Stem Elongation Initiation Research Articles

Relationship between canopy coverage at the initiation of stem elongation and lodging in wheat

While lodging in wheat appears to correlate with the ratio of canopy coverage at the initiation of stem elongation (CC30), a mechanistic understanding of the relationship between lodging index and CC30 is lacking. The objective of this study was to examine more closely the relationship between lodging and CC30 and to identify the most effective sowing densities and/or planting patterns in reducing lodging. The CC30 was adjusted by varying the sowing density and planting pattern, i.e., wide vs narrow-spaced rows and altering the seed spacing within the row and by spread sowing. We found that CC30 was positively correlated with the lodging degree at maturity and was negatively correlated with internode dry weight per unit length. The CC30 for a sowing density of 3 g m−2 (which is about half the conventional sowing density in Japan) was low at a range of 28–75 %. In these treatments, CC30 was lowest under spread sowing where the spacing between plants was greatest. The yield of the 3 g m−2 spread-seed treatments was more than 500 g m−2. This yield is comparable to that of the other treatments even though the sowing density was much lower. The aboveground N accumulation at maturity of the 3 g m−2 spread-seed treatments was similar to that of the other treatments. As found in the spread-seed treatments, our results suggest that lowering CC30 by reducing the sowing density and/or by changing the planting pattern, increased the spacing between seedlings and thus helped to prevent lodging while still retaining high yields.

Hybrids Provide More Options for Fine-Tuning Flowering Time Responses of Winter Barley.

Crop adaptation requires matching resource availability to plant development. Tight coordination of the plant cycle with prevailing environmental conditions is crucial to maximizing yield. It is expected that winters in temperate areas will become warmer, so the vernalization requirements of current cultivars can be desynchronized with the environment’s vernalizing potential. Therefore, current phenological ideotypes may not be optimum for future climatic conditions. Major genes conferring vernalization sensitivity and phenological responses in barley (Hordeum vulgare L.) are known, but some allelic combinations remain insufficiently evaluated. Furthermore, there is a lack of knowledge about flowering time in a hybrid context. To honor the promise of increased yield potentials, hybrid barley phenology must be studied, and the knowledge deployed in new cultivars. A set of three male and two female barley lines, as well as their six F1 hybrids, were studied in growth chambers, subjected to three vernalization treatments: complete (8 weeks), moderate (4 weeks), and low (2 weeks). Development was recorded up to flowering, and expression of major genes was assayed at key stages. We observed a gradation in responses to vernalization, mostly additive, concentrated in the phase until the initiation of stem elongation, and proportional to the allele constitution and dosage present in VRN-H1. These responses were further modulated by the presence of PPD-H2. The duration of the late reproductive phase presented more dominance toward earliness and was affected by the rich variety of alleles at VRN-H3. Our results provide further opportunities for fine-tuning total and phasal growth duration in hybrid barley, beyond what is currently feasible in inbred cultivars.

Transcriptome analysis reveals key genes regulating signaling and metabolic pathways during the growth of moso bamboo (Phyllostachys edulis) shoots.

Moso bamboo (Phyllostachys edulis), a high-value bamboo used to produce food (young shoots), building, and industrial goods. To explore key candidate genes regulating signal transduction and metabolic processes during the initiation of stem elongation in moso bamboo, a transcriptome analysis of the shoots during three successive early elongation stages was performed. From cluster and differential expression analyses, 2984 differentially expressed genes (DEGs) were selected for an enrichment analysis. The DEGs were significantly enriched in the plant hormone signal transduction, sugar and starch metabolism, and energy metabolism pathways. Consequently, the DEG expression patterns of these pathways were analyzed, and the plant endogenous hormone and carbon metabolite (including sucrose, total soluble sugar, and starch) contents for each growth stage, of the shoot, were determined. The cytokinin-signaling pathway was continuously active in the three successive elongation stages, in which several cytokinin-signaling genes played indispensable roles. Additionally, many key DEGs regulating sugar, starch metabolism, and energy conversion, which are actively involved in energy production and substrate synthesis during the continuous growth of the shoots, were found. In summary, our study lays a foundation for understanding the mechanisms of moso bamboo growth and provides useful gene resources for breeding through genetic engineering.

