Pod Density Research Articles

Limitations to seed yield in short-duration pigeonpea under water stress

Yield components were determined for two short-duration pigeonpea [Cajanus cajan (L.) Millsp.] cultivars, ICPL 87 and ICPL 151, in response to terminal drought stress with three partial flower/pod removal or four foliar fertilization treatments applied from the time of full flowering. Flower/pod removal treatments comprised a control with no flower/pod removal, lower-plant flower and pod removal at full flowering and 18 days later (EL), allowing pods to develop only on the top-3 nodes of the main stem, and flower/pod removal 18 days after full flowering only (L). The EL and L treatments were applied to ICPL 87 and only the EL treatment to ICPL 151. Seed yield of the top-3 nodes was increased by the EL treatment for both cultivars under rainfed and irrigated conditions, but was not significantly affected by the L treatment. With flower/pod removal, increased yields of the top-3 nodes were due to increases in the pod density and/or the seed size, with little change in the number of seeds pod−1. Foliar fertilization of cultivar ICPL 87 with solutions containing N, P, K and S in similar proportions to those found in developing seeds at 20 and 40 kg N ha−1, had no significant effects on yield or yield components under either soil moisture condition. Factors within the plant during early reproductive growth appear to limit seed yield under both soil moisture conditions, and reproductive sink capacity and nutrient (N, P, K and S) supply, apparently, are not limiting. Such information on plant factors limiting yield under water stress conditions allows for a better understanding of drought resistance mechanism(s) for short-duration pigeonpea.

Quantitative analysis of pod formation, seed set and seed filling in winter oilseed rape ( Brassica napus L.) under field conditions

Pod formation, seed set and seed filling of winter oilseed rape ( Brassica napus L.) were studied in two field experiments with the variety Jet Neuf. Variations in total dry matter production (source size) and pod density (sink size) were established by varying seed rate, plant density, sowing date and the application of shading. od formation and seed set per pod were recorded on different branches, at various heights in the canopy and on pods initiated at different times during flowering. Pod density and seed density appear to be fully determined just after the end of flowering. The potential number of pods (i.e. the number of flower buds) did not appear to be a limiting factor, as at all positions in the canopy it was much higher than the number attained. Averaged over the whole canopy, pod set varied between 43 and 58%. Potential and actual pod density were linearly related to cumulative dry matter production of the crop until the onset of flowering and until the end of flowering, respectively, i.e. to total assimilate availability over that period. The number of seeds per pod did not vary with height in the canopy. Primary branch number and the time of pod initiation during flowering had some effect on the number of seeds per pod; however, this had little influence on the overall mean number of seeds per pod of the whole canopy and did not affect the differences among treatments. A linear relationship was found between seed density and dry matter production of the crop during flowering. Individual seed weight followed a sigmoid pattern when plotted against the temperature sum from the onset of flowering per flower bud until maturity. The pod hulls were the only competing sink during early seed fill and remobilization of reserve carbohydrates contributed at most 12% to final seed yield.

Effect of irrigation on water use, water-use efficiency, growth and yield of mungbean

Mungbean ( Vigna radiata (L.) Wilczek) was grown on sandy loam soil (typic Ustochrepts) under four irrigation schedules: irrigation at cumulative evaporation from USWB Class A pan equal to 200 mm (I 200), 300 mm (I 300), 400 mm (I 400) and no post-sowing irrigation (I 0) during a summer season (April–June) in India. The experiment was planned to study changes in soil water, growth and productivity in relation to irrigation schedules for efficient utilization of limited irrigation water in mungbean. Water use increased with frequency of irrigation and comprised 61, 55, 50 and 25% of pan evaporation during the growing season in I 200, I 300, I 400 and I 0 irrigation schedules, respectively. Water extraction decreased with soil depth in all the irrigation schedules. However, the plants extracted more water from deeper soil layers in the I 300 adn I 400 than in the I 200 I 0 schedules. The highest water-use efficiency was recorded in I 0, followed by I 300, I 400 and I 200. The leaf area index, crop growth rate, biomass, seed yield and partitioning of dry matter from above-ground plant parts to grains were significantly higher in I 300 followed by I 400, I 200 and I 0. The I 400 schedule had the highest harvest index. Seed yield was controlled primarily by pod density, while variation in seed size and grain number per pod had little influence on grain yield. The study has shown that irrigation at 300 mm pan evaporation is more beneficial, in terms of water economy and productivity, than the frequent watering at 200 mm pan evaporation in mungbean.

