Pod Growth Research Articles

Flower and pod production at various nodes of Phaseolus vulgaris L.

SUMMARYIn a glasshouse study, the pattern of flower and pod production at the various flowering nodes of Phaseolus vulgaris (cv. 344) was mapped out. Soft X-radiation techniques were also used to study the development of retained and abscissed pods at the various nodes while varying levels of flower or pod removal were used to study the modification to pod development at each flowering node following organ removal.The period of flower opening over the whole plant spanned an average of 12 days and 90% of the pods retained to maturity were formed from flowers opened within 4 days of anthesis. The terminal inflorescence produced most of the flowers on the plant (25%), but nodes 2 and 3 developed the bulk (50%) of the pods retained. Only 30% of the open flowers on the plant formed pods that were retained to maturity.Pod elongation was initially very rapid in the pods to be retained, following successful fertilization, with the latter period of pod growth devoted almost entirely to seedfilling. A slow growth rate characterizes the development of abscission in Phaseolus pods and the number of seeds per pod is determined later in pod growth.Flower or pod removal prolonged flowering and led to longer leaf retention and more branches on the main stem. The number of mature pods was lower on the treated plants and the more severe the removal the larger were these treatment effects. Plants compensated for fewer pods by having more seeds per pod but these were not enough to prevent significant depression of seed dry weight per plant by the most severe removals. Flower or pod removal led to a shift of emphasis in pod production by the plant from nodes 2 and 3 to other areas of the plant where natural wastage of flower and young pods is high.

A quantitative assessment of larval infestation level required for intensive screening of cowpea for resistance to the black cowpea moth, Cydia ptychora (Meyrick) (Lepidoptera: Tortricidae)

Assessment of the damage potential of Cydia ptychora (Meyrick) was carried out in Ife Brown cowpea at different levels of larval infestation and different pod growth phases. The results showed that C. ptychora caused significant shrivelling in pods of Ife Brown cowpea when infested with either one, two or three first-instar larvae per pod at either the young or mid-fill growth phases, relative to the corresponding controls. A significant reduction in seed yield was also recorded in plants subjected to an infestation level of either one, two or three first-instar larvae per pod at both mid-fill and mature pod growth phases. Thus, an infestation level of one first-instar larva per pod at either the mid-fill or mature pod growth phases would be adequate for intensive screening of cowpea varieties for resistance to C. ptychora, using Ife Brown as a standard for comparison.

Development of Reproductive Structures in Grain Legumes: The Growth, Cell Structure and Maturation of Pods and Seeds

SUMMARYThe study was carried out in an unheated glasshouse under natural conditions of daylength and temperature. Rates of pod and seed growth and development, and of desiccation at maturity, are reported in single genotypes of Lupinus albus, Lupinus mutabilis, Vicia faba, Pisum sativum and Lathyrus latifolius. The histology of tissue layers in pods are also described. The culti-var of Pisum sativum completed dry weight accumulation in pods in 20 days from anthesis; the equivalent time in Lupinus albus (Kievskij mutant) was 60–70 days and in genotypes of Lupinus mutabilis and Vicia faba about 50 days. The heavier pods and seeds of the L. albus and V. faba cultivars were due to a prolonged rapid growth phase: rates of weight accumulation in seeds during the rapid growth phase were similar for all cultivars. The histology of the pod wall varied between species but the rate of dehydration of pods was not a factor in determining date of maturity. The results are discussed in the light of reservations based on known intra-specific variation in crop species.

Interspecific hybridization between Vicia faba (L.) and Vicia narbonensis (L.): Early pod growth and embryo-sac development

Fertilized embryo-sac development and pod growth was studied in one Vicia faba cultivar, one Vicia narbonensis population and their reciprocal crosses. The initial development of endosperm and embryo was at least four days faster in V. narbonensis than in V. faba. Pods and ovules developed also faster in V. narbonensis than in V. faba. The growth rate of the hybrid pods followed the growth rate of the mother species, but was slower than that of the pods from selfed flowers. In the cross V. narbonensis × V. faba the ovules stopped growing 9 days after pollination, while in the reciprocal cross they stopped growing 15 days after pollination. Hybrid embryo-sacs from V. faba × V. narbonensis were aborted before they reached the stage of 256 endosperm nuclei or 200 embryo cells. Selfed V. faba embryo-sacs reached this stage in less than 9 days after pollination. In the reciprocal cross the embryo-sacs were aborted before they reached the stage of 128 endosperm nuclei or 80 embryo cells. Selfed V. narbonensis embryo-sacs reached this stage at the 4th day after pollination. Given that at these stages the embryo has less than 200 cells it was concluded that an in-ovule embryo culture technique should be developed to obtain hybrid plants.

