Abscission Of Reproductive Structures Research Articles

English

At the application time of sugarcane ripeners, most times, morning glory plants, that have escaped, survived or emerged, are entwined on sugarcane stalks and these plants are at this time in different reproductive stages (and it becomes more difficult to control) causing a mechanical and crop yield damage. The main aim of this research was to evaluate sugarcane crop ripeners effect on the seeds germination, seedling development and the abscission of the reproductive structures of morning glory. The treatments consist of five ripeners: ethyl-trinexapac (300 ga.i.ha-1), glyphosate (216 ga.i.ha-1), fluazifop-p-butyl (75 ga.i.ha-1), sulfometuron-methyl (15 ga.i.ha-1), ethephon (480 ga.i.ha-1) and one control plot (without ripener application). They were applied during the reproductive stages of morning glory. The experimental design used was completely randomized design with four replications and six treatments, to a total of 24 plots. After ripeners application, abscised reproductive structures were counted to determine the percentage of abscission. The seeds of each phenological stage were collected when it reached the point of physiological maturity and it was set to germinate in Petri dishes to evaluate the germination rate, germination mean time, germination velocity, initial growth and dry mass weight. Trinexapac-ethyl, glyphosate and fluazifop-P-butyl application when plants are with open flowers can reduce seed viability. Glyphosate showed the smallest length value and it can affect seedling growth. Glyphosate and ethephon caused the highest percentages of abscission of morning glory reproductive structures and they can contribute to reduce the seeds inflow to the soils. Key words: Abscission, Ipomoea hederifolia, plant growth regulator, reproductive structure

Path models for the abscission of reproductive structures in three contrasting cultivars of faba bean (Vicia faba)

We hypothesized that the differences in the amount of abscission of reproductive structures in three physiological types of faba bean (Vicia faba L.) were due to different physiological responses to an internal competition for resources in the plant. Vicia faba 'Aguadulce' has an indeterminate growth habit and a dichotomous system of vascularization in its inflorescences. Vicia faba 'D83146-123' has a determinate growth habit and a dichotomous system of vascularization in its inflorescences. Vicia faba 'B 87.151' has an indeterminate growth habit and an independent vascular system in its inflorescences. Flower and pod abscission were related to growth and developmental attributes using multiple regressions as well as path analysis. The path models showed that abscission in the determinate growth cultivar was positively related to plant height and branch number, suggesting that competition for vegetative growth is still responsible for abscission in this cultivar. Future breeding should focus on reducing branch number in this cultivar. Results suggest that competition between reproductive structures has been attenuated in the independent vascular system cultivar even if flowers and pods continue to abscind. Further selection should be concentrated on a reduction of height and an independent vascular system within the stem to reduce competition between inflorescences. Key words: faba bean, flower abscission, pod abscission, path analysis, Vicia faba.

126 THE RELATION OF PEPPER FLOWER AND FLOWER BUD ABSCISSION WITH BUD CARBOHYDRATE AND ACC CONTENT

When bell pepper plants are subjected to high temperatures or low irradiance during flowering, abscission of flowers and flower buds can be severe enough to limit yields. Both types of stresses may lead to reduction of carbohydrate levels in the reproductive structures, and evolution of the abscission-causing hormone ethylene. In two greenhouse experiments, plants were subjected to combinations of 30 or 20 C air temperature and unshaded or heavily shaded conditions for one week at anthesis of the first flower. In a third experiment, plants were subjected to total darkness and temperatures of 30, 20 or 15 C for one week at the same stage of growth. In all experiments, levels of soluble carbohydrates and starch declined under low or zero light conditions, with rate of decrease proportional to the air temperature. Abscission of reproductive structures was not well correlated with carbohydrate levels: in spite of low sugars and starch, plants darkened for 7 days at 15 C showed no abscission. Levels of the ethylene precursor ACC in the buds, though variable, rose just before abscission began, but remained low in non-abscising treatments.

High temperature effects on pod and seed production as related to hormone levels and abscission of reproductive structures in common bean ( Phaseolus vulgaris L.)

Pod and seed numbers of Phaseolus vulgaris L. were markedly reduced by exposure to a high temperature (HT) of 32 27 ° C (day/night) for 5 days at anthesis. The reduction was caused by an increased abscission of flower buds, flowers and young pods, and by the failure of fertilization and seed development. Bean cultivars differed in their heat tolerance, as indicated by the relative decrease of pod and seed numbers at HT, compared with control plants at 22 17 ° C . HT decreased the amounts of indol-3yl-acetic acid (IAA) exported to agar (exp-IAA) from flower buds, flowers or young pods. This effect was more pronounced in the flowers. A positive correlation ( R = 0.922) was observed between the relative (%) adverse effects of HT on pod number and on exp-IAA from flowers, i.e. cultivars with a higher tolerance to HT of pod production had a smaller relative reduction in exp-IAA. No consistent relationships were found between the effects of HT on abscisic acid (ABA) levels and on yield parameters, or between ABA and exp-IAA.