Effect of nitrogen scheduling on nitrogen uptake pattern and seed protein yield, oil yield and oil quality of canola oilseed rape (Brassica napus) sown on different dates

A field experiment was conducted at the Punjab Agricultural University Ludhiana during rabi 2016-17 to study the effect of nitrogen (N) application dose and time on N uptake pattern, protein and oil yield and oil quality ofcanola oilseed rape (Brassica napus) under different sowing dates. The treatments comprised three sowing dates (15 October, 30 October and 15 November) in the main plots and seven combinations of dose (100 and 125 kg/ha) and time of application of N (two or three splits) in sub plots. Loamy sand soil of experimental field was low in organic carbon and available N in the upper 15 cm soil profile. The test variety GSC 7 was sown at spacing of 45 cm x 10-12 cm. Delay in sowing significantly reduced the N content and uptake by canola oilseed rape at all growth stages in different plant parts as well as in seed and stover at maturity except N content in stem at 80 DAS. The highest oil yield (941 kg/ha) obtained with 125 kg/ha of N applied as 50 kg at sowing + 50 kg at initiation of stem elongation + 25 kg at initiation of flowering was at par with application of 125 and 100 kg/ha of N in two equal splits at sowing and initiation ofstemelongation. The highest protein yield (738 kg/ha) obtained with 125 kg/ha of N applied in three splits (50 + 50 + 25) was significantly higher than all other treatments. The highest oil yield produced by 15 October sown crop with application of 125 kg/ha of N in three splits (1056 kg/ha) was 7.3% and 40.4%% higher than application of 100 kg/ha of N in two equal splits and 6.7% and 35.9% higher than 125 kg/ha of N in three splits in 30 October and 15 November sown crop, respectively. Fatty acid composition of oil was not influenced by sowing dates and N scheduling.

Hormone Distribution and Transcriptome Profiles in Bamboo Shoots Provide Insights on Bamboo Stem Emergence and Growth.

Growth and development are tightly co-ordinated events in the lifetime of living organisms. In temperate bamboo plants, spring is the season when environmental conditions are suitable for the emergence of new shoots. Previous studies demonstrated that bamboo plants undergo an energy-consuming 'fast stem growth' phase. However, the events during the initiation of stem elongation in bamboo are poorly understood. To understand the onset of bamboo stem growth, we performed hormone and transcriptome profiling of tissue regions in newly elongating shoots of the Moso bamboo Phyllostachys edulis. The growth hormones auxins, cytokinins and gibberellins accumulated in the shoot apex, while the stress hormones ABA, salicylic acid (SA) and jasmonic acid (JA) are predominantly found in the lower part of the stem. The mature basal part of the stem showed enrichment of transcripts associated with cell wall metabolism and biosynthesis of phenylpropanoid metabolites, such as lignin. In the young upper stem region, expression of cell formation- and DNA synthesis-related genes was enriched. Moreover, the apical region showed enhanced expression of genes involved in meristem maintenance, leaf differentiation and development, abaxial/adaxial polarity and flowering. Our findings integrate the spatial regulation of hormones and transcriptome programs during the initiation of bamboo stem growth.

Responses of plant development, biomass and seed production of direct sown oilseed rape (Brassica napus) to nitrogen application at different stages in Yangtze River Basin

Direct sown oilseed rape has been rapidly developed in recent years due to increasing shortage of labor force in the winter oilseed rape (Brassica napus L.) region of Yangtze River Basin. However, the appropriate nitrogen management of the crop has not yet been established, resulting in poor seed yield. Two experiments were conducted, including a pot trial to elucidate the N utilization in different growth periods under sufficient supplies of N and other nutrients, and a field experiment to study the effects of N application rates at different stages on plant development, biomass production, seed yield and N use efficiency of direct sown oilseed rape. The results showed that N applications at different stages extended the growth period of the crop. The vegetative growth was extended more than the reproductive growth by N applied at early stages. Nitrogen application promoted the plant growth center/s leading to high biomass accumulations in different periods. Higher pre-sowing N rates prolonged the fast biomass accumulation period and increased the fastest accumulation speed. The seed yield and NUE of the crop were improved by N applied prior to sowing and at the initiation of stem elongation. The results suggest that, relatively high N rate but not exceeding 135kgNha−1 applied at pre-sowing, 67.5–90kgNha−1 at the initiation of stem elongation, and appropriate rates depending on the seedling growth at 5-leaf stage were optimum N fertilizer strategies to achieve high production for the direct sown winter oilseed rape in Yangtze River Basin.

Effects of day length, light quality and ethylene on PHYTOCHROME B expression during stem elongation in Stellaria longipes

The prairie ecotype of Stellaria longipes (Caryophyllaceae) is highly responsive to light and is a shade avoider. Using the prairie ecotype as a model, we investigated the expression of the PHYTOCHROME B (PHYB) gene in response to different ratios of red to far-red light (R/FR), photoperiods and ethephon, an ethylene producing compound. This was done to examine the potential role of the PHYB and its interaction with ethylene in determining the plasticity of stem elongation. The PHYB gene was constitutively expressed in flowers, leaves, stems, and roots. The relative transcript abundance of the PHYB gene increased significantly upon transfer of etiolated-seedlings to light. The level of the PHYB gene transcript under elevated R/FR (3.5) was significantly higher than that under lower R/FR (0.7) in de-etiolated-mature plants. Long day photoperiod (16 h light/day, LD) significantly promoted stem growth, whereas plants under short day photoperiod (8 h light/day, SD) showed minor elongation. Interestingly, under LD, but not under SD, the level of PHYB mRNA significantly correlated with stem elongation. The plants treated with high concentration of ethephon (10.0 mol m−3) showed a 55% decrease in PHYB transcript within the first 4 days after treatment, and the level of PHYB transcript was significantly lower than that in control plants and the plants treated with a lower concentration of ethephon (0.1 mol m−3). Taken together with our earlier studies related to stem elongation, our results suggest that the level of PHYB gene transcription on day 4 is critical for the initiation of stem elongation. After this stage, a relatively high level of the PHYB gene transcription might be important for maintaining stem elongation of the prairie plants of S. longipes.

