生長季修剪對低海拔‘新興’梨(Pyrus pyrifolia Nakai.) 枝條生長、花芽形成及休眠之影響

Abstract

摘要 臺灣寄接梨所使用之溫帶梨品種逐漸多元，目前至少已有5種品種。本研究共 分為三部分。第一部分調查與檢定目前進口之主要梨穗品種，此外尚有高海拔所生產之國產溫帶梨。第二部分檢討夏季修剪對低海拔梨園中，當年高接‘新興’梨所長出枝梢之生長與花芽分化狀況。第三部分以正向逐步迴歸分析影響花芽比例之因子。第一部分試驗收集4種寄接梨之進口或國產品種，以及2種生產於臺灣高海拔山區，一般認為可能有潛力之溫帶梨品種。調查其外觀性狀，以芽角度、皮孔及芽形狀，可有效區分這六個品種。同時亦檢查其花芽分化狀況，但由於調查之枝條已事先選別過，花芽比例差異不顯著。第二部分之試驗於新埔地區‘新興’梨園進行，探討生長季修剪對‘新興’梨枝條生長，花芽發育與休眠性之影響，並於採收後以冷藏處理探究修剪處理對芽體生理休眠之影響。試驗結果顯示， 4月修剪者具有最佳之枝條長度、枝條直徑及節間長，5月以後修剪之枝條生長明顯受限。所有枝條均於7月達生長停滯、枝條長度不再增加。修剪次數對枝條生長量無顯著影響，推測可能原因為枝條提早成熟並停止，故無法顯現。修剪後之側芽萌芽率隨修剪時機越晚而有下降之趨勢，推測5月以後修剪之枝條除了受環境溫度所影響，亦受到枝條本身抑制物質所限制。對照組芽體於7月可肉眼觀察到花芽形成，由於具較長之生長季高溫期，其芽體壞死率最為嚴重。生長季修剪會改善花芽褐化率，亦同時增加健康花芽率。各修剪處理之花芽褐化情形皆有改善，以4月修剪有最佳之花芽形成率，且花芽壞死率降低幅度最大。5月以後修剪，花芽形成率較低，可能因為生長季時間較短花芽發育時間不足所致。未來可調整採收時間以改善花芽比例。枝條內容物分析結果顯示，巨量元素中除鉀以外，各修剪處理間無顯著差異。枝條採收後，以單芽插方式探討冷藏處理時間對各修剪處理之芽體萌發率之影響。結果顯示，冷藏1星期及冷藏2星期處理之枝條芽體萌發不一致，可能為低溫需求量不足所致。冷藏3星期之芽體均有萌發情況，以冷藏 4星期為最佳冷藏處理。其中以5月修剪及4+5月修剪之單芽插萌發率為最佳，均達50%以上。單芽插萌發率受冷藏時間所影響，冷藏時間越長，單芽插萌芽率具逐漸增加之趨勢。未來可針對冷藏時間做調整，以改善冷藏後枝條萌發情形。第三部分是探究各因子對枝條花芽比例之貢獻度，並建立相關預測方程式，以供未來枝條營養元素與花芽分化相關之研究做參考。巨量元素中以鉀含量與花芽比例關係密切，但因果關係仍需進一步闡明。生長季修剪可縮短枝條生長季之高溫期，進而改善芽體壞死之問題，使低海拔地區可進行梨穗之生產，本研究可作為未來低海拔地區生產梨穗之依據。

Abstract Cultivars of pear are gradually diversified, at least five cultivar of oriental pear are currently available in top-grafting pear industry. This study was divided into three parts. The first part was to verify the currently-main-import pear cultivars, and pears which was produced at high altitudes area. The second part was to study the effects of growing-season-pruning on shoots growth and flower differentiation of ‘Shinko’ pear in lowland area. In the third part, the factors affecting the percentage of flower buds were analyzed by forward stepwise analysis. In the first part, 4 kinds of pear cultivars were collected from foreign contries and domestic varieties.2 kinds of cultivars were collected from high altitude area in Taiwan which had more potential in Top-grafting pear industry. Bud characteristics such as bud angle, lenticels and shape of bud were used to distinguish the 6 cultivars and establish identify key of pear cultivars. Result of flower bud differentiation status observation showed that the percentage of flower buds was not significant different between cultivars. It may cause from that the pear scions had been previously selected. The second part was conducted in Xinpu township for summer pruning to investigate the effects of growing-season-pruning on shoots growth, flower bud development, dormancy of lateral bud, and the impact of pruning on the endodormancy of buds after harvesting. The results showed that, shoots pruned in April had best shoot length, shoot diameter, and the length of internode. After May, the growing of shoots was significantly limited. All shoots had growth cessation in July. The frequency of pruning has no significant effect to shoots growth. It is presumed that the reason may be the shoot matures early then stops, so it cannot be expressed. After pruning, percentage of lateral bud burst decreased along with delay of pruning. It speculated that the growth of shoots were not only affected by the high temperature in environment, but also restricted by the inhibitory substances of the shoots itselves. Flower bud formation could be observed visually in July, and the percentage of bud necrosis was the most serious due to a longer growth period in relative high temperature. Growing-season-pruning would reduce the necrosis of buds and also improved the proportion of flower buds in shoots. The flower bud drop rate of each pruning treatment was reduced. Pruned in April had best flower bud formation, and decreased the most percentage of bud drop. Pruning after May, the percentage of flower bud formation was low, which might be due to short growing time. Thus, to improve the flower bud formation, harvest time should be adjusted. Macronutrient of shoots showed that there were no significant difference among the pruning treatments except for potassium content in shoots. After the pear scions were harvested, the effect of storage treatment on the percentage of bud break in each pruning treatment was investigated by single-bud-cutting. The results showed that, bud break were inconsistent between one-week storage treatment and two-week storage treatment, which might be due to chilling requirement insufficient. In three-week storage treatment, bud break was observed in all of the pruning treatment. And the best storage treatment was performed in storage treatment for 4 weeks. Among them, the percentage of bud break for shoots pruned in May and pruned in April+May was the most, and all above 50%. The percentage of bud break was affected by the storage time. The longer storage time the higher percentage of bud break. In the future, storage time can be adjust to improve the percentage of bud break. In the third part, forward stepwise analysis was used to explore the contribution of each factor to the percentage of flower buds, and the relevant prediction equation was established for the reference of future research on the relationship between shoot nutrient elements and flower bud differentiation. C/N ratio and carbohydrate were the main factors in the two prediction equations, but the C/N ratio is the calculated value, so the equation which without the factor of C/N ratio is recommended. The content of potassium is closely related to the proportion of flower buds, but the causality needs to further elucidation. In order to solve the problem of pear scions, it is necessary for Taiwan to produce pear scions. Growing-season-pruning can shorten the high temperature period of the growing season, and reduced the necrosis of buds, so that the production of pear scions can be carried out in low altitude areas. This study can be used as the basis for the production of pear scions in low altitude areas in the future.