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Plant growth in a controlled environment system is highly dependent on the availability of light. The light-emitting diode (LED) is capable of providing the needed quality and quantity of light for the plant. The purpose of this study was to determine the effect of white LED light intensity on the growth of in vitro propagated apple (M-9) seedlings in a controlled environment system. Seedlings were grown for 30 days under five different white LED light intensities: 100–500 (L1), 250–500 (L2), 500–500 (L3), 250–250 (L4), and 100–100 (L5). Our findings indicate that seedlings treated with L3 grew substantially taller than seedlings treated with L1, L2, or L5. The number of leaves, stem diameter, shoot fresh weight, root fresh weight, and shoot dry weight of L3 treated seedlings were considerably greater than those growing in other treatments. Furthermore, root length, root dry weight, chlorophyll content, and photosynthesis rate were considerably increased in the L3 treatment group compared to the L5 treatment group. However, there was no significant difference in the stomatal conductance or transpiration rate of apple seedlings between the light treatments. Moreover, a positive correlation was seen between stomatal conductance and transpiration rate. These results suggest that light intensity PPFD 500-500 were favorable for the initial growth of in vitro propagated apple seedlings.

Substrate composition and container size are considered crucial for apple rootstock grown in a plug seedling system. This study investigated the effect of substrate material’s proportion and different container volumes on the growth of apple rootstock (M-9) plants propagated by tissue culture. In substrate composition, three different ratios of peat moss (PM): vermiculite (VL): perlite (PL) at 1:1:1 (S1), 1:2:3 (S2), 3:1:2 (S3) were used. For container size, plants were grown in 1000 mL (C1), 500 mL (C2), and 300 mL (C3) containers filled by 1:1:1 mixture of PM, VL and PL. In both cases, plants were treated eleven weeks in a green house. Our results demonstrate that the plant height, number of leaves, leaf area, shoot fresh weight and root fresh weight of apple rootstock were significantly higher in substrate composition S3 compared with S1 composition. However, chlorophyll content (SPAD) and photosynthesis rate were unaffected by variation of substrate composition. Furthermore, rootstock grown in C1 container showed plant height, number of leaves, leaf area, number of nodes, root length, shoot and root’s fresh and dry weight were significantly higher than those grown in C2 and C3 volume containers. The chlorophyll content and transpiration rate were not significantly affected by the different container volumes. These results suggest that the substrate ratio 3:1:2 of PM:VL:PL and container size 1000 mL were more favorable than other treatments for initial growth and development of the tissue culture propagated apple rootstock plants.

Centella asiatica is a herbaceous plant containing medicinal and cosmetic properties: anti-bacterial, anti-aging, memory enhancing and wound healing. The lack of information impedes the development of suitable growth conditions for C. asiatica in the hydroponic system. Maintaining proper electrical conductivity (EC) of a nutrient solution is considered crucial for plant growth and the accumulation of bioactive compounds in a plant grown in hydroponics. This study aimed to investigate an optimal EC that enhances the growth of C. asiatica and its centellosides content. Seedlings were grown in commercial nutrient solution and treated with four different strengths of EC (0.6, 1.2, 1.8 and 2.4 indicated T1, T2, T3 and T4, respectively) under controlled environment conditions. Our results demonstrate that the number of leaves, leaf area, number of runners, shoot fresh weight and shoot dry weight were significantly increased in T2 among the treatments. However, these growth parameters were lowest in T4. Furthermore, the content of asiaticoside, madecassoside, asiatic acid and madecassic acid was the highest in plants that were treated with T2. The expression of centelloside biosynthesis-related genes is also affected by the strength of the nutrient solution. A positive correlation was observed between the number of leaves, leaf area and centellosides content. This study provides valuable background on optimal EC content in the nutrient solution in a hydroponic system with enhanced centellosides content to leverage the C. asiatica production.