Floral and pollination characteristics of Eriocaulon heleocharioides, an extinct species in the wild, for evidence-based conservation management.

Plant topping effects on growth, yield, and earliness of field-grown cotton as mediated by plant density and ecological conditions

High nitrogen application rate and planting density reduce wheat grain yield by reducing filling rate of inferior grain in middle spikelets

Shrubs as magnets for pollination: A test of facilitation and reciprocity in a shrub-annual facilitation system

Astrophytum asterias (star cactus) is an obligate outcrosser that does not reproduce vegetatively, so all reproduction is the result of inter-plant transfer of pollen by insects. By measuring seed set resulting from single pollinator visits, we evaluated effectiveness (mean seed set per visit) and importance of pollinator (effectiveness times frequency of visitation) of insects visiting flowers of A. asterias. Results indicate that the most common visitor, Macrotera lobata, is a relatively ineffective pollinator, while the less common Diadasia rinconis is the most effective and important pollinator. Two behavioral variables (duration of visit, whether or not visitors landed on the stigma) were assessed as possible predictors of fruit set. While duration of visit was not predictive of fruit set, there was a positive correlation between fruit set and the proportion of visits a visitor landed on the stigma when entering the flower.

Modern compared with older maize (Zea mays L.) hybrids tolerate more plant density stress, but more information is required on how modern hybrids interact with plant density. Field experiments were established in 1991 (warm‐dry) and 1992 (cool‐wet) to evaluate whole‐plant physiological, dry matter (DM), and grain yield responses of four commercial hybrids at low (4.5 plants m−2), medium (6.75), and high (9.0) plant densities. As plant density increased, leaf CO2 exchange rates (CER) declined 10 to 20% under mild and 20 to 30% under warm dry conditions. Compared with the high plant density, the low plant density had a 40% lower leaf area index from midvegetative to early grain filling, which offset higher photosynthetic efficiency, resulting in lower crop growth rates during vegetative development and 25% less DM accumulation at silking. When averaged across hybrids, the low plant density averaged 15% lower DM and grain yields than the high plant density. Hybrid ✕ plant density interactions were observed for DM and grain yields. The more prolific hybrid showed mostly linear DM and grain yield responses to plant density, whereas a single‐eared hybrid showed quadratic responses in both years. Another single‐eared hybrid, which did not respond to density, had low leaf CER at all densities, a reduction in kernels per plant at the medium density, and increased barrenness at the high plant density in 1991. Apparently, modern hybrids interact with plant density, regardless of growing conditions, and some modern hybrids do not tolerate density stress in dry years.

High plant density inhibits vegetative branching in cotton by altering hormone contents and photosynthetic production

Herbivory induces changes in plants that influence the associated insect community. The present study addresses the potential trade-off between plant phytochemical responses to insect herbivory and interactions with pollinators. We used a multidisciplinary approach and have combined field and greenhouse experiments to investigate effects of herbivory in plant volatile emission, nectar production, and pollinator behavior, when Pieris brassicae caterpillars were allowed to feed only on the leaves of Brassica nigra plants. Interestingly, volatile emission by flowers changed upon feeding by herbivores on the leaves, whereas, remarkably, volatile emission by leaves did not significantly differ between infested and non-infested flowering plants. The frequency of flower visits by pollinators was generally not influenced by herbivory, but the duration of visits by honeybees and butterflies was negatively affected by herbivore damage to leaves. Shorter duration of pollinator visits could be beneficial for a plant, because it sustains pollen transfer between flowers while reducing nectar consumption per visit. Thus, no trade-off between herbivore-induced plant responses and pollination was evident. The effects of herbivore-induced plant responses on pollinator behavior underpin the importance of including ecological factors, such as herbivore infestation, in studies of the ecology of plant pollination.