Effect of triapenthenol plant-growth regulator on canola height, yield, side branches and pod density

A 3-yr field experiment was conducted at the Scott Experimental Farm to determine the effect of the growth regulator, triapenthenol, on the growth and development of Argentine canola (Brassica napus L.). Triapenthenol reduced plant height 25–45 cm under optimal growing conditions. Increases in yield, branches and total pods were observed. Application at the bud stage was more effective than earlier treatment in the rosette. It was concluded that triapenthenol application to canola could be a useful management tool, particularly under optimal growing conditions.Key words: Canola, growth regulator, RSW-0411, lodging

The Influence of Neighboring Hosts on Colonization of Prairie Milkweeds by a Seed‐Feeding Bug

At Konza Prairie, Kansas, milkweeds (Asclepias viridis) were mapped and censused repeatedly to examine the influence of neighboring conspecifics on colonization of individual host plants by adults of the seed bug Lygaeus kalmii. Analysis by multiple regression suggests that the primary determinant of abundance of adult bugs on a host plant was the plant's own pod (seed) production; abundance of adult bugs also increased, however, with increasing pod production by adjacent plants. This neighborhood effect was limited to plants immediately adjacent to a host plant; pod density >3 m distant from hosts had little influence on colonization of hosts by bugs. Mark—recapture studies revealed differences in responses of the two sexes of L. kalmii to neighboring pod density: males lingered longer, while females lingered less on individual plants when these plants were surrounded by many vs. few pods. Damage from L. kalmii sustained by milkweeds thus results from a complex interplay of reproductive behaviors of individual host plants, their neighbors, and their seed predators.

Drought Adaptation of Cowpea. I. Influence of Drought on Seed Yield1

AbstractField studies were conducted to determine cowpea [Vigna unguiculata (L.) Walp.] response to different intensities of drought at different stages of growth to guide programs for the development of improved cultivars and improved management practices for semi‐arid zones.Two cowpea cultivars were subjected to different levels of irrigation using a line‐source sprinkler system in the field on a coarse‐loamy, mixed, thermic Haplic Durixeralf soil during 2 years with contrasting weather patterns. Well‐watered plants were irrigated weekly. In other treatments, water was not supplied during either the vegetative, flowering, or pod filling stages.Dry seed yields of well‐watered treatments were negatively correlated with degree days above 35 C during flowering.Yields of both cultivars were not reduced by drought during the vegetative stage, compared with the weekly irrigated treatment, providing subsequent environmental conditions were conducive to rapid recovery of growth and efficient pod set. Drought during the flowering stage substantially reduced yields, but partial yield recovery was observed where drought caused all flowers to abscise and the subsequent environment, after irrigation was resumed, permitted a new flush of flowers to produce pods. Drought during pod filling substantially reduced yields of both cultivars in both years.Variations in yield due to environmental stresses were mainly due to variations in number of pods/m2 except for drought during pod filling which resulted in both low pod density and small seed. Yield with abundant water or drought during pod filling appeared to be partially source limited, whereas intermediate levels of drought at other stages may have resulted in sink limitations on yield because these treatments produced the heaviest seed.

Effect of Host Plant Density on Populations of a Specialzied, Seed‐Sucking Bug, Oncopeltus Fasciatus

To assess the role of host plant density in the life of a specialized herbivore, natural populations of the large milkweed bug, Oncopeltus fasciatus, were monitored in 5 paired study plots of high and low milkweed density (Asclepias syriaca). At all sites the plot with a higher density of milkweed pods supported more O. fasciatus per pod. At some sites, O. fasciatus load (cumulative biomass of bugs/pod) correlated positively with pod density within plots, and milkweed below a certain density escaped O. fasciatus exploitation. However, at a site that recevied an exceptionally large influx of colonizing bugs, almost all pods were heavily fed upon, regardless of their dispersion. This herbivore clearly demonstrates the resource—concentration effect. The effect orginates with the oviposition patterns of colonizing ♂ ♂ and its strengthened by differential mortality of nymphs searching for suitable feeding spots. Since these behaviors are common in other insects herbivores, the resource—concentration effect may be an important organizing factor in many natural, as well as cultivated plant—athropod associations.