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Carl E. Motsenbocker

Pepperoncini pepper (Capsicum annuum var. annuum L. `Golden Greek') was grown at in-row spacings of 7.5, 15, 22.5, 30, and 45 cm to determine the effect of plant population on growth and fruit yield in a 2-year field study. In 1992, pepper plants grown at the 15-cm in-row spacing had the lowest plant, stem, and leaf dry weights, while plants at the lowest density (45-cm spacing) had the highest plant, leaf, and stem dry weights and the largest leaf area (LA). Of plants grown at the 7.5-cm spacing, the total yield and fruit count per hectare were higher than at the other spacings; however, fruit yield per plant was lowest. In 1993, the lowest plant and leaf dry weights and LA and highest LA index (LAI) were from plants at the 7.5-cm in-row spacing. Plants at the 45-cm spacing had the highest plant and leaf dry weight and LA and the lowest LAI. Pepper plants grown at the narrowest spacing produced the lowest early and total fruit yield per plant but the most fruit per hectare. In general, plants grown at the narrowest spacings produced the smallest plant, leaf, and stem biomass but resulted in the highest fruit yields and counts per hectare and the lowest fruit yields per plant.

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Carl E. Motsenbocker

Field and greenhouse studies examined the fruit detachment force (FDF) and fruit and pedicel characteristics of two lines of tabasco pepper (Capsicum frutescens L.) at several stages of maturity. The detachment force of red-mature `McIlhenny Select' fruit at the calyx-fruit detachment area was lower than that of less mature fruit stages. The force required to detach red-mature Hard Pick (HP) tabasco fruit was higher than that of redmature `McIlhenny Select' fruit in the field and greenhouse. The fruit detachment force of red field-grown HP fruit was higher, and in the greenhouse was lower, than that of green or breaker fruit. HP fruit of all maturity stages, except red-mature, separated similarly to `McIlhenny Select' fruit with little or no fruit tissue attached to the calyx. Fruit detachment force was not correlated with any fruit or pedicel characteristics studied.

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Koji Takeuchi and Carl E. Motsenbocker

Tomato is an important vegetable crop in Louisiana for small- to large-scale growers. Growers often use protected cultivation with structures, such as greenhouses, in order to take advantage of higher prices early in the season and increase profits through increased tomato yield and quality. A negative aspect of greenhouse use is the high investment and production costs associated with these structures. High tunnels, or simple greenhouse-like structures, have been used to protect crops from cold temperature in northern states, as they often provide benefits similar to greenhouses with considerably lower cost. Very little research has been conducted on the use of high tunnels for crops in the southern states. High tunnels in combination with row covers were evaluated for field cultivation of spring season fresh market tomato in Louisiana. The studies were set up in a randomized complete-block design with three replications. Tomatoes were transplanted into single rows on four-row raised beds covered with black plastic mulch on 1.2-m centers on 13 Mar. 2004. Row covers were installed immediately after transplanting and removed on 3 May. Plants were harvested for 6 weeks starting 12 May 2004. Both high tunnels and row covers significantly increased minimum and maximum air temperatures at a 15-cm height compared to the black plastic mulch control. Early yield was highest with the tunnel treatment without row cover compared to tunnel with row cover and similar to row cover alone or the control. There were no differences in total marketable yield between treatments. Research results from 2 years will be presented.

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Ramón A. Arancibia and Carl E. Motsenbocker

Pectin metabolism was analyzed in tabasco pepper (Capsicum frutescens L.) to determine the metabolic process associated with the ease of fruit detachment from the calyx. The ease of fruit detachment (deciduous fruit) is a desirable trait in peppers that facilitates mechanical harvest. Two genotypes that differ in the fruit detachment force were used: `Easy Pick' (EZ), which requires a low force, and `Hard Pick' (HP), which requires higher force. Pectin dissolution in water from fresh-ripe EZ tissue was 20 times higher than from HP tissue. EDTA-soluble uronide from inactivated EZ cell wall, however, was only 1.8 times higher. Pectin dissolution was inversely correlated to the fruit detachment force and followed a sigmoidal curve during fruit ripening. Size-exclusion chromatography of EDTA-soluble polyuronides indicated that pectin was degraded in ripe fruit tissue from both genotypes. The degree of depolymerization, however, was more extensive in EZ fruit. Consequently, the ease of fruit detachment was attributed to pectin ultra-degradation. Total pectin content in dry tissue and ethanol/acetone-extracted cell wall was similar in both genotypes. Pectin content in dry tissue was maintained throughout ripening, while extracted cell wall pectin increased slightly. In contrast, the degree of pectin esterification of extracted cell wall decreased only in ripe EZ fruit. These results suggest that pectin de-esterification may have a role in the enhanced pectin depolymerization and consequently in the ease of fruit detachment of the EZ genotype.

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Ramón A. Arancibia and Carl E. Motsenbocker

Plasticulture has been successfully used to enhance growth and yield of horticultural crops, and also for season extension in cooler climates. The effect of three plastic mulches (silver on black, photoselective thermal green, and black) in combination with spunbonded polyester rowcover (0.9 oz/yard2) on spring-planted watermelon (Citrullus lanatus) production was investigated. Two red-fleshed cultivars [Sangria (seeded) and Crimson Jewel (triploid)] were used. Plastic mulches increased early and total marketable yield in comparison with bare ground for both cultivars, but net benefit increased in ‘Crimson Jewel’ only. In contrast, yield and net benefit were the same among plastic mulches. Rowcover increased soil and air temperature, with the effect being greatest at lower ambient temperatures. During a near-freeze event, air temperature under the rowcover was about 7.2 °F higher than without a rowcover. Rowcover increased early and total marketable yield, but fruit weight decreased in both cultivars. Yield distribution into three fruit size categories was inconsistent between the cultivars. In ‘Sangria’, the large fruit category had the highest yield proportion for all treatments. In contrast, the highest yield proportion of ‘Crimson Jewel’, with exception of mulch without rowcover, corresponded to small fruit. Rowcover increased gross income at wholesale prices, but net benefit was not different from without rowcover. Protection of high-value plants, such as triploid watermelon, against light freezes, however, may still justify the use of rowcover in early plantings.