Symbiotic N2 fixation in pea and field bean estimated by15N fertilizer dilution in field experiments with barley as a reference crop

The total amount of nitrogen derived from symbiotic nitrogen fixation in two pea and one field bean cultivar, supplied with 50 kg N ha−1 at sowing (‘starter’-N), was estimated to 165, 136, and 186 kg N ha−1, respectively (three-year means). However, estimates varied considerably between the three years. At the full bloom/flat pod growth stage from 30 to 59 per cent of total N2 fixation had taken place. The proportion of total N derived from N2 fixation at maturity was higher in seeds than in vegetative plant parts and amounted to 59.5, 51.3 and 66.3 per cent of total above-ground plant N in the two pea cultivars and field bean, respectively (three-year means). The recovery of fertilizer N was 62.2, 70.2, 52.1, and 69.5 per cent in the two pea cultivars, field bean and barley, respectively. Growth analysis indicated that barley did not meet the claims for an ideal reference crop in the15N fertilizer dilution technique for estimating N2 fixation in pea and field bean. ‘Starter’-N neither increased the seed yield nor the N content of the grain legumes.

The influence of rate and time of nitrate supply on nitrogen fixation and yield in pea (Pisum sativum L.)

The influence of nitrate N supply on dry matter production, N content and symbiotic nitrogen fixation in soil-grown pea (Pisum sativum L.) was studied in a pot experiment by means of15N fertilizer dilution. In pea receiving no fertilizer N symbiotic nitrogen fixation, soil and seed-borne N contributed with 82, 13 and 5% of total plant N, respectively. The supply of low rates of nitrate fertilizer at sowing (“starter N”) increased the vegetative dry matter production, but not the seed yield significantly. Nitrogen fixation was not significantly decreased by the lower rates of nitrate but higher rates supplied at sowing reduced the nitrogen fixation considerably. Applying nitrate N at the flat pod growth stage increased the yield of seed dry matter and N about 30% compared to pea receiving no nitrate fertilizer. Symbiotic nitrogen fixation was reduced only about 11%, compared with unfertilized pea, by the lowest rate of nitrate at this application time. The pea very efficiently took up and assimilated the nitrate N supplied. The average fertilizer N recovery was 82%. The later the N was supplied the more efficiently it was recovered. When nitrate was supplied at the flat pod growth stage 88% was recovered, and 90% of this N was located in the seeds.

Relationship of developing pods with photosynthetic characteristics of leaves in chick pea

Net photosynthesis rate, ribulose-1,5-bisphosphate carboxylase activity, ribulose-1,5-bisphosphate carboxylase protein and total chlorophyll content in leaves which subtend the pods vis-a-vis the pattern of pod, podwall and seed growth were analyzed in chick pea. Three sets of plants namely control, deflowered and depodded were maintained. Accompanying the initiation of pod development in control plants, there was a decline in these photosynthetic characteristics in leaves of control as well as deflowered plants. The senescence rate was higher in control plants compared to plants from which flowers or pods had been removed. The early pod growth which was mainly constituted by podwall growth, was accompanied by a higher decline in leaf net photosynthesis rate. Ribulose-1,5-bisphosphate carboxylase activity and ribulose-1,5-bisphosphate carboxylase protein decreased predominantly at the later stage of pod growth, which was mainly constituted by higher seed growth. Loss of chlorophyll was also higher at later stages of pod growth. It is suggested that both nutrient remobilization and hormonal action are probably involved during monocarpic senescence in chick pea.

