regeneration from cotyledonary node explants of Abelmoschus esculentus . Table 2. Effect of different concentrations of plant growth regulators (PGRs) in combination with silver nitrate (AgNO 3 ) and Pluronic F-68 on shoot regeneration from cotyledonary node
Muhammad Irshad, Hafiz Muhammad Rizwan, Biswojit Debnath, Muhammad Anwar, Min Li, Shuang Liu, Bizhu He, and Dongliang Qiu
Margaret J. Makinde, Adenike O. Olufolahji, and Olanrewaju A. Denton
A total of 45 varieties of okra (Abelmoschus esculentus) were evaluated for earliness in fruiting and high fruit yield. In Nigeria selection in okra is for large, spiny fruit with high drawing ability. So far the variety (cultivar) NHAC 47-4 has been well-accepted by both the Nigerian farmers and consumers. It fruit within 42 days and draws and retains fresh color when boiled. These new cultivars, NHAC147 and NHAC 148, were found to fruit within 38 to 40 days and they are of comparable yield of up to 40 fruit per plants. They were found to be drought-tolerant and carry fruit of up to five of same age and size-high degree of uniformity. They are therefore being recommended because they have short stems and NHAC148 has fewer spines than NHAC47-4 AND NHAC 147.
Seedling emergence and growth of 39 genotypes of okra [Abelmoschus esculentus (L.) Moench] were studied at several temperatures. Seeds were evaluated in two separate studies. One was a 3-year early planting field evaluation where air temperatures ranged from -2 to 29C. The other was a study at controlled temperatures of 10/10, 14/10, 15/15, 20/10, and 20/20C day/night. Okra genotypes showed variation in seedling emergence in the field, but the results fluctuated over years. Seedlings emerged at all the controlled temperatures, although the percentage of emergence reached only 13% at 10/10C. All temperature regimes produced some degree of leaf chlorosis, the severity of which was greatest at the lower temperatures. Leaves of none of the okra seedlings of any of the genotypes grew at 10/10, 14/10, or 15/15C. Genotypic variation in emergence was observed with the controlled temperatures.
The effect of moisture content on the emergence and development of `Pinkeye Purple Hull' and MN 13 cowpea [Vigna unguiculata (L.) Walp.] and `Clemson Spineless' okra [Abelmoschus esculentus (L.) Moench] seeds was investigated in a 3-year field study. Moisture content, ranging from 8% to 52%, was obtained by combining seeds, vermiculite, and varying volumes of water in sealed polyethylene packets and incubating them at 22C for 3 days. High moisture promoted the emergence of MN 13, did not significantly affect that of `Pinkeye Purple Hull', and decreased that of `Clemson Spineless' seeds. Percent seed emergence 22 days after planting averaged 17 % for `Clemson Spineless' and 15% for `Pinkeye Purple Hull' seeds, but was 44% for MN 13. High moisture generally promoted early harvest of MN 13 and increased root dry weight but did not affect fresh-pod yield significantly.
Lurline Marsh, Rufus Jones, and Mark Ellersieck
Growth and fruiting pattern of okra (Abelmoschus esculentus L. Moench) cv. Clemson Spineless as affected by the growth regulators Alar (N -dimethylaminosuccinamic acid) and ethephon (2-chloroethyl phosphoric acid) were evaluated in field studies. Eight treatments consisting of Alar at 600, 1200, 2400, and 3600 μl·liter-1 and ethephon at 200, 400, 600, and 800 μl·liter-1 and water control were applied as foliar sprays at the three- to four-true-leaf stage. Both growth regulators depressed shoot growth and leaf production. Ethephon reduced shoot length. Total fruit yield was not significantly affected by the treatments. However, ethephon-treated plants tended to produce fewer fruits and lagged behind Alar-treated plants and the control plants in Fruit production during the early harvests.
Yaying Wu, Brian A. Kahn, Niels O. Maness, John B. Solie, Richard W. Whitney, and Kenneth E. Conway
Okra [Abelmoschus esculentus (L.) Moench] was grown at various highly dense (HD) plant populations for destructive harvest, and compared with control plants grown at spacings of 90 × 23 cm and harvested repeatedly by hand. Our objectives were to identify a HD plant arrangement and an optimum harvest timing to maximize marketable fruit yield per hectare with a single destructive harvest, and to evaluate the potential for regrowth of cut plants followed by one or more subsequent harvests. Within HD treatments, marketable fruit weight per hectare tended to increase as the plant population density increased. Spacings of 30 × 30 cm and wider were not dense enough for the destructive harvest system due to a low marketable yield potential. Wide spacings did favor regrowth of cut plants in two experiments, but total marketable yields were still highest with the highest plant populations tested. Delaying destructive harvest until many overmature fruit were present did not consistently affect marketable fruit yield, but always decreased the proportion (by weight) of marketable fruit to total harvested fruit. Overall, percentages of marketable yield obtained by destructive harvests of plots with HD plant populations were low relative to the cumulative marketable yield from control plots. The lack of concentrated fruit set in okra remains a limiting factor for destructive harvest. However, the labor-saving potential of this system should stimulate further research.
