Red pitaya (Hylocereus sp.), which flowers between May and October and sprouts between November and May in Taiwan, has been confirmed to be a long-day plant. The areoles on the old shoots may be induced to flower after the March equinox naturally, and the floral bud formation occurs in two to three waves from May to October. We conducted experiments on photoperiodic regulation of floral bud formation from June to Dec. 2009 and tested the feasibility of off-season production in 2011. Shortening summer daylength to 8 h inhibited the areoles at the distal end of the shoots to develop into floral buds and promoted sprouting at the proximal ends of the shoots. Night-breaking treatment between the September equinox and the winter solstice led to floral bud formation. The critical daylength seemed to be ≈12 h, and night-breaking treatment would be applicable between the September and the next March equinoxes to produce off-season crops. The duration of night-breaking required for flower differentiation was longer in the cooler than in the warmer season. Four weeks of night-breaking treatment was sufficient to promote flowering in late fall (mid-October to mid-November), but 3 months were required to generate similar result in the winter and early spring (January to March) in southern Taiwan.

The effects of bagging on fruit characteristics and its role in physical fruit protection were investigated in three pitaya cultivars: Vietnam White (VN-White) and Chuchi Liu (Hylocereus undatus), and Chaozou 5 (Hylocereus sp.). The experiment comprised four treatments: paper-white bag (P-WB), net screen-black bag, polyethylene plasticblack bag (PP-BB), polyethylene plastic-white bag (PP-WB) and non-bagged control. Fruit bagging did not change the fruit lightness but significantly affected other peel colorimetric parameters. VN-White fruits bagged with P-WB became redder (a* ¼ 27.6), less yellow (b* ¼ 4.4) and had higher colour purity (h8 ¼ 10.7) than non-bagged fruits. Fruits with P-WB in Chuchi Liu also showed significant difference in b* and h8 values as compared with control. Bagging with PP-BB or PP-WB in Chaozou 5 also produced redder fruits (a* ¼ 31.7 and 30.3) with more colour intensity (C* 5 32.4 and 31.3) than non-bagged fruits. There were no significant differences in fruit size and weight, total soluble solids content and fruit ripening duration among treatments in all three cultivars. Fruit firmness also exhibited no significant differences among most treatments except for PP-BB, which gave a lower value than other treatments. In general, fruit bagging could reduce the peel thickness but could not increase the edible fruit rate. The most important role of fruit bagging was to effectively protect fruits from physiological factors such as cracking, bird damage and blemish, which led to the significant decrease of the total damaged and defective fruits (13.7-33.3%), as compared with non-bagged control (66.7-72.6%).

Yellow pitaya, Selenicereus megalanthus (Schum. ex. Vaupel) Moran, is a potential new fruit in Taiwan. It sprouts mostly in winter and flowers in late spring and fall. In this study, an average of 60% shoots within canopies flowered. Shoots sprouted in the current winter flowered in fall and produced winter fruits, and shoots sprouted earlier than the current winter flowered in late spring and produced summer fruits. Floral buds on most shoots appeared at the distal end. The weight, pulp percentage, and total soluble solids of winter fruits were significantly higher than those of summer fruits. The number of black seeds was positively correlated with pulp weight (R2 = 0.87). The total soluble solids in the core region of winter fruits reached 22.7 °Brix, higher than that in other regions. Future efforts to improve yellow pitaya production in Taiwan include increasing winter fruit production by enhancing growth of the current year's new shoots through proper canopy management and increasing the size of summer fruit by artificial pollination, fruit thinning, and other means.

Distribution of radiolabeled assimilates was examined at various intervals after 1 hour of light or dark 14CO2 fixation by leaves or developing fruit of grapefruit (Citrus paradisi Macf.) so that the fate of assimilates from each source could be assessed at sequential stages of fruit growth. Exported products of both light and dark 14CO2 fixation in leaves were deposited primarily in juice tissues of fruit even during periods of substantial dry weight accumulation by peel. Fruit photosynthesis, however, gave rise to assimilates that remained almost entirely in the peel (flavedo and albedo) even 7 days later, regardless of dry matter increases by other tissues. Products of dark 14CO2 fixation by intact fruit were recovered in all tissues but predominated in the peel of young fruit vs. juice tissues at later stages of growth. Comparison of dry matter gains and 14C-labeled assimilate distribution indicated that fruit photosynthesis likely contributed substantially to development of peel but not juice sacs. Data on dark 14CO2 fixation were consistent with its suggested involvement in organic acid synthesis by juice sacs.

Papaya (Carica papaya L.) is an important fruit crop in many tropical and subtropical countries; it is commercially propagated through seeds, which lead to production of non true-to-type plants. Grafting for mass multiplication of the selected variety is therefore necessary. The objective of this study was to determine the influence of rootstock age and grafting season on the success of cleft grafting and growth of grafted plants under greenhouse conditions. The trial was conducted using an experimental randomized complete block design with 4A × 2B factorial scheme, four blocks, and 15 grafted plants per experimental unit. Factor A represented four rootstock ages (1, 2, 3, and 6 mo) and factor B represented two grafting seasons (summer and autumn). Results showed that rootstock age and grafting season had a significant effect on all the parameters: sprouting time, percentage of graft success, scion sprout length, and number of new leaves per graft. The youngest rootstock age (1 mo) achieved the best results for all the parameters. The best season for grafting was summer. The treatment combination of 1-mo-old rootstocks in summer produced minimum sprouting time (8.40 d), the highest percentage of graft success (93.33%), and graft growth in the greenhouse. Therefore, 1-mo-old rootstocks and grafting in summer or autumn should be used to propagate papaya by cleft grafting.