Diallel analysis of vernalisation responses in spring rape (Brassica napus L.): a basis for adaptation to a Mediterranean environment

The capacity for vernalisation varies among genotypes of spring rape, Brassica napus L., and any vernalisation response reduces their suitability for cultivation in the Mediterranean environment of south-western Western Australia. The genetic basis of this variation was studied in the F1 generation of a diallel cross among 5 inbred genotypes derived from a cross between 2 cultivars differing in sensitivity to vernalisation. In non-vernalised plants the number of leaf nodes at flowering, time to flowering, stem height at flowering, and time to initiation of stem elongation showed substantial genetic variation, both additive and dominance effects being significant. The time to initiation of stem elongation was not vernalisation-sensitive, but for the other 3 characters the response to vernalisation showed significant genetic variation, largely additive. The genetic effects controlling the number of leaf nodes at flowering were clearly different from those controlling stem height at flowering, and hence could be manipulated independently by selection. Moreover, the genetic effects controlling these characters in the absence of vernalisation were different from those controlling the response to vernalisation. Discontinuities in the distributions of the parent means and other statistics for the number of leaf nodes at flowering suggested that major Mendelian genes may largely control this character and its response to vernalisation. Comparison of the number of leaf nodes at flowering in the presence and absence of a vernalising stimulus is therefore suggested as a selection criterion for the elimination of vernalisation response. However, in the absence of a vernalising stimulus, the time to flowering will be the character easiest to influence by selection.

Incorporation of Carbon‐14 into the Indigestible Fraction of Timothy Herbage1

A better understanding of the nature of herbage‐quality deterioration of forages as they mature may aid in making crop management and crop improvement decisions. The purpose of this study was to follow the incorporation of carbon‐14 into the indigestible fraction of timothy (Phleum pratense L.) herbage at initiation of stem elongation, ear‐emergence, and anthesis. Plants grown in cans outdoors were exposed to 14C‐labeled CO2 and then harvested at intervals of 1, 3, 8, 32, and 168 hours following initial exposure at each growth stage. Herbage was divided into leaf blades, leaf sheaths, and stems at each sampling time. In vitro dry matter digestibility of each tissue fraction was determined, and the residue from each fraction was analyzed for 14C concentration. Rates of decrease in digestibility were greatest between ear‐emergence and ear‐emergence plus 168 hour growth stages for all tissue fractions. Proportions of whole tissue 14C remaining in the undigested residue of leaf sheaths and stems also were greater at ear‐emergence than at anthesis. Results suggest that rate of incorporation of 14C into indigestible fractions of timothy herbage is greater near ear‐emergence than near initiation of stem elongation or anthesis. Results also suggest that radioisotope studies can be effectively used to obtain a better understanding of plant tissue chronology, cell wall polysaccharide formation, and forage digestibility.

Growth and Development of Polemonium Foliosissimum on High Elevation Rangeland in Utah

Polemonium foliosissimum A. Gray var. alpinum (Brand) is a perennial forb of high elevation aspen and herbland range. In northern Utah, the annual life cycle is completed within approximately 3 months after snowmelt; stem elongation occurs in June, flowering in July, and seed maturation and dispersal in August. A low temperature stratification treatment to the perennial parts was necessary for the initiation of stem elongation, and subsequent long photoperiods were required for continued growth and flowering. Seed germination was restricted by the copious sheath of mucilage that surrounds wetted seeds; this restriction was largely removed by a 15-min acid scarification treatment. Carbohydrate reserves in the caudex generally increased continuously from the flowering through the seed dispersal stages. Clipping treatments applied for 4 consecutive years at three phenological stages reduced subsequent growth and vigor. Recovery from clipping treatments was slow over an additional 3 years. INTRODUCTION Polemonium foliosissimum A. Gray var. alpinum (Brand), white polemonium, is an important perennial forb of high elevation aspen and herbland range, because of its abundance in localized areas and its palatability to livestock and big game. The species occurs in subalpine areas of the Intermountain States from Idaho to New Mexico and in Colorado. Davidson (1950) considered the species to be a complex of intergrading populations. Using morphological, cytological and chromatographic analyses as his basis, Anway (1968) segregated four varieties (alpinum, flavum, foliosissimum and molte) that overlap in many characters and form continuously varying populations for nearly all characters. Plants of the present study generally agreed in morphology with the characters of variety alpinum, which ranges through the mountains of northern Utah, northeastern Nevada and southwestern Wyoming. STUDY SITEES Studies were conducted in aspen and herbland range on the Mud Creek Sheep Allotment (Uinta National Forest) and Tony Grove Canyon (Cache National Forest), both in northern Utah. The environmental conditions and plant community composition are typical of high elevation sites in this region. Mud Creek was described by Matthews and Conrad (1968) and Tony Grove by Florez (1971). Polemonium is widely distributed, but plant densities are generally low in the study areas; cover values ranged from less than 1 % in aspen 1 The authors were stationed at Logan, Utah, at the Forestry Sciences Laboratory, which is maintained in cooperation with Utah State University,

