Subsoil compaction affects all aspects of soil quality which may result reduction of crop development. An experiment was conducted in a phytotron using a randomized block design to evaluate the effects of different levels of subsoil compaction on forage legume crop development and mineral nutrient acquisition and translocation in an Andisol. A clay loam Andisol was used to grow the soybean, chickpea and lentil at different levels of subsoil compaction as no compaction (0 J), medium compaction (500 J) and high compaction (1000 J). Plants were also grown under same condition in surface compaction. In this experiment, the effects of soil compaction on soil physical and hydrological properties as well recorded. The bulk density of soil increased substantially with increasing compaction. Consequently the air-filled porosity and void ratio of soil decreased with increasing compaction. Compacted soil retains more water at higher matric suction. Shoot and root weights of the plants were significantly higher at 0 J than at 500 J compaction levels indicating that soil compaction hampered normal plant growth in Andisol, irrespective of crops. Furthermore, the yields of plants tended to remarkably decrease with increasing of soil compaction from 500 J to 1000 J for both surface and subsoil compaction. Although the reduction of crop yields from 500 J to 1000 J was not always statistically significant. The severity of the detrimental effect of compaction on dry matter production could be presented as chickpea > lentil > soybean. The results obtained in the study revealed that apart from Ca uptake by roots, compaction hampered nutrient assimilation in both shoot and root of all the crops. Similarly, the translocation of nutrients in the shoot of the plants was adversely affected by compaction. This study revealed that the effect of surface soil compaction was less severe on the forage legume crops than subsoil compaction. We confer that the morphological and physiological changes in three legume forages differed in both surface and subsoil compaction.
Oxygen gas is one of the environmental factors closely related to photosynthesis and respiration. In this article, we investigated the effects of long-term exposure to different O2 concentrations on growth and phytochemical contents in leaf lettuce. In order for provide exposure to low O2 for longer periods, we developed a new growth chamber combined with N2 gas generator. Plants were hydroponically cultured under 3, 10 or 21% O2. The leaf area of the plants grown at 3% O2 was significantly smaller than that for plants grown at 21% O2; however, there was no significant difference in dry weight. Owing to this, the specific leaf area of plants grown at 3% O2 was significantly lower than that for plants grown at 21% O2. While the nitrogen content of plants grown at 3% O2 was significantly lower than that for plants grown at 21% O2, the anthocyanin content of plants grown at 3 and 10% O2 was significantly higher than that for plants grown at 21% O2. According to results, we discussed that reduced leaf expansion observed in plants grown at low O2 was the result of the decreased nitrogen.
The phloem exudate prepared from the cotyledons of Ipomoea tricolor strain Heavenly Blue seedlings that have been exposed to a single 16 h dark period induced flowering in cultured apices excised from non-induced seedlings. When the phloem exudate was dialyzed and separated to 3 fractions such as low (‹1,000), middle (1,000–10,000), and high (›10,000) molecular weight, both low and high molecular weight fractions had flower-inducing activities, but not middle fraction. The low molecular weight fraction was further separated and examined the nature of flower-inducing substance(s). The substance(s) was heat-stable and the highest rate of floral bud induction was obtained with 3 μg freeze dry weight mL −1. From the results of solvent participation and ion exchange chromatography, the substance(s) was high polar, seemed to be acidic, and the flower-inducing activity only increased from 3- to 10-fold.
The flower-inhibiting activity of phloem exudate prepared from cotyledons of Ipomoea tricolor strain Heavenly Blue seedlings cultivated to continuous light conditions was examined, using apex cultures in vitro as a bioassay system. The phloem exudate inhibited flowering in apices excised from seedlings exposed to a single 16 h dark period to induce flowering. When the phloem exudate was dialyzed and separated to 3 fractions such as low (‹1,000), middle (1,000–10,000) and high (›10,000) molecular weight, low molecular weight fraction had flower-inhibiting activity, but not middle and high molecular weight fractions. The low molecular weight fraction was separated and examined the nature of the flower-inhibiting substance(s). The flower-inhibiting activity appeared to be heat-stable. The low molecular weight fraction was extracted by CHCl 3 and ethyl acetate. The fraction with activity from solvent participation was further fractionated by ion-exchange chromatography. The active fractions were applied to a Sep-Pak C18 cartridge. From the results of fractionation, the flower-inhibiting substance(s) was low molecular weight, high polar, seemed to be basic, and the flower-inhibiting activity was increased about 10-fold.
