Water relations and fruit development were studied for up to 100 days after anthesis for potted plants of Opuntia ficus-indica (L.) Mill. (a prickly pear) that were either well-watered or water-stressed, each plant consisting of a medium-sized cladode bearing two or three fruit. Even though cladodes of water-stressed plants lost up to 50% of their thickness, their fruit continued to gain water and to develop; at ripening such fruit had only 16% less water than fruit of watered plants. Maturation indicated by the decrease in fractional peel content and increases in pulp weight and in pulp soluble sugar content was hastened by water stress, leading to ripening ≈88 days after anthesis for water-stressed plants, which was 10 days earlier than for watered plants. Fruit had a lower stomatal frequency than the cladodes but both exhibited Crassulacean acid metabolism behavior. Transpiration occurred mainly at night, and the daily amount of water transpired per unit fruit surface area decreased with time, especially for fruit of water-stressed plants. This decrease was related to fruit expansion (leading to decreased stomatal frequency) for watered plants and to both fruit expansion and water stress for water-stressed plants. At 75 days after anthesis, daily diameter changes of fruit were correlated with transpiration, contraction occurring at night and expansion during the daytime, and changes were greater for watered plants for which daily transpiration was higher.
Avinoam Nerd and Park S. Nobel
Victor Garcia de Cortázar and Park S. Nobel
Productivity of irrigated prickly pear cactus [Opuntia ficus-indica (L.) Miller] was studied over 3 years in central Chile using two planting densities. A low-density planting (0.25 plants/m2), traditionally favored for fruit production, had maximal fruit productivity in the 2nd year (6 Mg dry weight/ha per year). A high-density planting (24 plants/m2), which assured almost full interception of incident solar radiation, led to an extremely high shoot dry-weight productivity (50 Mg·ha-1·year-1) in the 2nd year and maximal fruit productivity (6 Mg·ha-1·year-1) in the 3rd year. Cladode dry weight tended to increase with cladode surface area. However, fruit production did not occur until the dry weight per cladode exceeded the minimum dry weight for a particular cladode surface area by at least 33 g. The year-to-year variation in fruit production apparently reflected variations in such excess dry weight and, hence, in the storage reserves of individual cladodes.
Park S. Nobel and Miguel Castañeda
Detached, unrooted cladodes (stem segments) of the widely cultivated prickly pear cactus Opuntia ficus-indica (L.) Miller (Cactaceae), which remain alive for at least 12 months, provide a model system for investigating stem responses to environmental factors. Initiation of organs varied seasonally; on average 2.14 new organs were initiated per cladode over a 16-week period in a glasshouse for cladodes detached in winter, 0.76 when detached in late spring, and only 0.07 when detached in late summer. Shading by 45% halved new organ initiation and shading by 95% decreased it by 96%. The seasonal and light responses for new organ initiation are consistent with field observations on O. ficus-indica. For detached cladodes maintained in environmental chambers for 14 weeks, the new organs were 10 times more likely to be fruit than daughter cladodes at day/night temperatures of 15/5 °C, equally likely to be either organ at 25/15 °C, and 10 times more likely to be daughter cladodes than fruit at 35/25 °C. Decreasing the shading or the temperature favored stomatal opening, as shown by increases in the dry mass/fresh mass ratio of the detached cladodes. Such increased stomatal opening was accompanied by increased photosynthetic activity, as shown by greater starch content and higher concentrations of sucrose, glucose, and fructose. Why low day/night temperatures favored reproductive structures and high temperatures favored vegetative ones is not clear, but future research using unrooted cladodes may help elucidate the mechanisms involved.
P. Inglese, G. Barbera, T. La Mantia, and S. Portolano
We established a cladode load and thinning time that maximized fruit and flesh size in `Gialla' cactus pear (Opuntia ficus-indica Mill.). Five weeks after spring flush removal, second flush flower buds were thinned to nine, six, or three per cladode; the same treatment was repeated during the early stages of fruit development. Control cladodes had a natural load of 15 fruit. Time of thinning did not affect fruit growth and ultimate weight. Fruit and flesh weight increased with thinning, but export weight was obtained only in cladodes with no more than six fruit. Heavier thinning did not result in any further increase of fruit or flesh weight. Percent flesh was not affected by thinning. Fruit characteristics, such as total soluble solids concentration and seed content did not change with thinning, but the seeds: flesh ratio decreased with thinning. Fruit on cladodes with the lowest load ripened earlier than those on more heavily yielding cladodes.
Avinoam Nerd, Avraham Karady, and Yosef Mizrahi
Field experiments were conducted to examine the effect of fertilization and short periods of drought on the out-of-season winter crop in prickly pear [Opuntia ficus-indica (L.) Mill.]. In addition, the winter and summer crops were compared regarding floral bud production and fruit characteristics. Under both continuous fertigation (N, P, K applied with the irrigation water) and continuous irrigation, the number of floral buds per plant was much lower in the winter than in the summer crop. Fertilization increased production of floral buds in both crops, but to a greater extent in the winter crop. The increase in floral bud production in fertilized plants was associated with an increase in NO3-N content in the cladodes. Suspension of fertigation for 4 or 8 weeks immediately after the summer harvest decreased cladode water content and delayed and reduced floral bud emergence as compared with continuous fertigation (control) or late drought (4 or 8 weeks) applied 4 weeks after the summer harvest. The plants subjected to early drought suffered from high mortality of floral buds. The fruits of the winter crop ripened in early spring, following the pattern of floral bud emergence the previous autumn. Mean fresh weight and peel: pulp ratio (w/w) were higher in fruits that ripened in the spring (winter crop) than in fruits that ripened in the summer.
