Heterosis-related genes under different planting densities in maize

Heterosis and increasing planting density have contributed to improving maize grain yield (GY) for several decades. As planting densities increase, the GY per plot also increases whereas the contribution of heterosis to GY decreases. There are trade-offs between heterosis and planting density, and the transcriptional characterization of heterosis may explain the mechanism involved. In this study, 48 transcriptome libraries were sequenced from four inbred Chinese maize lines and their F1 hybrids. They were planted at densities of 45,000 plants/ha and 67,500 plants/ha. Maternal-effect differentially expressed genes (DEGs) played important roles in processes related to photosynthesis and carbohydrate biosynthesis and metabolism. Paternal-effect DEGs participated in abiotic/biotic stress response and plant hormone production under high planting density. Weighted gene co-expression network analysis revealed that high planting-density induced heterosis-related genes regulating abiotic/biotic stress response, plant hormone biosynthesis, and ubiquitin-mediated proteolysis but repressed other genes regulating energy formation. Under high planting density, maternal genes were mainly enriched in the photosynthesis reaction center, while paternal genes were mostly concentrated in the peripheral antenna system. Four important genes were identified in maize heterosis and high planting density, all with functions in photosynthesis, starch biosynthesis, auxin metabolism, gene silencing, and RNA interference

Influence of Planting Density on Diameter and Height in East Texas Pine Plantations

The response of diameter and height of unthinned planted stands ofloblolly (Pinus taeda L.) and slash (Pinus elliottii Eng elm.)pine in East Texas to different classes of planting densities were analyzed. After tracking the development ofdiameterand heightfor 15yron a setofpennanentplots representing a broad range of plantation parameters, average diameter and average height trends were observed. For both species, average diameter values were significantly larger with lower planting densities. 1n contrast, average height growth is insensitive to planting density at younger age classes for loblolly and at older age classes for slash pine plantations

Corn yield response to crowding stress and cropping season

Corn (Zea mays L.) is planted in two seasons per year in northern Iran (mid-April as a main crop and mid-June as a second crop). The main objective of this study was to determine whether corn yield response would differ between these two seasons and different plant populations. Two field experiments were conducted at the Agricultural Research Center of Golestan - Iran in 2007 and 2008 at different planting densities. The results showed that the values of grain yield and most traits were significantly lower in the second season. Maximum grain yield was observed at planting densities of 6.5 plants m -2 in the first season, whereas in the second season grain yield was the same for planting densities between 2.5 and 12.5 plants m -2. Based on the second-year experimental results, the following functions were fitted to show the relationship between yield ha -1 (Y) and planting densities (X) for the first and second seasons, respectively: (Y = -167.6X 2 + 2672.2X + 511.77; R 2 = 0.992) and (Y = 1200.1 ln(X) + 2924.4; R 2 = 0.935). This study found that the optimum plant population was 6.5 plants m -2 under low heat stress, and should be reduced to 2.5-4.5 plants m -2 under heat stress conditions

Respons Pertumbuhan dan Produksi Ketimun (Cucumis Sativus L) terhadap Sistem Pengolahan Tanah dan Jarak Tanam

Cucumber is consumed regularly by inhabitants of Buru District of the Maluku Province, and, its productivity needs to be optimized. Soil tillage and plant density in cucumber cultivation have Influences on competition for nutrient intake, water and light and hence affect plant yield. The aim of this field experiment was to study growth and yield responses of cucumber (Cucumis sativus L.) on different soil tillage systems and planting densities. The field experiment was arranged in a factorial Randomized Block Design to examine several tillage methods (one and two) and planting densities (25 x 25 cm, 40 x 40 cm and 45 x 55 cm). The experimental results showed that there was no effect of interaction between soil tillage and planting density on all variable observed. Single and double tillage methods increased fruit number, fruit diameter, fruit length, fruit weight and root length of cucumber, while planting density gave no effect on all variables measured. Therefore, either single or double tillages and any planting densities tested in this experiment could be recommended in cucumber cultivation in Buru District of Maluku Province

Research on the evolution of main yield components of maize hybrids grown in different climatic conditions on luvosoil from Simnic area

Environmental factors strongly influence the yields of cultivated crops. In maize,drought is one of the major factors limiting biomass and seed production. Five maize hybrids sowed in three different planting densities have been evaluated for their response to water stress conditions comparatively with well-watered conditions. Several yield components were measured: grain yield, ears/plant, ear weight, thousand kernel weight.Under water stress conditions it terms of planting densities grain yield, ears/plant, relative yield weren’t significantly affected, while ear weight and thousand kernels weight were significantly lower for 50000 pl/ha and 60000 pl/ha comparatively with the control. Relative yield was a stable character with mean values close to one planting density to another.Among all studied characters under normal water conditions only grain yield, ears number/plant and thousand kernels weight were significantly affected by planting density

Impact of planting density and organic fertilization on the cultivation of the Greek endemic Helichrysum amorginum Boiss. and Orph.

Native phytogenetic resources can offer valuable germplasm diversity with potential for sustainable utilization. Helichrysum amorginum Boiss. and Orph. (Asteraceae) a Greek endemic, range-restricted neglected and underutilized plant species (NUP) holds significant utilization potential stemming from its known biochemical properties. The current study presents the results of a three-year experimental cultivation scheme of documented Greek H. amorginum germplasm aiming at its sustainable exploitation. Different planting densities in combination with ascending levels of organic fertilization in two distinct experimental fields were applied and plant growth coupled with inflorescence emergence and biomass yield were evaluated across a period of three years. The results highlighted the growth enhancing effect of organic fertilization under different planting densities with lower densities presenting a trend to sustain larger plants in terms of increased plant base diameter. Inflorescence emergence increased significantly from the second cultivation year onwards in both experimental fields with increasing levels of organic fertilization delivering higher rates of inflorescence number under decreasing planting densities. The current study provides a basis for a systematized research scheme that can facilitate further domestication and upscaling efforts leading to the sustainable utilization of H. amorginum in the pharmaceutical and cosmetics sectors, offering at the same time, local economic development