Senescence of detached leaves in pigeon pea and chick pea: Regulation by developing pods

The senescence rate of the subtending leaves in deflowered and control plants of pigeon pea ICajanus cajan (L.) Millsp. cv., Prabhat] and chick pea (Cicer arietinum L. cv. JG 62) were examined during the course of natural and induced senescence, at several stages of pod growth. The leaves from the top 5 nodes on the main axis in pigeon pea and the top 8 nodes on the main axis in chick pea were used throughout the experiments. The natural senescence was characterized in leaves taken directly from the field‐growing plants. For the study of induced senescence, the leaves were excised from both control and deflowered plants at various stages of pod growth and placed in test tubes containing water under dark conditions. Senescence was assessed in terms of peroxidase activity and contents of tola] chlorophyll, soluble amino acids and total protein. During natural ageing in the field, the leaves from deflowered plants exhibited delayed senescence in both the species. In contrast, the rate of ageing during induced senescence was higher in the leaves of deflowered plants than in the controls. Although of the same chronological age when excised for induced senescence, the leaves of deflowered plants were evideatly metabolically different from the controls, due to the fact that deflowered plants did not support the development of pods. This difference probably determined the subsequent rate of induced senescence.

Effects of Tobacco Budworm (Lepidoptera: Noctuidae) Infestations on Pod Damage and Yield Loss in Soybean

Field plot studies from 1977 to 1980 were conducted to determine the effect of Heliothis virescens (F.) infestation on soybean. Larval infestations were established at various levels and times by applying eggs in a spray. The amount of damage and its effect on yield depended on the timing as well as the intensity of infestation. The only infestations that reduced yield were produced by egg application during full bloom. Resultant larvae were fifth or sixth stage during the full pod growth stage. They destroyed more seed than comparable larvae during other plant growth stages. The period during soybean bloom when egg application resulted in this critical synchrony was 1 week long.

Occurrence of 4-Cl-Indoleacetic Acid in Broad Beans and Correlation of Its Levels with Seed Development

Seeds and leaves of Vicia faba L. contain considerable amounts of 4-Cl-indoleacetic acid as determined by gas-liquid chromatography and gas-liquid chromatography-mass spectrometry. The unchlorinated auxin could not be detected in either leaves or seeds at different stages of development. The developmental stages of fruits and seeds were characterized by the rate of straight growth of pods, the rate of fresh weight increase, and the development of the endosperm. The peak of 4-Cl-indoleacetic acid content per seed coincides with the maximum rate of water accumulation in the seeds.

Influence of plant density, nitrogen, water supply and pod or leaf removal on growth of oilseed rape

Two species of oilseed rape ( Brassica campestris cv. ‘Torch’ and B. napus cv. ‘Tower’) were grown in a controlled environment room at two plant densities, three levels of nitrogen fertilization, and three levels of irrigation. Pods or lower leaves were removed at flowering. Growth of all plants parts was less at the high plant density although pod growth was least affected. Leaf growth was particularly responsive to nitrogen treatment while stem and pod growth were more responsive to irrigation level. The interaction of nitrogen fertilization and irrigation level confirms that a single limiting factor would prevent growth responses to other environmental factors. Defoliation led to slight reductions in pod, stem and root growth while pod removal led to increases in root, stem and leaf growth.

Agronomic assessment of snap beans (Phaseolus vulgaris) in a warm-temperate semi-arid environment

SUMMARYThe production of green beans was studied in sowings made from December to February, September to February, and from October to February in three seasons, and over six oonsecutive seasons for a mid-season sowing.With September-October sowing the rate of emergence was slow, and establishment sometimes poor. Possible virus disease, and the lack of continuity of setting pods resulting from cool weather, were problems. Good yields were obtained from midseason sowings (31 October-18 December), up to 19·6 t/ha, with good yields for late sowings up to 13·9 t/ha in ^he first three seasons. In another three seasons mid-season sowings (late November-early December) resulted in poor yield due to periods of hot weather (> 35 °C max.) prior to and during flowering.There was a relationship between quality and yield. The greatest yield and best quality green pods were obtained when conditions favoured rapid growth and rapid setting of pods, and when there was a high rate of pod maturation.For yield of dry seed the early sowings were best, 3·6 and 2·8 t/ha in two seasons. A total of 460 mm of water was required for the first six sowings, but fell to 360 mm for the mid-February sowing (rainfall plus irrigation).Although it was possible to grow beans over a 9-month period the January and early February sowings appeared to be the least risk prone with the present cultivars.