P. Inglese, G. Barbera, and T. La Mantia
Flowers and stems (cladodes) of cactus pear [Opuntia ficus-indica (L.) Mill.] appear simultaneously in spring, and a second vegetative and reproductive flush can be obtained in early summer by completely removing flowers and cladodes of the spring flush at bloom time. The seasonal growth patterns of cactus pear fruits and cladodes were examined in terms of dry-weight accumulation and cladode extension (surface area) to determine if cladodes are competitive sinks during fruit development. Thermal time was calculated in terms of growing degree hours (GDH) accumulated from bud burst until fruit harvest. Fruits of the spring flush had a 25% lower dry weight and a shorter development period than the summer flush fruits, and, particularly, a shorter duration and a lower growth rate at the stage when most of the core development occurred. The duration of the fruit development period was better explained in terms of thermal rather than chronological time. The number of days required to reach commercial harvest maturity changed with the time of bud burst, but the thermal time (40 × 103 GDH) did not. Newly developing cladodes may become competitive sinks for resource allocation during most of fruit growth, as indicated by the cladode's higher absolute growth rate, and the fruit had the highest growth rate during the final swell of the core, corresponding to a consistent reduction in cladode growth rate. Cladode surface area extension in the first flush ceased at the time of summer fruit harvest (20 Aug.), while cladodes continued to increase in dry weight and thickness until the end of the growing season (November), and, eventually, during winter. The growth of fruit and cladodes of the summer flush occurred simultaneously over the course of the season; the cladodes had a similar surface area and a lower (25%) dry-weight accumulation and thickness than did first flush cladodes. The proportion of annual aboveground dry matter allocated to the fruits was 35% for the spring flush and 46% for the summer flush, being similar to harvest increment values reported for other fruit crops, such as peach [Prunus persica (L.) Batsch.]. Summer cladode pruning and fruit thinning should be accomplished early in the season to avoid resource-limited growth conditions that could reduce fruit and cladode growth potential.
Jorge A. Zegbe and Jaime Mena-Covarrubias
thinning and irrigation on determining fruit quality of cactus pear ( Opuntia ficus-indica ) fruits Acta Hort. 581 205 209 Inglese, P. 1995 Orchard planting and management 78 91 Barbera G. Inglese P. Pimienta-Barrios E. Agro-ecology, cultivation, and uses
Neil O. Anderson and Richard T. Olsen
Rosa, CA Griffith, M.P. 2004 The origins of an important cactus crop, Opuntia ficus-indica (Cactaceae): New molecular evidence Amer. J. Bot. 91 1915 1921 Griffiths, D. 1905 The prickly pear and other cacti as food for stock. USDA Bur. Plant Ind. Bul
Flavonoid content and antioxidant activity in peel and pulp samples of four different cactus pear fruit varieties were investigated. Major cactus fruit flavonoids were quercetin, kaempferol, and isorhamnetin. Greater amount of quercetin was found in the pulp compared with the peel samples in all varieties examined. Both kaempferol and isorhamnetin were found in at least three of the varieties (Opuntia ficus-indica; O. lindheimeri; O. streptacantha) exclusively in the peel samples. Generally, pulp tissue samples of all the cactus fruit varieties contained greater ascorbic acid, glutathione, alpha-tocopherol and beta-carotene and antioxidant activities than the peel tissue samples. Total flavonoids correlated well with antioxidant activity (r 2 = 0.89). Ascorbic acid had the highest antioxidant activity, followed by glutathione, beta-carotene, and alpha-tocopherol on equimolar basis.
M. Schirra, M. Agabbio, S. D'Aquino, and T.G. McCollum
The influence of postharvest heat conditioning at 38 °C for 24, 48, or 72 hours on ripe `Gialla' cactus pear [Opuntia ficus-indica (L.) Miller] fruit produced by the spring flush was investigated during 21 days of storage at 6 °C and 90%-95% relative humidity (RH) followed by 7 days at 20 °C and 70%-75% RH (simulated marketing). Conditioning for 24 to 72 h reduced by 50% the severity of chilling injury (CI) on cactus pears following exposure to cold storage. Treatment for 24 to 72 h was also effective in reducing decay, with conditioning for 24 h being the most effective. Overall visual quality was better in heat-conditioned compared with control fruit. Mass loss was significantly reduced by all heat conditioning treatments. Respiration rate was not affected by heat treatment. Ethylene evolution was lower in fruit heat-conditioned for 48 or 72 h than for 0 h. Conditioning for 72 h resulted in the highest fruit ethanol levels. The influence of conditioning on juice pH, titratable acidity, soluble solids concentration and ascorbic acid was negligible. Prestorage heat treatment provides some measure of CI and decay control without detrimental effects to visual quality of early ripening cactus pear fruit and may offer an alternative to fungicide treatments.