Spiking model of the Phalaenopsis

The factor affecting the spiking of Phalaenopsis include day and night temperature, light intensity, fertilization concentration and hormone concentration The quantitative Spiking model of Phalaenopsis is introduced:

I. Illustration of the spiking model

        The spiking percentage is from 0% to 100%; its model is shown as follows:

 Spiking percentage (P) = 100%〔Mature index, 〕

〔Accumulated cooling temperature index, ACT〕^b1

〔Accumulated light intensity, ALI〕^b2

〔Fertilization utilization index, FUI〕^b3

〔Hormone concentration, HC〕^b4                     (1)

1. Mature index,

      The mature index is used to express the maturing conditions. The value of  is from 0 to 1. The numeric value varied by the orchid variety and carbon accumulation. The mini verities can reach 1.0 after 6month’ culture time. Big white varieties require 18 months. With normal culture conditions of temperature, light intensity, fertilization and other factors, the value could equal 1.0.

2. Accumulated cooling index, ACI

   the accumulated cooling index (ACI) index is calculated as follows:

                      (2)

The accumulated cooling temperature (ACT) is used to as an environmental variable. It is calculated by follows:

    (3)

where  is the adequate culture temperature during the day;  is the day-time temperature of the cooling room, H_d is the day period in hours;  is the adequate culture temperature at night;  is the night-time temperature of the cooling room; and H_n is the night period in hours.

3. Accumulative Light Intensity, ALI

        The definition of terms concerning light intensity is as follows:

        : Light intensity in the cooling room,

: Low limitation value of light intensity

: High (endurance) limitation value of light intensity

: Accumulated hours for the light intensity of the cooling room range from  to.

a. If ＜, ALI=0                                                 (4)

b. If ＞, ACI=0                                                (5)

c. If ＜＜,

        ACL=              (6)

         is the light intensity factor.

4. Fertilization utilization index, FUI

The FUI is calculated as follows:

FUI=                                        (7)

where  is the applied quantity of phosphorus;  is the basic requirement of phosphorus;  is the applied quantity of nitrogen, is the basic requirement of nitrogen;  is the applied quantity of other fertilizers; and  is the basic quantity of other fertilizers.

             is the limitation of phosphorus,  is the limitation of other fertilizers. If ＞＞ or ＞, . The  value is from 0 to 1 and is affected by the characteristics of varieties.

5. Hormone concentration

        The safety criterion of the hormone concentration is. If the applied concentration is greater than, the spiking model is meaningless.

II. Application of the spiking model

        Equation (1) could be expressed as follows:

                           (8)

        The parameters of b₁, b₂, b₃ and b₄ represent the effect of temperature, light intensity, fertilization concentration and hormone concentration, respectively.

        In The Netherlands, temperature and light intensity are domain factors. Research by the company Anthura indicated that  and It represents that the effect of temperature is about 60%, light is 30% and other factors are 10%.

        A typical Phalaenopsis variety is cooled in The Netherlands. The typical index is: . After 6 weeks’ cooling, ALI=0.985, FUI=1.0 and HC=1.0.

        The spiking percentage is:

            = 98.05%                                                 (9)

For the Taiwan orchid industry, the cooling temperature is the main factor.

The spiking model used in Taiwan is as follows:

                     (10)

        That is, the temperature accumulation is at 70%, and light intensity has 20% effect, fertilization concentration have 8% effect and for Hormone 2%.

          For the amabilis variety, the index isasfollows:, by equation (10),

Table 1. Environmental factors for different stages of several main

Phalaenopsis varieties

Note: 1. Growing temperature at day and night, T_dg, T_ng.

2. Pretreatment temperature at day and night, T_dp, T_np.

3. Cooling temperature at day and night, T_dc, T_nc.

4. Spike extension temperature at day and night, T_de, T_ne.

5. Blossoming temperature at day and night, T_db, T_nb.

About the author:

Professor Chiachung Chen, Ph. D.

Biosystems Engineering Laboratory
National ChungHsing University

250 KuoKuang Rd.,

Taichung, Taiwan 40227

Tel: 886-4-22857562, Fax: 886-4-22857135

Web site: http://amebse.nchu.edu.tw/orchids_cultivation.htm

Email: ccchen@dragon.nchu.edu.tw