Effects of Irrigation on Accumulation of Soil and Symbiotically Fixed N by Soybean Grown on a Norfolk Loamy Sand1

AbstractIn the southeastern Coastal Plain, soybean [Glycine max (L.) Merr.] is normally grown on soils that are often exposed to drought and leaching rains as well as being low in available N. A field study was conducted to evaluate the impact of water management on accumulation of soil and symbiotically fixed N by soybean grown on these type soils. Nodulating and nonnodulating isolines of ‘Lee’ cultivar soybean were grown under irrigated and nonirrigated conditions in 1979 and 1980 on a Norfolk loamy sand (fine‐loamy, mixed, mesic Typic Paleudults). A period of excessive rainfall occurred in 1979, while a major drought occurred in 1980. Irrigated treatments had lower soil‐NO‐3 concentrations in the Ap horizon than nonirrigated treatments during 1979, but there was no effect of irrigation on soil NO‐3 in 1980. Dinitrogen fixation, as estimated by the difference in N accumulation between nodulating and nonnodulating isolines, accounted for 76 to 91% of total plant N in the irrigated plots and 55 to 60% in the nonirrigated plots. Estimates of total plant N fixed exceeded 1100 mg/plant for the irrigated plots in 1979 and 1980. Maximum N accumulation for the nodulating isoline occurred in the nonirrigated plots in 1979 and in the irrigated plots in 1980. However, the nonnodulating isoline had maximum accumulations of both N and dry matter in the nonirrigated treatments in both 1979 and 1980. The number of nodules/plant and the C2H2‐reducing activity were significantly higher in the irrigated plots during the pod growth stages in 1980. Irrigation did not significantly affect seed yield of nodulating Lee soybean in 1979, but did result in a twofold increase in 1980. The effects of irrigation on the Lee nonnodulating isoline resulted in a positive yield response in 1980, but a negative response in 1979. These findings show that a major portion of the N‐requirement for soybean in the southeastern Coastal Plain is met by fixation and that the relative importance of fixed N may vary substantially with rainfall patterns and irrigation.

The use of radiography in studies of plant development in vivo

The growth and development of individual pods in plants of oil-seed rape (Brassica napus L.) were followed from anthesis onwards using a soft X-radiation in-vivo technique. Changes in the length and width of pods and in the positions, numbers and sizes of seeds within them were determined quantitatively from X-ray plates and photographs. The technique provides a valuable and as yet unexploited tool for studies of plant development.

VARIABILITY IN POD FILLING CHARACTERISTICS OF PEAS (Pisum sativum L.) UNDER FIELD CONDITIONS

The average rates of pod dry weight increase, final pod weights and durations of pod growth were estimated for peas (Pisum sativum L.) growing in the field. The effects of plant genotype, field location and the time of season on these characters were studied in several populations of pea genotypes. Rate of pod filling and final pod weight were both affected by genotype, year and initiation time during the season. Effective duration of pod filling was not affected by any of these factors and final pod weight was always strongly related to the rate of filling. For 46 genotypes, the rate of pod filling ranged from 16 to 75 mg∙day−1 in a single location. Despite the large environmental and seasonal variation, the interactions with genotype were small and estimates of broad sense heritability were high. Across genotypes, rate of pod filling was correlated with weight per 100 seeds and final seed yields. The large changes in rate of pod filling during the season were similar in pattern in 2 yr. However, because this pattern was similar in populations with different flowering times, and because of the significant relationship to the changes in irradiance during both seasons, it is suggested that these seasonal changes in pod filling are of environmental rather than developmental origin.Key words: Pod bulking, seed development, pod development, seasonal changes, growth rate, duration

