Allometric relationships of plant organs reflect internal coordination of different aspects of organ development, allowing the linking of plant structural development and underlying physiological processes for the development of functional-structural plant models (FSPMs). This paper aims to (i) explore the allometric relationships between organ morphology and fresh biomass in maize; (ii) develop equations to describe these relationships; and (iii) examine the response of allometric relationships to crop water availability and plant density. Datasets were obtained from field experiments in which three commercial maize cultivars (Pioneer 34N43, Pioneer 31H50 and NongDa 108) were grown under different water regimes and plant densities. Relationships are described between (i) lamina length and biomass for all phytomers by a power function, (ii) lamina maximum width and biomass by a power and a logarithmic function separated at ear position, (iii) sheath length and biomass by power and logarithmic functions separated at eighth sheath position where the sheath length peaked, and (iv) internode length and biomass by two power functions separated at the ear position across water regimes and plant densities. The allometric relationships of organ development were not affected by the mild water stress, but were modified by the increased plant densities. Consequently, the allometric relationships found in this study and their expressions using mathematical equations enable plant morphology to be predicted from physiological output (biomass accumulation), which provides a biologically robust mechanism of realizing functional-structural communication used in FSPMs.
We investigated the involvement of guttation and calcium oxalate crystals in the maintenance of calcium homeostasis in leaf blades and petioles of eddo in hydroponic solution containing calcium at different concentrations. Under scanning electron microscopy, two types of crystals were observed in leaf blades and petioles: raphides (bundles of needle-shaped crystals) and druses (multifaceted conglomerate crystals). The number and size of crystals of leaf blades and petioles in 1 mM calcium treatment (control) were smaller than that in 15 mM calcium treatments and larger than that in 0 mM calcium treatment. Calcium contents of leaf blades, petioles and whole plants increased with the increase of calcium concentration in the treatment solution. In addition, calcium-mapping images demonstrated a positive correlation between the amount of calcium in crystal idioblasts and concentration of calcium in treatment solutions. On the other hand, the weight percentage of calcium per mesophyll cell (spongy cell and palisade cell) of leaf blades and per normal parenchyma cell of petioles was stable irrespective of calcium treatment conditions. These results suggest that calcium accumulates in crystals under calcium-excessive conditions and is released from crystals under calcium-deficient conditions to stabilize calcium levels in leaf tissues other than the idioblasts. A positive correlation was observed between the calcium concentration of guttation fluid (µg mL−1), the total amount of calcium in guttation fluid (µg leaf−1 night−1) and the calcium concentration of treatment solutions. These results suggest that guttation eliminates excess calcium and would be involved in maintaining calcium ion homeostasis in eddo.
This study was conducted to evaluate the role of ethylene in acute ozone (O3: 0, 0.1, and 0.3 cm3 m–3; O0, O0.1 and O0.3, respectively)-induced photosynthetic inhibition of paddy rice leaves grown under different atmospheric carbon dioxide concentrations (CO2: 400 and 800 cm3 m–3; C400 and C800, respectively). Ethephon and silver thiosulfate complex (STS) were applied one day before exposure to O3. Gas exchange, chlorophyll fluorescence, and ascorbic acid were measured immediately before (BE), immediately after (AE-0), and 1 d and 3 d after (AE-1, AE-3) the start of the exposure to O3. In the plants exposed to O3, visible leaf symptoms on the adaxial leaf surface appeared at AE-3. O3 decreased photosynthesis-related parameters, total ascorbic acid content, and redox state of ascorbic acid (RDS), and C800 ameliorated O3-induced damage. STS ameliorated the O3-induced visible leaf symptoms and O3-inhibition of photosynthesis but ethephon worsened slightly or did not affect them. Additionally, we evaluated the effects of O3 and CO2 on ethylene production in rice leaves. Although elevated CO2 did not affect ethylene production, exposure to O3 greatly increased ethylene production at AE-0 and rapidly reduced it at AE-1. These results indicate that ethylene is an important component of signal transduction for the extension of O3 injury in paddy rice.
Pigmented rice is receiving much attention due to the large amounts of bioactive compounds and various health benefits. However, little information is available on its agronomic and physiological aspects. This research aimed to explore the effects of salinity on yield and grain quality of pigmented rice and the modulation of salinity responses by exogenous application of spermidine (Spd). Four cultivars of rice were grown in pots until the early booting stage. Thereafter, the plants were sprayed with 1 mM Spd for 7 successive days before being irrigated with 25 mM NaCl instead of tap water until maturity. Grain yield, yield components and harvest index in all rice cultivars were negatively affected by this salinity stress. Pretreatment with Spd dramatically improved yield and yield components of salt-treated plants, particularly the salt-sensitive cultivar. The major yield components which were improved and contributed most to the dramatic increase in seed yield were the number of filled grains per panicle and panicle fertility. Moreover, Spd pretreatment resulted in an increase in K+/Na+ ratio in rice grains. Salt stress increased nutritional quality of mature grains, i.e., total phenolic content, anthocyanins, proanthocyanins and antioxidant activities (evaluated by FRAP, DPPH and ABTS assays) in all rice cultivars. Furthermore, all aspects of health-promoting nutritional characters were further enhanced by Spd pretreatment. Thus foliar spraying of Spd to rice plants prior to salt application improved grain yield as well as nutritional quality of colored rice grains in relation to total phenolics, flavonoid pigments and antioxidant capacities.
