溫度與光週期對‘桃園三號’草苺花芽形成之影響

Abstract

臺灣主要栽培草苺品種為‘桃園一號’和‘桃園三號’。‘桃園一號’(‘豐香’)是日本引進之品種，已累積相當多的研究資料，但針對臺灣育成之‘桃園三號’草苺的開花研究則相當少。因此本試驗藉由溫度對光週期之組合，歸納適宜及抑制‘桃園三號’草苺開花之環境條件，希望藉此檢討現今的栽培曆，以期達到有經濟效益的產期調節方法。 溫度試驗中，‘桃園三號’草苺在13.5小時的日長下，配合25/20℃，即能產生花芽並抽出，符合超短日型(ISD)草苺之條件，日長與涼溫需求不甚嚴苛。25/20℃處理者可於生長箱處理期間始花，早於20/15℃、15/10℃處理者。顯示，植株營養生長狀態，與花序抽出的能力相關。20/15℃、15/10℃處理者，植株逐漸進入休眠，葉面積變小、葉柄變短，植株呈簇生狀，根系雖然在涼溫生長相對旺盛，但地上部植株生長活力大幅下降，且15/10℃處理者葉片數顯著較少，因此花序遲遲無法抽出。2009年的試驗，處理後的田間表現，由整體累積花序數量觀之，20/15℃、15/10℃處理者的花序數量，最後仍不及25/20℃處理，尤其15/10℃處理者的表現，比戶外對照組還差。因此，未必是溫度越低，促進花芽分化的效果越好。 增加光照的各項處理，無論是延長日長，或是利用暗中斷的方法，均可促使已形成花序抽出且齊一、走莖萌發、葉柄增長、葉面積增加等。田間以白熾鎢絲燈為主的暗中斷處理，可有效抑制植株後續花芽分化，植株可於暗中斷處理後的2個月左右抽出花序。但生長箱中以日光燈進行暗中斷處理，則未能達到抑制花芽的效果，因此必須考量燈具的類型，所提供的光源波長、照度、頻度等細節條件，以及處理的時間點，與處理時間長度等。日長處理部份，20/15℃下，16小時之日長，無法完全阻止花芽形成，顯示臨界短日會隨溫度而改變。 綜合溫度與光週期試驗結果，藉由增加光照的方式，可提早育苗時間、提昇苗的品質。再給予低溫短日 (20/15℃，短於13.5小時即可) 處理，便可提早草苺產期。若要延後產期，可仰賴低溫處理迫使植株休眠，或是光照抑制的方式進行，依照實際情況，考量處理成本進行搭配，未來臺灣的草苺產期，絕對不僅僅侷限於11月至4月之間。

Fragaria ×ananassa Duch. cv. ‘Taoyuan No. 1’and F. ×ananassa Duch. cv. ‘Taoyuan No. 3’are the main strawberry cultivar planted in Taiwan. ‘Taoyuan No. 1’ (‘Toyonoka’) was introduced from Japan, which had been accumulated a lot of studies. However, as the first cultivar that had been bred in Taiwan, there is not much information about flowering of ‘Taoyuan No. 3’. Therefore, by treating different temperature and photoperiod combinations, this study aims to figure out suitable and unsuitable conditions on floral bud formation of ‘Taoyuan No. 3’. We want to review current cultivation pattern, and discuss economical ways to adjust the harvest. In the temperature experiments, ‘Taoyuan No. 3 was able to form and sprout floral bud under 13.5-hour-daylength with 25/20℃. This behavior is meet to the term of infra short-day strawberry. Excessively strict daylength and cool temperature are not necessary for floral bud formation. 25/20℃ treatment sprouts the inflorescences in growth chamber earlier than 20/15℃ and 15/10℃. It shows that vegetative growth state affects the ability to sprout inflorescences. Since the plants gradually went into dormancy under 20/15℃ and 15/10℃, with smaller leaf area, shorter petiole, and clustered appearance. Although root growth was relatively better in the cooler temperature, but shoot growth activity was greatly reduced, especially 15/10℃ treatment had significantly less number of leaves, leading to postpone the sprouting of inflorescences. After the treatment, eventually the total inflorescence number of 20/15℃ and 15/10℃ were not as much as 25/20℃. Even the total inflorescence number of 15/10℃ was less than the outdoor control. Therefore, it is not lower the temperature, the better to promote flower bud formation. The treatment of increase the illumination, whether to prolong the daylength, or use night break methods, was able to promote the existing inflorescence sprout uniformly, as well as the germination of runners, the prolongation of petiole, and the extension of leaf area. Using incandescent filaments as major light source of night break, it was able to inhibit the later floral bud differentiation efficiently in the field. After the night break, plants could sprout the inflorescences about 2 months later. Thus we must consider the form of light source that involving the details about wavelength, light intensity, frequency etc., and treat processing timing with an appropriate length. In addition, the treatment of daylength, the floral bud formation could not be suppressed completely under 20/15℃ with the 16-hour-daylength. It indicates the critical short day of ‘Taoyuan No. 3’ will change with temperature. Integrating the results of temperature and photoperiod treatments, we can propagate strawberry runner plants earlier by increasing light. The earlier we propagate the easier to improve the quality of runner plants. And then we could harvest strawberries earlier by low temperature and short day treatments (about 20/15℃, less than 13.5-hour was recommended). Also, the strawberries could be forced go into dormancy by low temperature, or inhibited the floral buds by increasing light. Considering the actual situation with the cost, it would be advantageous to delay the harvest by these ways. In the future, the harvest season of strawberry would not be definitely limited form November to April in Taiwan.