Spiking and Flowering of the Phalaenopsis. Part I. Spiking technique

Transcription

1 Spiking and Flowering of the Phalaenopsis Part I. Spiking technique The spiking and flowering technique are the key technique for the Phalaenopsis industry. The flowering time is so important to obtain the high benefit. That is, the blossoms of orchids need to be sold in time. So the quality and timing of flowers are the basic requirement for the orchids growers. What is the basic principle of spiking? The orchids was induced from the vegetative phase to the reproductive phase. There are two basic conditions for the Phalaenopsis: 1.The plant has reached the mature stage, 2.The plant is treated with physiological stress. The above conditions only called the rules not the law. The numeric values of the rules are affected by varieties. For example, cooling temperature is the important factor for spiking. The required cooling day temperature is 25 for amabilis and 20 for P. Fortune Saltzman. The mature stage is also different for all kinds of varieties. Some varieties could be induced to spiking at the culture period of six or eight months after deflasking. Some varieties required fourteen months to reach mature stage. The adequate programming of the Phalaenopsis from the mature plants to flowering is listed in Table 1. The spiking technique is introduced in the following contents. The basic factor affecting the spiking of Phalaenopsis is the genetic characteristics. The environmental control and the management are other key points for the spiking technique. A. Environmental stress The important environmental factors for orchids culture included the day and night temperature, relative humidity, light intensities and period. The proper humidity level ranged from 50 to 80% RH. If the humidity is too low (less than 50% RH) or too high (higher than 90%) and without ventilation, the humidity could have the significant effect on the plants. In most cases, the humidity in the greenhouse could be controlled within the 1

2 adequate range. The environmental stresses are controlled by the setting of temperature and light. 1. Temperature The cooling temperature has the significant effect on the spiking. However, the setting temperature of day and night temperature are affected by the variety s characteristics. The spiking percentage is a function of the accumulated cooling temperature. The larger of the difference between the growing and cooling temperature, the shorter of the spiking period. That is, get the day and night temperature be lower could enhance the spiking. However, the endurance of the low temperature needs to be considered. Some varieties are sensitive to the lower temperature. If the cooling temperature is too low for this variety, these plants are easy damage by the cooling treatment. Some varieties are grown well at higher day and night temperature and it very easy to induce two spikes by lowing day and night temperature (for example, 18 ). Some varieties, such as amabilis, are cultured at high day temperature (27-30 ) and medium night temperature (20-23 ). These varieties only could be induced to spiking by cooling day temperature. The environment factors of different stages for several Phalaenopsis varieties are listed in Table Light intensity and period In the cooling stage, the temperature is kept at lower range, so the photosynthesis rate is decreased. These plants need to be supplied more light intensity to compensate the temperature factors and to accumulate the enough dry matters, especially carbon source. The recommend light intensity is listed in Table 2. The optimum light period is 14 hours. The light period could be maintained in the range of 12 to 16 hours. If the natural day light period is less than 12 hours, the artificial light needs to be applied to extend the light period. 2

3 B. Management The management included the watering, fertilizing, and hormones applying. The relationship between the spiking and fertilizing could be explained from the principle of Plant Physiology. The increase of the ratio of C/N of the plant could help the change of plants from vegetable stage to reproducible stage. Two ways can be adopted to increase the carbon sources: increase temperature and light intensity level. The reduction of N source could be applied by decreasing the N source and increase others fertilizer components. The pretreatment of spiking could be executed at one month before change the setting temperature environment for cooling. The useful technique is to increase the temperature and light intensity in the greenhouse, decrease the N concentration and increase the P and other components. It worth mentioning that the fertilizing ratio should not be exchanged abruptly. The spiking period is ranged from four to eight weeks. The fertilizing formula could be applied in the order of (N-P-K) and (N-P-K) interchangeability. The application of hormones is not a good ideal. The concentration of hormones is not easy to control. If the concentration is too high, the shape of flower could be changed unpredictably. To use the hormones only have the small effect on the spiking. However, the application of hormones with the cooling stress could increase the spiking percentage and shorten the cooling period. The adequate hormones levels are influenced by the characteristics of varieties. C. The abnormal physiological stress Some abnormal physiological stresses could induce the spiking. However, due to the abnormal stress, the plants may be damaged and the flower quality is poor. The abnormal stress included: 1. No water supply or the water quantity is not enough. 3