A key barrier to widespread use of warm-season grasses in the transition zone between the temperate and subtropical climates is represented by the winter dormancy, a temporary suspension of visible growth of any plant structure including the meristem. In this environment, species with different photosynthetic carbon cycle coexist, leading to asynchrony in growth among warm- and cool-season grasses. The objectives of the present study were (i) to assess the carbohydrate content in four representative zoysiagrasses Zoysia japonica ‘El Toro’, ‘Meyer’, Z. pacifica, and Z. matrella ‘Zeon’ during three successive phases of vegetation phenology, senescence, dormancy, and green-up, and (ii) to characterize the metabolic responses to phenological variations under natural acclimation. Japanese lawn grass genotypes ‘El Toro’ and ‘Meyer’ showed longer dormancy periods than fine-leaved Z. pacifica and ‘Zeon’. In Japanese lawn grass genotypes, the progressive decline of photosynthetic pigments was similar to that observed in the color retention. Over the experimental period, a significantly greater amount of starch reserves was observed in sprigs (horizontal stems) in the Japanese lawn grasses than in the fine-leaved zoysiagrasses. In general, total soluble sugars (TSS) in leaves and sprigs did not show evidence of sugar starvation during the senescence phase. TSS increased significantly during cold acclimation, resulting in a higher metabolic activity at the onset of green-up to support spring regreening in all zoysiagrasses except ‘Meyer’ leaves.
Drought stress is a severe threat to high altitude hulless barley production, which causes oxidative damage, disturbs water relations and photosynthesis, while exogenously applied nitric oxide (NO) has the potential to alleviate these effects. In the present study, the role of NO in improving drought tolerance of hulless barley was evaluated. At the three leaf stage, sodium nitroprusside (SNP), a NO donor, was applied at 50, 100 and 150 μmol l–1 under drought stress, the controls, were kept at full field water capacity without NO treatment. The results showed that drought stress seriously reduced the hulless barley growth and physiological attributes, but NO application alleviated the stress effects. Drought tolerance in hulless barley was strongly related to the maintenance of water content and enhanced capacity of antioxidants, improved stability of cellular membranes and enhanced photosynthetic capacity, plausibly by signaling action of NO. Among the NO treatments, 100 µmol l–1 SNP was the most effective.
Near-isogenic lines (NILs), carrying different combinations of Ppd-1 genes in the genetic background of an early-maturity cultivar Abukumawase were grown at two sites for two years to elucidate the effects of photoperiodic response genes on the growth and yield of early-maturity wheat (Triticum aestivum L.) in central and southwestern Japan. Photoperiod-insensitive genes, Ppd-B1a and Ppd-D1a, accelerated young spike development, and this effect was predominant with Ppd-B1 with no additive effect among them. Ppd-B1a and Ppd-D1a also advanced the jointing stage, heading, and maturity, and the effect of Ppd-B1a on the jointing stage and heading was stronger than that of Ppd-D1a. An additive effect of two genes was detected for heading. Besides, Ppd-B1a and Ppd-D1a reduced culm length and grain weight, although the reduction effect on grain weight was not significant. Meanwhile, the mean temperature from double ridge formation stage to heading was lower in NILs with photoperiod-insensitive genes than in NILs with photoperiod-sensitive gene, and there was a significant correlation between mean temperature from double ridge formation stage to terminal spikelet formation stage and spikelet number per spike as well as between mean temperature from terminal spikelet formation stage to heading and grain number per spikelet. Therefore in a genetic background of extremely early-maturity line of spring type wheat, photoperiod-insensitive genes accelerated wheat growth and reduced spikelet numbers in central and southwestern Japan, and the effect of Ppd-B1a was stronger than that of Ppd-D1a.
Forming a method of judging the degree of soybean vining in the intercropping system is very important for estimating the shade tolerance of soybean germplasm and choosing the special soybean varieties for intercropping system. Thirty varieties were subjected to two treatments (sole and maize-soybean relay strip intercropping system) with three replications in a complete randomized block design. Light environment characteristics in two cropping systems were measured. At the beginning of the bloom stage of soybean when maize was mature, the soybean stem morphology characteristics stem length, node number, hypocotyl length, internode length, stem diameter, stem breaking strength and stem biomass were measured. The results revealed that the intercropped soybean could capture 13.8% photosynthetic active radiation at the vegetative stage, as compared with the sole crop soybean, with longer soybean main stem, internode and hypocotyl, and lower stem diameter at this stage. The relative value of agronomic traits in the sole and intercropping system could be used to calculate the vining severity index (VI) and the weighted vining index (WVI), and the latter could be used as the comprehensive index of the degree of soybean vining in the relay strip intercropping system. Based on the values of WVI, through the Hierarchical Cluster Analysis, the soybean varieties were divided into the 5 clusters, normal, mild, moderate, severe and extreme vining. Eight of the 30 varieties of soybean were normal vining grade and could be used as the parent plants to breed special varieties for intercropping.