Syarifuddin, Hafnisiregar E, Jambak J, Suryani C. 2018. The impact of oil palm plantation on ecology of rambutan (Nephelium lappaceum) insect pollinators. Biodiversitas 19: 1347-1351. The establishment of oil palm plantation in Sumatra was the result of massive conversion of its rainforest. Many studies have shown that oil palm plantation is a main threat to biodiversity including insect pollinators. However, its effect on the ecology of insect pollinators is still poorly studied. In this study, we investigated the impact of oil palm plantation on the species richness and composition, abundance as well as pattern of time period and duration of insect visit on rambutan, Nephelium lappaceum, flowers. Insect visitors of flowers were compared between rambutan grown in the Oil Palm Plantation (OPP) ecotone and the one in the mixed Oil Palm Garden Forest (OPGF) ecotone. Number of visiting insects on each pannicle in ten minutes period and number of flowers and pannicles visited within 2 minutes were enumerated. The length of time of a randomly selected individual of the most abundant insects visited a flower and a pannicle was also recorded. The results showed that species composition of insect visitors was different between the two ecotones and total insect abundance was significantly higher on rambutan flowers located in the OPGF ecotone compared to rambutan trees grown close to oil palm plantation. The insect visitors on rambutan flowers in the OPGF ecotone were dominated by bees while in the OPP was dominated by Calliphorid fly. Among the main pollinators, the bee Apis cerana visited far more flowers and pannicles compared to Trigona sp and Chrysomya sp. Thus, more evidence showing that oil palm plantation probably has caused the disappearance of main species of bee pollinators, reduced abundance of flower-visiting insects, change of pollinator species composition, change of the pattern of time and change the duration of insect visit of rambutan flowers.

Interaction effect of nitrogen form and planting density on plant growth and nutrient uptake in maize seedlings

Plant species diversity could enhance plant productivity and pollutant removal efficiency in constructed wetlands (CWs). However, the potential importance of plant density for ecosystem functioning has largely been neglected. In this study, we conducted a factorial experiment in which three common plant species were planted in a gradient of species richness (one, two, and three) and seven species compositions at two densities (six and twelve individuals per microcosm). Plant total biomass and total organic carbon (TOC) and total inorganic nitrogen (TIN) removal efficiency were measured to explore the effect of plant species diversity and density on the ecosystem functioning of CWs. Results showed that (1) plant species richness had no significant effect on plant total biomass and TOC and TIN removal efficiency under high and low plant density. (2) There were significant differences in TIN removal efficiency among seven species compositions under low plant density; especially, the presence of Canna indica reduced the TIN removal efficiency. In contrast, species composition and species identity had no significant effect on ecosystem functioning under high plant density. (3) High plant density increased plant total biomass of C. indica monocultures, and also enhanced TIN removal efficiency in mixtures of two species. These results indicated C. indica alone may not be an ideal species for enhancing pollutant removal in constructed wetlands but planting at high density could mitigate its negative effect on ecosystem functioning.

The effectiveness of early generation selection under low and high plant density was evaluated in faba bean (Vicia faba L.). For this, the faba bean cv. 'Polycarpe' was pollinated by eight higher yielding cultivars of different origin. The F1's and F2's together with 'Polycarpe' and the pollinator with the highest yielding ability (cv. 'Effe') were evaluated under high plant density with adjacent controls and under low plant density in a honeycomb design. It was found that the eight hybrids had a different ranking at low than at high plant density for both generations (F1and F2). Hybrid Pol.x A-58 had the best combined yield performance in the F1and F2under high and hybrid Pol.x A-37 under low plant density. Application of individual plant selection in the F2and F3generation of the two crosses (Pol.x A-58 and Pol.x A-37), under both low plant density according to UNR-O honeycomb design and high plant density using a moving average, resulted in the selection of four groups with 20 selected F3plants each. Within each group, equal numbers of seeds from each plant were mixed to establish four mixtures. These mixtures together with two controls ('Polycarpe' and 'Effe') were evaluated in a randomized complete block design (22 plants/m2) in one location for two years. It was found that the material selected continuously under low plant density had a significantly higher yield than the material selected under high plant density. In addition, the material selected from Pol.x A-37 (H1R2) under high plant density had a lower mean yield than that selected continuously under low plant density (H1H2). Their average yield over years was significantly higher than the yield of the material selected from Pol.x A-58 under both plant densities. Furthermore, the material selected from Pol.x A-58 under low plant density, had a significantly higher mean yield over years than its sibs selected under high plant density. It was concluded that honeycomb selection at low plant density can be used effectively for early generation selection in faba bean.