RELATIONSHIPS BETWEEN HOST AND ENDOPHYTE DEVELOPMENT IN MYCORRHIZAL SOYBEANS

SUMMARYSymbiotic associations of soybeans and the vesicular–arbuscular mycorrhizal fungus Glomus fasciculatus were grown to maturity in a sand‐perlite rooting medium watered with a nutrient solution containing growth‐limiting amounts of soluble phosphorus. Development of fungal mycelia external and internal to the host plant's root system was measured by determining chitin in isolated fungal mycelium, in the rooting medium, and in the mycorrhizae. The biomasses of the extra‐ and intraradical mycelia were calculated from the values of chitin obtained spectrophotometrically. The amount of total fungal biomass relative to that of the host plant varied throughout the lifespan of the association and reached a maximum of 2.3 % 10 weeks after planting. The amount of intraradical mycelium increased throughout the host plant's life span. Extraradical fungal structures attained a maximum weight at the onset of logarithmic growth of the soybean pods and decreased thereafter. Cessation of the rapid growth phase of G. fasciculatus lagged behind that of the host plant's vegetative structures, but appeared to be related to pod development. The fungus to root dry wt ratio was 12–3% at senescence. The ratio of extra‐ to intraradical mycelium decreased throughout the association's lifespan. Since the extraradical hyphae are the organs responsible for enhanced nutrient uptake this ratio is proposed as an index of the endophyte's usefulness to the host. High values for this usefulness index coincided with significant growth enhancement of the host plant. Source–sink relationships in the host appear to be a determining factor in the growth of the fungal endophyte.

Paleomagnetism of the Moenkopi Formation, Colorado Plateau: Basis for long‐term model of acquisition of chemical remanent magnetism in red beds

Paleomagnetic studies of Moenkopi samples from several sites on the Colorado Plateau, including a complete 427‐m section at Sinbad Valley, western Colorado, reveal the following: (1) the presence of both normal and reversed Triassic components in many of the same samples at many localities, (2) the close correlation of the magnetic polarity and intensity of magnetic remanence with the lithologic characteristics in the Sinbad Valley section, (3) a streaked pattern of the remanence directions in any one member in the Sinbad Valley section similar to that expected from polar wander, (4) a lack of progressive change from the base upward, and (5) the common intermediate remanence directions of weak intensity (suggesting the presence of two or more nearly balanced anti‐parallel components) throughout the formation. The results of our investigation, combined with previously reported petrographic and paleomagnetic studies of the Moenkopi Formation, have led us to conclude that the principal remanence carried by the formation is chemical remanent magnetism (CRM) acquired diagenetically over a geologically long time interval. From the available data we have formulated the following model to explain how the CRM was acquired through natural processes acting intermittently at geologically reasonable rates. When initially deposited, the Moenkopi sediments consisted primarily of first‐cycle detritus containing a few percent of iron‐bearing accessory minerals such as biotite, hornblende, magnetite, and ilmenite. At some time after deposition, under favorable subsurface conditions, intrastratal alteration began, involving breakdown of iron‐bearing silicate and oxide minerals, partial replacement of some iron‐rich silicate grains by hematite, martitization of magnetite, growth of hematite pods and blebs in ilmenite and biotite, and precipitation of crystalline hematite in both primary and secondary voids. The authigenesis spanned at least two polarity events and probably continued over several tens of millions of years. Stratigraphic units with grossly similar lithologies underwent similar diagenetic alterations at rates and to extents that were different from other stratigraphic units having different lithologies. Because of variations in the rate and duration of alteration and variations in the length of normal versus reversed polarity events, any given lithologic unit tended to be dominated by one polarity. The model given above seems to be capable of explaining not only those magnetic and petrographic features found in the Moenkopi Formation but also those of most other red beds.

An analysis of the growth of mung beans at a range of plant densities in tropical Australia. II. Seed production

An analysis of seed production by crops of Vigna radiata cvv. Berken and CES-ID-21 and V. mungo cv. Regur, grown at a range of plant densities, indicated that the proportion of carbon assimilated during pod-filling and partitioned to the seed varied in such a way that seed yield at maturity was relatively unaffected by plant density. Seed yield of Regur was much higher than that of either Berken or CES-ID-21, and this could be attributed primarily to the longer duration of pod-filling in Regur rather than to any differences in potential pod growth rates. The data support the hypothesis that during the period of pod initiation, each viable pod requires a critical rate of supply of assimilate, and suggest that this critical rate of supply is less for V. mungo than for V. uadiata. Whilst pod number, and hence seed yield, was determined by the rate of assimilate supply during the period of pod initiation, not all the dry matter accumulated during pod-filling was partitioned to the pods. Hence seed yield in these mung bean cultivars does not appear to be determined solely by assimilate supply during pod-filling.