Conservation tillage techniques offer considerably reduced soil erosion and improved soil structure but they are rarely used in organic farming systems due to the potentially increased weed pressure. For the use in the transition period to conservation tillage in organic farming, this study investigated the dry matter production, weed suppression and grain yield of winter and spring faba bean (Vicia faba L.), field pea (Pisum sativum L.) and spring narrow-leafed lupin (Lupinus angustifolius L.), monocropped and intercropped with winter wheat (Triticum aestivum L.; winter crops) and oats (Avena sativa L.; spring crops). The different species were grown in no-tillage, reduced tillage and plough tillage systems at three sites in south-eastern Germany. In the no-tillage system the winter field pea grain yields of up to 3.39 Mg ha–1 were similar to the plough tillage system. For spring faba bean and field pea the yield in the reduced tillage system amounted to 2.92 and 3.29 Mg ha–1, respectively which was similar to the plough tillage system, but exceeded not 2.15 Mg ha–1 in the no-tillage system. Narrow-leafed lupin displayed consistently yields below 0.65 Mg ha–1 in the no-tillage system. Normal leafed winter field pea appeared best suited for the transition period to an organic no-tillage system due to the autumn seeding and its high competitive ability. Spring faba bean and field pea can be grown successfully in the reduced tillage system. Intercropping can increase the total grain yield and weed competition as long as sufficient soil nitrogen resources are plant available.
Severe barrenness of maize (Zea mays L.) occurred in 2003 in eastern Hokkaido (Konsen region), one of the coldest areas in Japan. In many fields, tassels with few or no spikelets were observed in the cultivar widely grown in this region. The anthesis date was delayed 7 days from the silking date in the cultivar in the field at Konsen Agricultural Experiment Station (KAES). In July, when the tassels were developing at the 6- to the 9-leaf stage, the air temperature and sunshine hours were much lower in 2003 than in the average year. Therefore, we hypothesized that the barrenness resulted from these specific climatic conditions in 2003. To examine this assumption, we applied low temperature treatment (10ºC for 7 days) to the plants of the cultivar widely grown in this region in 2003 at around the 6- to 9-leaf stage in a greenhouse at KAES. Tassels were formed at the 7-leaf stage, and developed but they did not reach their full-size at the 8-leaf stage. The tassel length was shorter when the plants were subjected to the low temperature treatment, especially at the 8-leaf stage. The days from silking to anthesis was increased by the treatment in 2 of the 3 test years. The present results suggest that the cultivar is sensitive to the low air temperature at the 8-leaf stage for the development of tassels and may result in barrenness.
The production of cellulosic bioethanol from non-edible plants is receiving increasing attention for its potential to avoid food–fuel competition. However, seasonal variability in feedstock supplies increases the costs of stockpiling and limits commercialization. The cellulosic energy plant Napier grass (Pennisetum purpureum) has conventionally been harvested three times per year (on a 4-month cycle) in Indonesia. To shorten this cycle, we examined an alternative system in which every four rows (rather than the entire crop) were alternately harvested every 2 months (partial harvesting). Results from a 20-month experiment indicated that partial harvesting was effective in shortening the supply cycle from 4 to 2 months. Moreover, partial harvesting significantly increased biomass yield, probably as a result of the border effect. Investigations into available light, atmospheric CO2 concentration, and soil volumetric water content suggested that partial harvesting allowed Napier grass to capture more light for biomass production.
To compare the effect of fertilizer nitrogen (N) and fixed N on water use efficiency (WUE), we measured the cumulative evapotranspiration (∑ET) and total dry matter mass (DM) of genge growing in plant growth chambers. When regulating NH4–N application at 11 levels ranging from 0 – 315 mgN flask−1, N concentration of the genge rose from 0.7% to 3.9% as fertilizer N application was increased. Although both DM and ∑ET changed on a quadratic curve, their relationship approximated a single regression line, regardless of N concentration. The effects of rhizobial inoculation of genge samples along with NH4–N application rates of 0, 10.5, 105, and 252 mgN flask−1 were also tested. The samples with application rates of 0 and 10.5 mgN flask-1, where both nodulation and fixed N application were confirmed, had lower WUE than un-inoculated samples. These results suggest that the impact on WUE is much greater in fixed N than in fertilizer N.
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