Reproductive Abscission and Yield Response of Soybean to Root and Canopy Competition

AbstractInterplant competition has been shown to influence plant architecture and seed yield. However, the influence of individual root or canopy competition on soybean [Glycine max (L.) Merr.] yield has not been identified. Field studies were conducted to determine the effects of root and canopy competition on abscission of reproductive structures and seed yield of the soybean cultivar Forrest. Plots were established on a Captina silt loam (fine‐silty mixed mesic Typic Fragiudults). Treatments were (i) no competition (ii) root competition only (iii) canopy competition only and (iv) both root and canopy (combined) competition. There was no difference among no, root, and canopy competition in the total number of reproductive structures produced and retained in 1985. However, in 1986 root and canopy competition resulted in an average of 281 and 166 reproductive structures produced and retained, respectively. In both years, combined competition caused the greatest reduction in the number of reproductive structures produced and retained. Combined competition resulted in 52 and 58% abscission in 1985 and 1986, respectively. In 1985, no, root, and canopy competition had similar effects on pod number per plant with an average of 387 pods, while combined competition resulted in only 99. In 1986, however, no competition resulted in the largest number of pods (310), combined competition resulted in the smallest number of pods (34), and root and canopy competition were intermediate with an average of 184 pods per plant. Subjecting plants to root competition decreased total seed weight and total seed number per plant by 44 and 42%, respectively, while canopy competition reduced total seed weight and number by 78%.

THE SEARCH FOR IMPROVED LIMA BEANS YIELDS: A STARTING POINT

Delaware lima bean yields have averaged 1700 lbs per acre for the last 30 years. California averages 3500-4000 lbs per acre. Varieties M-15 and 1072 are used by both states for production. In an effort to increase lima bean yields in Delaware, the evaluation of the effect of weather events on plant development, the relationship of ethylene and abscission of reproductive structures, and the comparison of both California and Delaware lima bean production is being conducted. Preliminary observations of 1991 data show a difference in plant size and population between the two states. Although pods per plant are the same in both states, the number of pods per acre is greater in California. California yielded 4303 lbs. per acre and Delaware 1651 lbs. per acre. The average maximum and minimum temperatures in California was 92.7 and 60.7 degrees Fahrenheit respectfully compared to 83.1 degrees and 61.2 degrees Fahrenheit in Delaware.

Flower and Fruit Development in Tepary Bean

The drought-adapted, disease-resistant tepary bean (Phaseolus acutifolius A. Gray. var. acutifolius) is of great value as a potential gene donor of useful traits to the common bean (P. vulgaris L.). Analyses of flowering and fruiting patterns of tepary indicate that anthesis and abscission of reproductive structures within a raceme follow well-defined spatial and temporal patterns. Flowering occurs acropetally, and the probability of flowering decreases with distance from the most basal bud of the raceme. The probability of bud or pod abortion increases with distance from the basal bud, and the rate of abortion is highest in buds and pods proximal to the apex. Buds that never reach anthesis abort in the green-bud stage of development and aborting fruits cease development within the first 25% increase in pod length. In nonaborting fruits, the rate of seed abortion is 6%. A marked increase in abscission of all buds and fruits at all raceme nodes occurs before cessation of flowering.

Effect of Raceme‐Localized Supplemental Light on Soybean Reproductive Abscission1

The percentage of soybean [Glycine max (L.) Merr.] reproductive structures that abscise is a potentially important yield factor. To better understand the involvement of light in the abscission of reproductive structures, a series of in vitro raceme‐culture and growthchamber experiments were conducted. In the in vitro raceme‐culture experiments, racemes with four to six flowers at or past anthesis were excised from the soybean plant (genotype 1X93‐100), embedded in a complete nutrient, solid agar medium, and subjected to various light treatments. A series of three experiments indicated that the racemes contain a photoreceptor, possibly phytochrome, capable of regulating sucrose accumulation. In each of the growth chamber studies, supplemental light was supplied directly to individual soybean flowers via fiber optic light guides. The light source (a tungsten filament bulb) increased the photon flux to the flowers by 10‐fold. The first growth chamber experiment showed that flowers receiving supplemental light were more intense sinks for 14C‐sucrose than were controls (intensity value of 1.0 vs. 0.4 ✕ 10−7, intensity = [dps of flower/dps of raceme]/[kg dry wt of flower]). In a second study, 42% of flowers treated with supplemental light set pods, while only 26% of control flowers set pods. A third experiment showed that red supplemental light produced 55% fruit set, compared to 41% set for far‐red light, and 35% for controls (far‐red not statistically different than control, but all other comparisons are significantly different). These experiments indicate that both photoassimilate accumulation and abscission in young soybean reproductive structures may be regulated by light quality.

Flower and pod production inPhaseolus vulgaris

SummaryA series of glasshouse and growth-cabinet experiments were carried out to investigate aspects of flower and pod production inPhaseolus vulgarisL. (French bean). Abscission of flowers and immature pods varied between 45 and 80% in the seven cultivars tested, with flowers which opened first being most likely to produce mature pods. Seed yield was only slightly reduced and sometimes increased by the removal of opened flowers for periods of up to 15 days from the start of anthesis depending on the conditions under which plants are grown. It was demonstrated that plants compensated for flower removal by setting pods from flowers which opened later. Similarly, when opened flowers were removed from alternate nodes plants compensated by setting pods from flowers which opened on nodes not being deflowered.The physiological basis for premature abscission of reproductive structures in grain legumes is discussed.

Effects of Ethephon on Abscission of Vegetative and Reproductive Structures of Phaseolus vulgaris L.1

Abstract (2-Chloroethyl)phosphonic acid (ethephon) at 250 ppm controlled bud and flower abscission but not young pod abscission of ‘Dark Red Kidney’ bean. Leaf abscission was unaffected, intemodal elongation was temporarily retarded, and the number of seeds but not the number of pods produced exceeded that of untreated plants but the difference in seed production was not significant. Treatment with 500 ppm ethephon resulted in a pattern of abscission similar to that of untreated plants. At higher concentrations (1000 and 2000 ppm) abscission of reproductive structures and of leaves was promoted. Seed production, seed maturity, and seed size were reduced. New leaves were pendant and were smaller than those of untreated plants.