Lability of Floral Organization in Hermapfrodite Papaya( Carica papaya L.)

• Main Authors: Wen- Chin Wang, 王聞淨
• Other Authors: Loong-Sheng Chang
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/49093119519170314878

碩士 === 國立臺灣大學 === 園藝學研究所 === 88 === Ⅰ.Hermaphroditic plant is predominately cultivated for papaya production, and its unstable floral expression has caused yield reduction. Genetic, temperature and physiological factors are known to correlated with floral expression of papaya. However, the leading physiological factor remain unknown. In this study we investigate floral sex variation of hermaphrodite papaya c.v. ''TN-2'', ''TN-6'', and ''Thailand'' and conduct four defloration treatment:(1).control, (2).removal of terminal flower of axis, (3)remaining of terminal flower of 2nd peduncle, and (4).remaining of terminal flower of axis, different inflorescence positions within tree( young bud, before anthesis, and anthesis section). ‘TN-6’ exhibit most stable floral type expression, and highest percentage of elongata flower (78.31%) among three cultivars. The most labile cultivar is ‘Thailand’ while it express highest percentage of abnormal floral types and lowest percentage elongata flower( 38.1%). Inflorescence positions within tree effect floral type expression. Percentage of elongata flower is 64.18%, 62.07%, and 39.41% in inflorescence of young bud, before anthesis and anthesis section, respectively. Percentage of both pistilloid flowers is the lowest, but the highest in inflorescence of young bud and on anthesis section, contrary. Floral type expression variation among sections may result from differential developmental stages among sections when deflorated or from differential environmental factors among sections during floral development. There was floral type expression variation also exist within inflorescence. Percentages of elongata flower on terminal flower of axis is 55.17%, which is significantly higher than that on terminal flower of 2nd peduncle(43.02%). Percentage of mild carpelloid flower on terminal flower of axis is 28.74, which is significantly higher than that on terminal flower of 1st and 2nd peduncle(10.47% and 3.49%, respectively). Percentage of both pistilloid flower on terminal flower of 2nd peduncle are 11.63% and 15.17%, respectively, which is significantly higher than that on terminal flower of axis(3.45% and 1.15%). It indicate that terminal flowers tend to exhibit female like and terminal flower of 1st and 2nd peduncle tend to exhibit malelike. Since percentages of elongata flower increase, and pistilloid flower decrease on terminal flower of 2nd peduncle when older flowers are removed, it reveal that interorganic competition leads to inhibition of pistil organization of younger flower bud. Our data show that removal of both terminal flowers of axis lead decrease carpelloid flowers per inflorescence in anthesis section, but also decrease elongata flowers if all type of flower removed. It should be practical to decrease abnormal fruits by selected removal of abnormal flower on terminal flower of axis when anthesis . Our study suggests that floral sex variation in papaya is an important phenotypic plasticity which confer series temporal and spatial adjustment points in investment of reproductive growth when it response to flexible environments. Ⅱ.The floral sex expression of hermaphrodite papaya fluctuate environmentally. The instability reduced papaya fruit production. Two treatments were follow as: (1). net house shaded control and (2). 90% PAR shaded. Four defloration treatments such as: (1) control, (2) removal of terminal flower of axis, (3) remaining of terminal flower of 2nd peduncle, and (4) remaining of terminal flower of axis, were practiced to manipulate sink and source conditions. The percentages of elongata flower under 90% shaded（13.56% and 10.07% for ‘TN-2’ and ‘Thailand’, respectively）were significantly lower than these under the control net house treatment（41.5% and 34.6% for ‘TN-2’ and ‘Thailand’, respectively）. Shading decreased the percentages of carpelloid flower. But it increased the percentages of pistilloid flowers and abscission buds. Photosynthesis rate, stem diameter, and numbers of differentiated node weekly and survival leaf significantly decreased after 90% shading. Limitation of photosynthesis by reducing PAR under shading might cause papaya to surfer photosynthatic stress, to reallocate resource to male and female function, to disturb floral organization, and lead to changes of floral sex expression. Defloration treatments manipulated various sink status on treated nodes, and which those effects were more flowers and setting more fruit, to produce fewer elongata and carpelloid flower and more pistilloid flowers on organizing floral buds. It indicated that interorganic competition led to resource constraint, by which carpel organization inhibited. There were highest percentages of elongata and carpelloid flower, but the lowest percentages of abscission bud and pistilloid flower on the terminal flower of axis. The inflorescence labeled as 7th node at 1 week after shading was responsible to shading effect on floral sex expression, and shading effect disappear at 1 to 2 week after terminate of shading. Our study shew that resource deficiency, which might be caused both by source reduction and/or sink competition, inhibit carpel organization, to decrease number of elongata flowers, and to promote more pistilloid flower formation.