Root and Foliage Growth of Oats at Several Levels of Fertility and Moisture1

AbstractThe effects of fertility and moisture on root and shoot gorwth of oats (Avena sativa L.) were studied in potculture experiments. An experimental unit was a 75‐liter garbage can filled with low‐fertility Thurman sand, embedded 0.6 m deep in the soil. Forty‐eight can were covered with a plastic shelter to permit controlled moisture regimes. A factorial set of fertilizer treatments using two levels each of N (0 and 140 kg/ha), P (0 and kg/ha), and K (0 and 93 kg/ha) were applied at seeding time. At the initiation of stem elongation, wet (field capacity) and dry (wilting coefficient) moisture regimes were imposed across all fertility treatments.Traits measured on the plant tops were plant height, number of tillers, number of spikelets per panicle, dry weight and stem diameter. Weights were taken on roots extracted from 0.007‐m3 soil samples from the 0‐15‐, 15‐30‐, 30‐45‐, and 45‐60‐cm soil depths.The root and shoot growth responded more to fertilizer application when moisture was adequate than when deficient. Nitrogen and phosphorus, applied alone and in combination, gave more shoot and root growth than any other element or combination of elements. Shoot growth responded to added fertilizer in both the high and low moisture regimes, but root growth responded only in the wet regime. Leaching of the nutrients with surface irrigations caused maximum root response to N in the 30‐45‐ cm zone, but for P, which resists leaching, maximum response was in the 0‐15‐cm zone. Reduced root‐top ratios resulting from added moisture and fertilizer elements were due largely to large increases in top growth without concomitant increases in root growth.Increase in shoot weight from added fertilizer under the dry regime was not accompanied by increased root weight. We concluded that root response to added fertility could not be responsible for oat plants utilizing subsoil (30‐60‐cm depth) moisture to produce increased shoot weights.

MORPHOGENETICAL STUDIES IN THE DEVELOPMENT OF SUCCESSIVE LEAVES IN ASTER, WITH RESPECT TO RELATIVE GROWTH, CELLULAR DIFFERENTIATION, AND AUXIN RELATIONSHIPS

IT IS the purpose of this paper to report an investigation of the development of both the rosette and cauline leaves in two inbred species of Aster and in reciprocal hybrids resulting from a cross between these species. Specifically an attempt was made to study the morphological processes by which the ultimate form of the leaf is attained in these plants, particular emphasis being placed on, cell numbers, orderly sequence of cell division, cellular differentiation, and relative growth rates in tlle leaf as a whole and in various reoions of the leaf. Along with these morphogenetical studies, the auxin output of these leaves, as measured bv auxin diffusions, has been determined and its distribution in relation to the pattern of growth in the leaves noted. An analysis of this pattern of growth is attempted in order to determine whether a differential regional distribution of auxin within the leaf might be correlated with differential growth of the leaf. Finally there is reported a study of the developmental pattern for the successive leaves in these plants. The question arises as to whether or not the relationships of length and breadth of leaf are constant throughout the entire life of the plant. This investigation points out that such relationships do change and indicates when and wliere they occur. An explanation of the biological factors underlying such changes, however, is not at all clear. MATERIALS AND METHODS. -Two species of Aster, A. novae-angliae L., A. multiflorus Ait.2 and their reciprocal hybrids were used in these investigations. The developmental studies w ere based on the cotyledons and the first twenty leaves of the seedlings. These were chosen because they afforded the opportunity of studying the relative growth rates of the rosette leaves and of those cauline leaves appearing with and subsequent to the initiation of stem elongation. Leaf studies were also made on the second year's growth as well, again both from the rosette and the elongating axis. The leaves of these plants were chosen becau'se the species had been inbred for two or more generations over a period of three years, during which time the writer has attempted to familiarize himself with their genetical trends, their comparative morphology, and