yield, chlorophyll and carotenoids content, and fluorescence parameters. Chemicals were used individually and in combinations two times, 23 and 30 days after the plants were transplanted. This experiment was carried out in a climate chamber. The Fe and iSal applications generally (except Fe I iSal, 10 mg L-1; Fe I iSal, 20 mg L-1; and Fe III iSal, 20 mg L-1) did not influence the fresh and dry matter content. The concentration of chlorophylls and carotenoids was reduced for all treatments in comparison to the control (without spraying). The Fe content in leaves was promoted in the Fe-treated plants (+70% for Fe III + iSal, 10 mg L-1, and Fe I). The iSal treatment promoted the Mn content. For most combinations, the Zn and Cu accumulations, as well as the fluorescence parameters, decreased after the foliar spray applications. Overall, our study revealed the effectiveness of Fe-DTPA chelate, but not iSal, in increasing the Fe content of lettuce grown in soilless cultivation systems.

Morphological and Photosynthetic Parameters of Green and Red Kale Microgreens Cultivated under Different Light Spectra

Microgreens are plants eaten at a very early stage of development, having a very high nutritional value. Among a large group of species, those from the Brassicaceae family, including kale, are very popularly grown as microgreens. Typically, microgreens are grown under controlled conditions under light-emitting diodes (LEDs). However, the effect of light on the quality of grown microgreens varies. The present study aimed to determine the effect of artificial white light with varying proportions of red (R) and blue (B) light on the morphological and photosynthetic parameters of kale microgreens with green and red leaves. The R:B ratios were for white light (W) 0.63, for red-enhanced white light (W + R) 0.75, and for white and blue light (W + B) 0.38 at 230 µmol m-2 s-1 PPFD. The addition of both blue and red light had a positive effect on the content of active compounds in the plants, including flavonoids and carotenoids. Red light had a stronger effect on the seedling area and the dry mass and relative chlorophyll content of red-leaved kale microgreens. Blue light, in turn, had a stronger effect on green kale, including dry mass. The W + B light combination negatively affected the chlorophyll content of both cultivars although the leaves were significantly thicker compared to cultivation under W + R light. In general, the cultivar with red leaves had less sensitivity to the photosynthetic apparatus to the spectrum used. The changes in PSII were much smaller in red kale compared to green kale. Too much red light caused a deterioration in the PSII vitality index in green kale. Red and green kale require an individual spectrum with different proportions of blue and red light at different growth stages to achieve plants with a large leaf area and high nutritional value.

The effect of radiation of LED modules on the growth of dill (Anethum graveolens L.)

Light quality is thought to affect the growth and development of plants. We examined how light influences the growth and content of some chemical compounds in dill (Anethum graveolens L.). The plants were grown under different light quality. The share of orange and green light in the spectrum was constant and amounted to 10% for either colour. In the first combination (A, 70/10), there was 70% of red light and 10% of blue light. Other combinations had the following proportions: B 60/20, C 50/30, D 40/40 and E 30/50 of red and blue light. The PPFD was about 155 μmol m-2 s-1. Blue light inhibited the elongation growth as well as leaf area. It had positive influence on the accumulation of dry mass, glucose and fructose in the herb. In the combinations with higher percentage of red light the plants were characterised by higher content of essential oils, macronutrients and zinc. To sum up, we can say that the proportion of red and blue light has significant influence on the morphological qualities, chemical composition and dynamics of photosynthesis in these plants. On the other hand, the selection of spectral composition of LEDs will depend on the result we want to achieve.