It is generally believed that grain yield per unit area of modern maize hybrids is related to their adaptability to high plant population density. In this study, the effects of two different plant densities (52,500 and 90,000 plants/hm2) on 12 traits associated with yield were evaluated using a set of 231 F2:3 families derived from two elite inbred lines, Zheng58 and Chang7-2. Evaluation of the phenotypes expressed under the two plant density conditions showed that high plant density condition could decrease the value of 10 measured yield component traits, while the final grain yield per hectare and the rate of kernel production were increased. Twenty-seven quantitative trait loci (QTLs) for 10 traits were detected in both high and low plant density conditions; among them, some QTLs were shown to locate in five clusters. Thirty QTLs were only detected under high plant density. These results suggest that some of the yield component traits perhaps were controlled by a common set of genes, and that kernel number per row, ear length, row number per ear, cob diameter, cob weight, and ear diameter may be influenced by additional genetic mechanisms when grown under high plant density. The QTLs identified in this study provide useful information for marker-assisted selection of varieties targeting increased plant density.

Winter cereal production systems in the northern USA are inefficient with respect to the capture of photosynthetically active radiation (PAR) during the year. Our objectives were to determine radiation use efficiency (RUE) in winter wheat (Triticum aestivum L.) and triticale (× Triticosecale Wittmack) at low (67–125 plants m−2), medium (116–170 plants m−2), and high (205–332 plants m−2) plant densities and RUE of interseeded red clover (Trifolium pratense L.) during two growth periods after cereal harvest. During the linear phase of cereal growth (GS 30–80), RUE averaged across plant density was 3.50 g MJ−1 for wheat and 3.21 for triticale in 2004 and 3.37 for wheat in 2006. In 2006, triticale RUE was similar at the low and medium plant density (3.28 g MJ−1) but lower at the high plant density (2.84 g MJ−1). Red clover RUE following wheat and triticale differed by growth period and exhibited varying levels of plant density dependence within growth period. Following wheat at the high plant density, RUE ranged from 1.40 to 1.97 g MJ−1 across years and growth periods. Following cereal harvest in mid‐July until early October, red clover interseeded in wheat intercepted on average 65% (2004) and 35% (2006) of incident PAR. The wheat–red clover system was more robust than triticale–red clover for grain RUE and intercepting PAR after cereal harvest.

The strong association of prolificacy in maize with tolerance to high plant density reported in the literature by many investigators has stimulated us to study the inheritance and expression of such trait under high and low plant densities. A diallel cross among eight diverse inbred lines in number of ears plant -1 was performed in 2010 season and the resulting F1’s along with their parental lines were evaluated in 2011 season under two plant densities (20,000 and 40,000 plants fed -1 ) using a split plot design in randomized complete blocks (RCB) arrangement with three replications at two locations (Bani Sweif and Minufiya). The main objective was to obtain information on the expression of genes controlling maize prolificacy under low and high plant density. Analyses of variance indicated existence of significant differences among locations, plant densities and genotypes for all studied traits. Performance of inbred lines and F1 crosses vary with location and plant density. Parental lines L14, L17, L18 and L53 were the best in mean performance and general combining ability effects (GCA) for ears plant -1 (EPP), grain yield plant -1 (GYPP) and grain yield fed -1 (GYPF) under high and low densities. The best F1 crosses in mean performance and specific combining ability effects (SCA) under high-density were L14×L17, L14×L18 and L18×L20 for EPP and L14×L17, L18×L20 and L18×L55 for EPP and GYPP. Type of dominance controlling inheritance of EPP trait changed from complete dominance to the prolific parent under low density to complete dominance to the non-prolific parent under high density. Results indicated that to obtain a hybrid of high EPP and GYPP under high-density, at least one of its parents should be prolific, but to obtain a hybrid of high GYPF, both of its parents should be prolific. The magnitude of genetic variance (additive and dominance) and heritability in narrow-sense for the three traits EPP, GYPP and GYPF was lower under high-density than that under low-density. Both additive and dominance variances were highly significant for the three traits, but the magnitude of dominance was higher than that of additive variance. Results confirm the simple inheritance of EPP trait (one gene) as reported by some investigators under high and low density. Prolificacy may be rapidly transferred from a prolific exotic inbred to the non-prolific Egyptian inbreds used in commercial hybrids by a conversion backcrossing program. Expected genetic advance (GA) from selection ranged from 9.49% for high EPP to 22.66% for GYPP under highdensity. Estimates of GA were higher under low than under high-density, indicating that selection for high EPP is more efficient than under low-density. Correlation coefficients for means vs. GCA effects of inbreds, means vs. heterobeltiosis, means vs. SCA effects and SCA effects vs. heterobeltiosis of F1 crosses as well as parents means vs. offspring means and breeding values were estimated and discussed.

Effects of deficit irrigation and plant density on the growth, yield and fiber quality of irrigated cotton