蝴蝶蘭對介質鹽度之生理反應

Abstract

蝴蝶蘭 (Phalaenopsis spp.) 栽培之適宜介質鹽度已有些許研究，但對不同生育階段植株可耐受之鹽度差異卻少有研究。鹽度為溶液中鹽類離子之總合，相同鹽度下，鹽類離子的組成差異亦可能影響蝴蝶蘭生長及養分吸收，但目前相關研究尚不完整。於不適當的鹽度環境可能造成蝴蝶蘭植株之氧化逆境，抗氧化酵素於氧化逆境下活化，以控制植株內活化氧族含量。本研究將探討不同苗期蝴蝶蘭對鹽度的耐受程度，以及於高鹽逆境下蝴蝶蘭如何調控體內抗氧化酵素及抗氧化物質，以減緩活性氧族對植株細胞造成的傷害。 以不同EC值液態肥料栽培蝴蝶蘭小苗 (6公分盆)、中苗 (8.5公分盆) 及大苗 (10.5公分盆)，液態肥料EC值之增加致使介質EC值上升，造成鹽類逆境，抑制蝴蝶蘭植株生長與大苗抽梗率。各苗期能耐受之液態肥料EC值各異，小苗應低於1.15 dS•m-1，中苗應低於2.15 dS•m-1，而大苗應低於3.15 dS•m-1；若欲維持大苗之抽梗表現， EC值應低於2.15 dS•m-1。 以不同EC值及不同鹽類組成之液態肥料栽培蝴蝶蘭中苗，離子間吸收之拮抗作用隨澆灌液態肥料之EC值增加益趨明顯。EC值高於2.15 dS•m-1之液態肥料，限制蝴蝶蘭對鉀離子、鈣離子及鎂離子的吸收。而相同EC值之養液，鈉離子濃度提高，會強化拮抗作用，使蝴蝶蘭對鉀離子、鈣離子及鎂離子的吸收更為困難。 於1/2 MS培養基中添加不同濃度氯化鈉栽培蝴蝶蘭，培養基EC值在3.1 dS•m-1至5.5 dS•m-1之範圍時，蝴蝶蘭培植體均能生長及發根。於培養基中添加0.1 g•L-1的氯化鈉，可促進蝴蝶蘭的生長，植株全株鮮重與乾重均提升。 以不同肥料濃度與不同氯化鈉濃度液態肥料栽培蝴蝶蘭，介質EC值上升會使蝴蝶蘭的根部受到鹽類逆境，根部過氧化氫濃度增加，ascorbate peroxidase (APX)及Catalase活性增加。而若液肥中鈉離子濃度較高，會使植株遭受更大氧化逆境，蝴蝶蘭根部APX及Catalase活性上升。此外，液態肥料中高濃度的氯化鈉，會造成蝴蝶蘭總葉綠素的含量下降。 綜合上述，高鹽度液態肥料致使介質鹽度增加造成鹽類逆境，使蝴蝶蘭生長量下降。蝴蝶蘭在不同生育階段對鹽度敏感度不同，小苗對液態肥料EC值的反應最為敏感，中苗次之、大苗之耐受性較高。高鹽度之液態肥料，將限制蝴蝶蘭對鉀離子、鈣離子及鎂離子的吸收。鹽類逆境下，蝴蝶蘭抗氧化酵素APX及Catalase活性上升，以降低氧化逆境之傷害。

The moth orchid (Phalaenopsis spp.) has different nutritional requirements at different growth stages, and hence may be subjected to different salinity levels under the same cultivation practices. A few work has been done to investigate the suitable salinity for growth and development of Phalaenopsis plants. However, how the plants respond to salinity is likely to be different during the various growth stages. In addition, how the different chemical composition of fertilizers affects Phalaenopsis plants subjected to similar salinity is still largely unknown. Inappropriate salinity levels may also cause oxidative stress in Phalaenopsis and the plants may thus activate antioxidant enzymes in order to reduce damage to the plants. This study aims to explore how the plants respond to salinity during various growth stages, and how antioxidant enzymes are activated to minimize plant damage, when phalaenopsis plants are under oxidative stress caused by inppropriate salinity. Phalaenopsis Sogo Yukidian ’V3’ was used in this study. Plants grown in 6-cm pots, 8.5-cm pots, and 10.5-cm pots were treated with fertilizer solution with different salinities. Medium salinity increased as fertilizer solution salinity increased. Under salinity stress, the growth and spiking percentage of Phalaenopsis plants are adversely affected. Phalaenopsis plants in different growth stages have different tolerance levels to fertilizer solution salinity. The fertilizer solution salinity for 6-cm pots should be lower than 1.15 dS•m-1 whereas for 8.5-cm pots it should be lower than 2.15 dS•m-1. The fertilizer solution salinity for Phalaenopsis plants grown in 10.5-cm pots should be lower than 3.15 dS•m-1. However, solution salinity should be lower than 2.15 dS•m-1 for acceptable spiking rate. Phalaenopsis plants were fertilized with fertilizer solutions having different ionic composition and salinity. Antagonism between ions was more pronounced with increased fertilizer solution salinity. Fertigation with salinity higher than 2.15 dS•m-1 reduced the absorbtion of potassium, calcium, and magnesium by Phalaenopsis plants. Under similar EC values, raising the concentration of sodium in fertilizer solutions. intensified the antagonism between ions, making it more difficult for the plants to absorb potassium, calcium, and magnesium. Phalaenopsis plantlets were cultured in 1/2 MS medium with different concentrations of sodium chloride added. The plantlets were able to grow and produce roots while the culture medium salinity ranged from 3.1 dS•m-1 to 5.5 dS•m-1. The addition of 0.1 g•L-1 sodium chloride to the culture medium promoted the growth of the plantlets and increased their total fresh weight and total dry weight. Phalaenopsis plants were fertilized with fertilizer solutions having different fertilizer and sodium chloride concentrations. The increase in medium salinity caused oxidative stress in Phalaenopsis plants. Hydrogen peroxide concentration, APX activity, and catalase activity in roots increased as medium salinity increased. Raising sodium concentration in fertilizer solutions will cause even greater oxidative stress. The chlorophyll concentration of Phalaenopsis leaves was affected by sodium concentration in the fertilizer solution. In summary, application of high salinity fertilizer solutions will increase the substrate salinity, cause salinity stress, and decrease the growth of Phalaenopsis plants. The sensitivity to salinity is different during the various growth stages of Phalaenopsis. Young Phalaenopsis plants potted in 6-cm pots are most sensitive to salinity, followed by medium-sized plants in 8.5-cm pots, then large plants in 10.5-cm pots. High-salinity fertilizer solutions inhibit the absorption of potassium, calcium, and magnesium in Phalaenopsis. Under salinity stress, increased activity is observed in antioxidant enzymes such as ascorbate peroxidase and catalase.