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Carl E. Motsenbocker and Ramon A. Arancibia

Triploid watermelon (Citrullus lanatus), commonly called seedless watermelon, is increasing in popularity and market share. The optimum in-row spacing of triploid watermelon has not been studied previously. Triploid watermelon `Crimson Jewel' and `Honeyheart' were grown with drip-irrigation and black plastic mulch at 1-, 2-, 4-, 6-, and 8-ft (0.3-, 0.6-, 1.2-, 1.8-, and 2.4-m) in-row spacings in 1996 and 2-, 3-, 4-, 5-, 6-, 7-, and 8-ft. (0.6-, 0.9-, 1.2-, 1.5-, 1.8-, 2.1-, and 2.4-m) spacings in 1997 to determine the effect of in-row plant spacing on fruit yield. Marketable yield of `Crimson Jewel' was not affected by in-row spacing while narrower in-row spacing resulted in greater `Honeyheart' yield both years. For both cultivars, narrower spacing resulted in the highest number of fruit per acre, but primarily more extrasmall and small fruit. Fruit number per plant, fruit weight per plant, and individual fruit weight were higher at wider spacings, and yield per acre was lower. The data suggest that triploid watermelon yield, fruit weight and number can be adjusted by in-row spacing. Narrower in-row spacing can maximize yields, depending on the specific grower's cultural practices. In wider in-row spacings, the yield of medium and large fruit is maintained with a subsequent decrease in extra small and small fruit. Gross returns per acre were only different for farmers' market prices, not wholesale, and net returns were not significantly influenced by in-row spacing.

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Leanna L. Smith and Carl E. Motsenbocker

The first four chapters of a hands-on gardening curriculum (Junior Master Gardener Handbook Level One) were introduced into three East Baton Rouge Parish (Louisiana) elementary schools in the fall semester of 2002 as an informal education program conducted by East Baton Rouge Parish Master Gardener volunteers and Louisiana State University students. The curriculum took place once per week for 2 hours during regular school hours. Science achievement tests, developed at Texas A&M University specifically for the Junior Master Gardener program, were given before and after the students participated in the gardening activities to determine whether or not the activities helped improve achievement scores. Science achievement was significantly different (P ≤ 0.0167) between the experimental classes' pretest and posttest scores, while no significant difference was found between the pretest and posttest scores of the control classes. No significant difference was found between the experimental and control classes due to treatment. Several variables may have affected the outcome of the study, but the results show once weekly use of gardening activities and hands-on classroom activities help improve science achievement test scores.

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Carl E. Motsenbocker and Kay P. Gersch

Field and greenhouse studies were conducted to examine fruit detachment force and plant parameters of two strains of Tabasco (Capsicum frutescens) at different stages of maturity. The detachment force of mature red `McIlhenny Select' at the fruit-receptacle detachment area was less than that of breaker and mature green fruit. `McIlhenny Select' separated cleanly at all stages of maturity. A wild type Tabasco strain `HP' did not abscise at the red mature stage; fruit detachment force was greater than that of `McIlhenny Select'. The detachment force of mature green and breaker `HP' fruit were similar to those of `McIlhenny Select' at the same stage of maturity. Fruit weight, length, and width of the two tabasco strains were not different. The utility of the `McIlhenny Select' and `HP' strains for physiological studies of pepper fruit abscission will be discussed.

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Ramon A. Arancibia and Carl E. Motsenbocker

`McIlhenny Select' (easy detachment) and `Hard Pick' are two lines of tabasco pepper (Capsicum frutescens L.) that differ in the fruit detachment characteristics. Cellulase (Cx) and polygalacturonase (PG) activity, extracted from the fruit abscission zone, correlated inversely with the force needed to separate the fruit from the pedicel. A trend of higher Cx and PG is associated with the lower detachment force in the McIlhenny Select line. Differences in the fruit cell wall protein profile between both lines occurred during ripening. Two bands of 23 kDa and 40 kDa were higher in `McIlhenny Select'. A band of approximately 30 kDa was higher in `Hard Pick', while a band of ≈70 kDa increased in both lines. Isolation and characterization of these bands as well as Cx and PG is needed to understand the factors affecting fruit detachment in tabasco pepper.

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Carl E. Motsenbocker and Ramon A. Arancibia

Two tabasco pepper (Capsicum frutescens L.) lines were previously identified that differ in fruit detachment characteristics. Ethephon treatment (1000 μl/L) to intact tabasco fruit 29 days after anthesis (green-mature) enhanced ripening as indicated by fruit coloration in both lines. `McIlhenny Select' fruit, which normally separate readily at the red-mature stage, however, had a quicker ripening response compared to `Hard Pick' fruit. Ethephon increased cellulase activity in the fruit tissue of both tabasco lines compared to the untreated control, and there was a trend of higher cellulase activity in `McIlhenny Select' compared to `Hard Pick'. Differences in ripening and enzyme activity in response to ethylene generators indicate that the two tabasco lines are suitable material to investigate the physiological processes involved in pepper fruit ripening.