Auxiliary methods to enhance the survival rate of transplanting test-tube seedlings have become increasingly important in recent years. With the widespread application of rapid propagation techniques, a growing number of plant species and varieties are being cultivated in vitro. However, the climatic conditions and available equipment vary significantly across regions, leading to numerous challenges during the transplanting process. As a result, various techniques and strategies have been developed to improve the success rate of transplanting.
One key issue is the susceptibility of test-tube seedlings to wilting and death due to their weak root systems. This often occurs because the roots may not be well connected to the vascular system of the stem, resulting in poor water and nutrient absorption. To address this, several effective measures can be applied.
Firstly, promoting the recovery and functional development of test-tube seedlings is crucial. Some plants struggle to develop strong roots within the test tube, or their roots do not properly connect with the stem, which limits their ability to absorb nutrients. After transplanting, these seedlings may fail to survive. Even if they do, their chlorophyll content is typically low, as measured by a chlorophyll meter. In such cases, external rooting methods are recommended.
(1) Micro-cutting: Some plants can be propagated using shoots from test tubes as micro-cuttings. These can be directly planted into soil for rooting, though it’s advisable to use hormone treatments for better results. For example, rhododendron cuttings tend to root well both inside and outside the test tube. Some labs have found that inducing root formation in test tubes accounts for 35% of the total cost. However, transplanting rootless seedlings often leads to high mortality. Using an external rooting method allows for combining the rooting and acclimatization phases, reducing costs and improving survival rates.
(2) Rooting in a controlled chamber: A rooting chamber without agar or sucrose can be used, filled with breathable and moisture-retentive substrates like peat, perlite, or moss. Temperature and light are manually controlled, and misting systems help maintain high humidity without wetting the foliage. Cuttings are placed in the chamber and after 3–4 weeks, well-developed roots form, making them easier to transplant into greenhouses. While this method is effective and controllable, it requires higher investment and space.
(3) Transplanting with early root primordia: When test-tube seedlings have just started to form root primordia, they are more resilient and suitable for transport. If roots are too long, they are prone to damage during handling, lowering survival rates. By cutting strong buds at least 3 cm in length and placing them in a rooting medium, new roots typically appear within 7–10 days. After 5–6 days, root hairs develop, enhancing nutrient absorption. This approach improves survival rates, shortens the production cycle, and is ideal for long-distance transport.
(4) Bottle or pot insertion: Seedlings can be inserted into bottles or pots containing a mix of peat, humus soil, and fine sand. About 20–30 rootless seedlings per container are planted at a depth of 0.3–1.2 cm. Adding half-strength MS mineral elements and a rooting solution (IAA at 1.0–5.0 mg/L) helps promote root growth. Cultivated under controlled temperature, humidity, and light conditions, new roots typically appear after 20 days, with secondary roots reaching 8–12 cm after 30 days. More information on chlorophyll meters can be found here: Chlorophyll Meter.
One key issue is the susceptibility of test-tube seedlings to wilting and death due to their weak root systems. This often occurs because the roots may not be well connected to the vascular system of the stem, resulting in poor water and nutrient absorption. To address this, several effective measures can be applied.
Firstly, promoting the recovery and functional development of test-tube seedlings is crucial. Some plants struggle to develop strong roots within the test tube, or their roots do not properly connect with the stem, which limits their ability to absorb nutrients. After transplanting, these seedlings may fail to survive. Even if they do, their chlorophyll content is typically low, as measured by a chlorophyll meter. In such cases, external rooting methods are recommended.
(1) Micro-cutting: Some plants can be propagated using shoots from test tubes as micro-cuttings. These can be directly planted into soil for rooting, though it’s advisable to use hormone treatments for better results. For example, rhododendron cuttings tend to root well both inside and outside the test tube. Some labs have found that inducing root formation in test tubes accounts for 35% of the total cost. However, transplanting rootless seedlings often leads to high mortality. Using an external rooting method allows for combining the rooting and acclimatization phases, reducing costs and improving survival rates.
(2) Rooting in a controlled chamber: A rooting chamber without agar or sucrose can be used, filled with breathable and moisture-retentive substrates like peat, perlite, or moss. Temperature and light are manually controlled, and misting systems help maintain high humidity without wetting the foliage. Cuttings are placed in the chamber and after 3–4 weeks, well-developed roots form, making them easier to transplant into greenhouses. While this method is effective and controllable, it requires higher investment and space.
(3) Transplanting with early root primordia: When test-tube seedlings have just started to form root primordia, they are more resilient and suitable for transport. If roots are too long, they are prone to damage during handling, lowering survival rates. By cutting strong buds at least 3 cm in length and placing them in a rooting medium, new roots typically appear within 7–10 days. After 5–6 days, root hairs develop, enhancing nutrient absorption. This approach improves survival rates, shortens the production cycle, and is ideal for long-distance transport.
(4) Bottle or pot insertion: Seedlings can be inserted into bottles or pots containing a mix of peat, humus soil, and fine sand. About 20–30 rootless seedlings per container are planted at a depth of 0.3–1.2 cm. Adding half-strength MS mineral elements and a rooting solution (IAA at 1.0–5.0 mg/L) helps promote root growth. Cultivated under controlled temperature, humidity, and light conditions, new roots typically appear after 20 days, with secondary roots reaching 8–12 cm after 30 days. More information on chlorophyll meters can be found here: Chlorophyll Meter.
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