Effects of Defoliating Pests on Soybean Canopy CO2 Exchange and Reproductive Growth1

Defoliation during reproductive growth of soybean [Glycine max (L.) Merr.] may significantly reduce yields. The objective of this study was to elucidate the relationships among organism‐induced defoliation, CO2 exchange rates, and reproductive growth in fieldgrown soybean. Soybean (‘Bragg’) plots were sprayed a factorial design with diflubenzuron (0.035 kg a.i./ha) and a benomyl‐maneb mixture (1.12 a.i./ha) on two dates, first at early flowering (5 August) and again at early pod set (19 August). Diflubenzuron application prevented defoliation by velvetbean caterpillar (Anticarsia gemmatalis Hubner). By 12 September, LAI was reduced from 5.5 to 2.8, leaf dry weight from 185 to 110 g/m2, and midday light interception from 94 to 72% in defoliated as compared to non‐defoliated plots. While canopy specific leaf weight (SLW) increased in all treatments during the experimental period, SLW was 1.0 mg/cm2 higher in defoliated than non‐defoliated plots. On 4 September defoliated plots were sprayed with diflubenzuron (0.035 kg a.i./ha) and carbaryl (0.56 kg a.i./ha) prevent further leaf loss.Canopy CO2 exchange was measured at various photosynthetic photon flux densities (PPFD) to develop photosynthesis light response curves. Net canopy photosynthesis at 1,500 μE·m−2·sec−1 PPFD (PN1500) declined steadily in all treatments during seed growth. PN1500 and plant dark respiration, respectively, were reduced by 6.8 and 3.3 mg CO2·dm−2·hour−1 in defoliated compared to non‐defoliated plots. Soil CO2 efflux rates did not differ significantly (P < 0.05) between treatments. Differences in pod growth rates (7.6 and 9.21 g·m−2·day−1 and yields (434 and 502 g·m−2) between defoliated and non‐defoliated plots, respectively, were attributed to differences in canopy photosynthetic capacity. There was no apparent effect of defoliation on seed growth duration or seed abortion. Rather, yield reduction in defoliated plots was related primarily to slowing of the individual seed growth rate. Balance of carbon flux to seeds showed relationships between instantaneous canopy CO2 exchange measurements and sequential harvest data.

Photomorphogenesis of the Gynophore, Pod and Embryo in Peanut, Arachis hypogaea L.

Darkened excized gynophores ceased to elongate after 8–10 days in vitro and started to form a pod. Gynophore elongation was inhibited to a greater extent in total darkness than under low irradiance, while pod and embryo growth was stimulated in darkness only. Intact gynophores, enclosed in transparent vials containing glass beads, continued to elongate in both light and darkness. In light the elongating gynophores thickened as they penetrated between the glass beads, forming a seedless pod at the bottom of the vials. In the dark the elongating gynophores produced small pods in which the seeds had started to grow. Excized gynophores elongated in vitro under continuous white light at a rate similar to that of intact exposed gynophores. The rate of elongation in vitro, was lower under continuous blue or red-enriched light, than under white light, and was further reduced under continuous far-red irradiation. Pods did not form during any of the continuous irradiation treatments but only after transfer to darkness, the largest pods forming after continuous far-red irradiation. As little as 10 min daily exposure to red or far-red irradiance had the same effect on gynophore elongation as continuous irradiation. Pods formed only when the daily periods of far-red irradiation were 30 min or less. Reducing the daily exposures to 2 min decreased the time to onset of pod formation from 30 to 16 days. Far-red following red irradiation was effective in inhibiting gynophore elongation stimulated by red irradiation. Pod formation in red/far-red irradiation was only 50 per cent of that observed in far-red irradiation. The involvement of light in continual gynophore elongation and in the concomitant inhibition of proembryo growth is discussed.