4 2. Root damage, the roots are injured at the transplanted or transported process. 3. The abrupt change of temperature, it could be expressed as the change rate of air temperature to the time. If the temperature change rate is higher than a criteria value, the temperature stress could induce the stress and spike is found. Two common conditions are found in the subtopic region for this abnormal stress. 1. Force ventilation in winter In winter, the greenhouse temperature always maintained at higher level for the growing requirement of Phalaenopsis. The outside air temperature is low due to the cold current or at night time. The mechanical ventilation was operated at the fixed interval period. If the cold air was sucked into greenhouse suddenly, the temperature change rate is pretty high. It is very easy to induce the spiking in this case. 2. The air temperature decreased rapidly in summer The rain storm is a common condition in summer. The air temperature decreased rapidly and the cooler air was inhaled into greenhouse by the exhaust fans. The temperature change rate induced the spiking. As the outside temperature is back to the warm state, the high air temperature was inhale into greenhouse and exist the cooler air. The change pattern of air temperature induced the spiking and easy to damage the plants. In the literature of Anthurinfo, they mentioned that the influence of the temperature for blooming is around 60%, light is at 30% and other factors at 10%. This ratio may be different for the setting values of greenhouse environment, different management technique and various varieties. From the above discussion, several factors could be combined to induce the spiking. The optimum technique controlled by the growers is to create the stress environment and avoid the damage of the plants. 4

5 Table 1. The programming of the Phalaenopsis from mature plants to flowering Operation stages Physiological reaction 1. Environment : Optimum conditions 2. Fertilizing, Formula A (N-P-K) Ⅰ. Growing stage 1. Plant: mature enough 2. Dry materials: accumulation enough 3. Roots: healthy 1. Increase day temperature, Increase light intensity 2. Increase P, reduce N, Ⅱ. Pretreatment stage 1. Increase of the dry matter accumulated at the leaves and stems Formula B (N-P-K) 1. Decreasing temperature, Increasing light level Ⅲ. Spiking 1. Changes in endogenous levels of plant hormones 2. Interchangeability of Formula A and B 3. No hormones application 4. Abnormal stress also enhance spiking 1. Increase temperature, light level is normal or a little higher than normal level 2. Fertilizing, Formula A (N-P-K) Ⅳ. Spike extending 1.The carbon is produced by photosynthesis at leaves 2. The carbon source is transported from leaves to spikes 1. Reduce temperature, light level is At normal level 2. Fertilizing, Formula A Ⅴ. Flowering 1. The carbon is produced by photosynthesis at leaves and then transported to spikes, buds and flowers. 2. UV-B is required to enhance the bright color of flowers. 5

6 Table 2. Environmental factors of different stage for several Phalaenopsis varieties Data sources: Big white Small white Culture Guide V3 Hsin-Yen Fortune Queen of Floricultura b.v. amabilis Beauty Saltzman Beer Ⅰ. Growing 1.T dg Stage 2.T ng lux lux Ⅱ. 1.T dp pretreatment 2.T np lux lux lux lux Ⅲ. spiking 1.T dc T nc lux lux lux Ⅳ. Spike 1.T de extending 2.T ne lux lux Ⅴ. 1.T db Blossoming 2.T nb lux lux Note: 1. The growing temperature at day and night, T dg, T ng. 2. The pretreatment temperature at day and night, T dp, T np. 3. The cooling temperature at day and night, T dc, T nc. 4. The spike extension temperature at day and night, T de, T ne. 5. The blossoming temperature at day and night, T db, T nb. 6

7 About the author: Professor Chiachung Chen, Ph. D. Biosystems Engineering Laboratory National ChungHsing University 250 KuoKuang Rd., Taichung, Taiwan Tel: , Fax: Web site: bse.nchu.edu.tw 7