The effect of supplemental lighting with high irradiance LED on growth and fruit yield of various cultivars was examined in forcing culture of strawberry. Four cultivars of strawberry plants, having the different flowering timing and the flower number per inflorescence were illuminated 12 h daily from October to May. Supplemental lighting significantly accelerated leaf photosynthesis in all cultivars, which supported the translocation of additional carbohydrate to fruits, and improved fruit quality compared with non-lighting treatments. The flower opening of 2nd inflorescences in ‘Sagahonoka’ and ‘Benihoppe’ were accelerated by supplemental lighting, and this brought a remarkable increase in fruit yield. In ‘Akihime’, flower number per inflorescence was remarkably increased through an acceleration of leaf photosynthesis resulting in a significant increase in fruit yield. In ‘Ookimi’, supplemental lighting inhibited flower bud differentiation, and the positive effect of supplemental lighting was not observed on fruit yield. An acceleration of anthesis and an increase in flower number under supplemental lighting varied in each cultivar. These results suggest that supplemental lighting provided based on the hereditary characteristics (e.g., flowering timing, flower number) of each cultivar is appropriate for high-yield production based on the stabilizing effect of supplemental lighting in forcing culture of strawberry.
Nitrate-N (NO3-N) leaching in intensive crop production systems is an important issue due to its potential as a pollutant and a valuable resource. This study aimed at evaluating NO3-N leaching using on-farm measurements and modeling of 12 commercial fields of leafy vegetables characterized by an array of farm management. Real-time monitoring of the soil moisture, temperature and bulk electrical conductivity using a capacitance/resistance sensor was carried out to verify the temperature index and the leaching constant integrated in the soil nitrogen balance estimation system. Results showed that measured soil temperature strongly correlated to model estimates. Values of the leaching constant were 0.0006 kg kg−1 and 0.00075 kg kg−1 (in 2013) both of which were close to the model value of 0.0007 kg kg−1. Values in 2012 were either too high (0.00127 kg kg−1) or too low (0.0010 kg kg−1). NO3-N leaching ranged from 13.50 kg ha−1 to 72.71 kg ha−1 in 2012 and 8.66 kg ha−1 to 41.10 kg ha−1 or 0.00 kg ha−1 to 41.10 with or without rye, respectively. NO3-N leaching in single cropping systems of 2012 was higher than in double cropping systems of 2013.
We present a detailed study of differences in the fruit ripening stage on the vines and ethylene treatment in the red kiwifruit cultivar ‘Rainbow Red’ (Actinidia chinensis). We evaluated the fruit quality (core and flesh firmness, soluble solid content (SSC), and titratable acid (TA)); ethylene metabolism; and gene expression of ACS1, ACO3, EIL4, ERF14, and PGB at each stage. Fruits on the vines somewhat softened gradually. SSC increased, and core and flesh firmness as well as TA decreased gradually. However, rapid ethylene production was not observed, and gene expression of ACS1, ACO3, EIL4, ERF14, and PGB was at the basal level at each stage. While the fruit quality following ethylene conditioning, core and flesh firmness, and TA rapidly decreased, SSC and ethylene production rapidly increased. It was confirmed that gene expression of ACS1, ACO3, EIL4, ERF14, and PGB rapidly increased. These results suggested that the ripening of ‘Rainbow Red’ on the vines is not associated with ethylene.
Large blooms of Nomura's jellyfish (Nemopilema nomurai Kishinoue) have recently observed in the Japan Sea, and caused serious damage to fisheries. It may be worthwhile to develop beneficial uses the jellyfish. We investigated the growth inhibitory activity of the jellyfish on the growth and emergence of weeds under laboratory and field conditions. Aqueous methanol extracts of the jellyfish inhibited the seedling growth of timothy (Phleum pratense L.), ryegrass (Lolium multiflorum Lam.) and barnyardgrass (Echinochloa crus-galli (L.) Beauv.) in the concentration dependent manner under a laboratory condition. Dried jellyfish incorporated into paddy field also inhibited weed emergence during rice (Oryza sativa cv. Hinohikari) cultivation. Therefore, the jellyfish may potentially be useful as soil additive materials to control weeds in the sustainable agriculture.
Recently, applications of light-emitting diodes (LEDs) for enhancing the efficiency of photosynthesis have attracted the attentions by many researchers and agriculturalists. In the present study, we proposed both empirical (experimental) and simulative evaluations of chlorophyll-targeting monochromic and white fluorescence-type LEDs as the light sources for algal photosynthesis based on the evolution of O2 by Synechocystis sp. PCC6803.
Growth of roots are central to the physiology and ecology of terrestrial higher plants including forest trees and agricultural crops. Ecologists, ecohydrologists, and biogeochemists need detailed insights into belowground properties and processes where plant roots take place, including changes in water, salts, and other elements that can influence ecosystem productivity and functioning. While growth and development of root system are dynamic, its status is hardly understood since roots grow belowground thus invisible with any optical means. In this study, we attempted to apply acoustic means for detection of undersoil tree roots, by developing a novel non-invasive sensing technology for detection of belowground plant tissues based on sound propagation in the soil. Novel instrumental set-up was designed for modulation and demodulation of sound signals passed through soil or sand with and without wood or tree roots. We detected the presence of wooden cut pieces and a living tree root both hidden belowground. This first attempt may induce further studies and developments by scientists and engineers for belowground sensing and imaging techniques as novel ecological research tools.