Effects of micronized calcite, hoagland solution and Ascophyllum nodosum extract on acclimatization and vegetative growth of in vitro-derived Phalaenopsis spp.

Orchids (Orchidaceae) have high economic value both as ornamental plants and for their uses in the food, perfume, and pharmaceutical industries.However, due to the lack of endosperm in their seeds and their late germination, micropropagation techniques are of great importance. The most critical stage limiting the development of orchid plantlets produced under in vitro conditions is acclimatization, the transition process from the laboratory environment to the external environment. This study was conducted to determine the effects of seaweed (Ascophyllum nodosum), micronized calcite (Herbagreen), and Hoagland solution applications on increasing the survival rates and growth parameters of Phalaenopsis spp. orchids during the acclimatization stage. In the study, parameters such as plantlet survival rate, number of leaves, plant height, SPAD (chlorophyll content), leaf width and size were examined on 30, 60, 90, and 120 days after treatment (DAT). According to the results of the statistical analysis, significant differences were found between the applications in all examined growth parameters (p<0.05). The survival rate was 100% in all experimental groups, and the acclimatization process was successfully completed. The separate application of micronized calcite and hoagland solution showed superior results in terms of plant height growth compared to the control group. In terms of chlorophyll content (SPAD), the Seaweed+Micronized calcite+Hoagland combination provided the highest chlorophyll accumulation in measurements taken on day 60. In conclusion, it was observed that the applications of seaweed, hoagland solution, and micronized calcite supported the vegetative development of orchid seedlings during the acclimatization phase and increased their stress tolerance. These findings offer a practical application protocol for reducing losses during the adaptation process of plantlets to the external environment and producing higher quality plants in in vitro orchid production.