W.F. Whitehead and B.P. Singh
Two studies were conducted to assess the effects of leaf aging on gas exchange in okra [Abelmoschus esculentus (L.) Moench] leaves. Gas exchange was measured at 6- to 10-day intervals starting 15 days after leaf emergence (DFE) and continuing until senescence at 50 DFE. Rates of transpiration (E), stomatal conductance (gs) and CO2 exchange (CER) increased as leaves matured up to ≈25 DFE, about full leaf expansion. Transpiration rate, gs, and CER declined after 25 DFE and as leaves aged further. Internal leaf CO2 concentration (Ci) was higher in old than young leaves. This study suggests that the most efficient okra canopy would maximize exposure of 25-day-old leaves to sunlight.
Lawford Baxter and Luther Waters Jr.
Okra (Abelmoschus esculentus L. Moench) pods stored In a controlled atmosphere (CA) of 5% O2 and 10% CO2 at 11 ± 1C and in air at the same temperature (RA) were compared to determine the effects of the two storage environments on changes in sugars, organic acids, proteins and amino acids, and ascorbic acid contents within the tissue. Pods were sampled at 3-day intervals for 12 days. CA-stored pods generally had greater retention of sugars, soluble proteins, and amino acids than RA-stored pods. Citric, malic, and ascorbic acids contents of CA pods also declined more slowly than those of RA pods.
W.F. Whitehead and B.P. Singh
A 2-year field study was conducted to determine the effects of within-row spacing (WRS) on CO2 exchange rate (CER), leaf-area index (LAI), and yield of okra [Abelmoschus esculentus (L.) Moench]. Okra cultivar Clemson Spineless was seeded at WRS of 8, 16, 24, 32, 40, and 48 cm in a randomized complete-block design replicated three times. CER and LAI were measured five times at about biweekly intervals between first flowering and final harvest. Fruits were harvested three times weekly for 7 weeks. There was no year-to-year variation in CER or LAI. Plants at 8 cm WRS attained maximum CER by 56 days after planting (DAP), while all other spacings took longer. CER at all WRS declined after 85 DAP. In 8 and 16 cm WRS, maximum LAI developed by 56 DAP, but 69 DAP were required at all other spacing. Depending on the spacing, LAI regressed linearly or cubically on DAP. Fruit number/plant (FNP), fruit fresh and dry weight/plant (FFW and FDW), and fresh and dry fruit yield/ha (FFY and DFY) were greater in 1991 than in 1990 as a result of more favorable weather during 1991. There was a linear increase in FNP, FFW, and FDW as WRS increased. Conversely, FFY and DFY were highest at 8 cm and decreased linearly in 1990 and quadratically in 1991 as WRS increased. Results of this study suggest that okra plants reach maximum CER and LAI earlier and produce higher fruit yield per unit area when spaced close together in the row.
Eric Simonne, Bob Hochmuth, Jeff Simons, Edgar Vinson III, and Arnold Caylor
Several okra (Abelmoschus esculentus) cultivars are now available as alternatives to the standards `Clemson Spineless' (open pollinated) and `Annie Oakley II' (hybrid). Based on the results of four trials involving 20 cultivars, `Mita', `Spike', `Green Best' and `North & South' should be added to the list of recommended cultivars for Alabama and Florida. The experimental `SOK 601' should also be included on that list, but on a for trial basis since it was evaluated only at one location. Other cultivars may perform well at specific locations. Differences among cultivars were also found for ease of harvest. `North & South' and `Baby Bubba' were the easiest and most difficult cultivars to harvest, respectively. The economic feasability of selecting a hybrid cultivar over an open-pollinated one and using plasticulture instead of bare ground was also examined in this study. Using hybrid seeds resulted in an average yield increase per harvest of 92 lb/acre (103 kg·ha-1), which exceeded the estimated 75 lb/acre yield (84 kg·ha-1) increase necessary to offset the additional cost of hybrid seeds. For reasons ranging from improved weed control, increased nutrient and water use efficiency, and double cropping, an increasing interest exists to produce okra with plasticulture, instead of bare ground as done traditionally. The average yield increase per harvest due to plasticulture over bare ground production was 196 lb/acre (220 kg·ha-1). Based on this number, it would take three harvests to produce the 540 lb/acre (605 kg·ha-1) yield increase necessary to offset the additional costs due to plasticulture.