Effects of plant growth regulators on secondary wall thickening of cotton fibres

The effect of plant growth regulators on the secondary wall thickeningof cotton fibre was studied. The results indicated that the GA_S andiP+iPA levels in the fibre of field-grown cotton plantsremained almost constant but the IAA and ABA levels changed considerably duringfibre development. Although the change in both IAA and ABA levels seemed not tobe closely related with the rate of cellulose accumulation, there was still arelationship between the ratio of ABA to IAA and secondary wall thickening. Inin vitro studies, ABA (50mol·L^–1) markedly enhanced theaccumulation of dry matter and cellulose in the fibre cell wall duringsecondarywall thickening, but no similar effect was observed with NAA, GA₃ orkinetin treatments. The role of ABA in secondary wall thickening of cottonfibreis discussed.     

GbEXPATR,a species‐specific expansin,enhances cotton fibre elongation through cell wall restructuring

Cotton provides us the most important natural fibre. High fibre quality is the major goal of cotton breeding, and introducing genes conferring longer, finer and stronger fibre from Gossypium barbadense to Gossypium hirsutum is an important breeding strategy. We previously analysed the G. barbadense fibre development mechanism by gene expression profiling and found two homoeologous fibre‐specific α‐expansins from G. barbadense, GbEXPA2 and GbEXPATR. GbEXPA2 (from the D_T genome) is a classical α‐expansin, while its homoeolog, GbEXPATR (A_T genome), encodes a truncated protein lacking the normal C‐terminal polysaccharide‐binding domain of other α‐expansins and is specifically expressed in G. barbadense. Silencing EXPA in G. hirsutum induced shorter fibres with thicker cell walls. GbEXPA2 overexpression in G. hirsutum had no effect on mature fibre length, but produced fibres with a slightly thicker wall and increased crystalline cellulose content. Interestingly, GbEXPATR overexpression resulted in longer, finer and stronger fibres coupled with significantly thinner cell walls. The longer and thinner fibre was associated with lower expression of a number of secondary wall‐associated genes, especially chitinase‐like genes, and walls with lower cellulose levels but higher noncellulosic polysaccharides which advocated that a delay in the transition to secondary wall synthesis might be responsible for better fibre. In conclusion, we propose that α‐expansins play a critical role in fibre development by loosening the cell wall; furthermore, a truncated form, GbEXPATR, has a more dramatic effect through reorganizing secondary wall synthesis and metabolism and should be a candidate gene for developing G. hirsutum cultivars with superior fibre quality.     

The Influence of Cellulose Content on Tensile Strength in Tree Roots

Root tensile strength is an important factor to consider when choosing suitable species for reinforcing soil on unstable slopes. Tensile strength has been found to increase with decreasing root diameter, however, it is not known how this phenomenon occurs. We carried out tensile tests on roots 0.2–12.0 mm in diameter of three conifer and two broadleaf species, in order to determine the relationship between tensile strength and diameter. Two species, Pinus pinaster Ait. and Castanea sativa Mill., were then chosen for a quantitative analysis of root cellulose content. Cellulose is responsible for tensile strength in wood due to its microfibrillar structure. Results showed that in all species, a significant power relationship existed between tensile strength and root diameter, with a sharp increase of tensile strength in roots with a diameter <0.9 mm. In roots >1.0 mm, Fagus sylvatica L. was the most resistant to failure, followed by Picea abies L. and C. sativa., P. pinaster and Pinus nigra Arnold roots were the least resistant in tension for the same diameter class. Extremely high values of strength (132–201 MPa) were found in P. abies, C. sativa and P. pinaster, for the smallest roots (0.4 mm in diameter). The power relationship between tensile strength and root diameter cannot only be explained by a scaling effect typical of that found in fracture mechanics. Therefore, this relationship could be due to changes in cellulose content as the percentage of cellulose was also observed to increase with decreasing root diameter and increasing tensile strength in both P. pinaster and C. sativa.     

Genotypic differences in some physiological characteristics during cotton fiber thickening and its influence on fiber strength

Cotton (Gossypium L.) fiber strength is linked with many complex physiological and biochemical processes in the stage of secondary fiber cell wall thickening. With the aim of further exploiting of the relationship between fiber strength and genotypic differences in physiological characteristics, the experiment was implemented in Nanjing, China (in the lower reach of Yangtze River Valley in China) at the stage of cotton fiber thickening stage in 2004–2005. The result showed that the higher strength fiber (genotype Kemian 1) always had higher activities of sucrose synthetase (SuSy) and β-1,3-glucan synthase, and more sucrose and callose existed and transformed for cellulose synthesis than these of the other genotypes during the fiber secondary wall thickening period These resulted in a longer and more gently cellulose accumulation and wider range and longer period of fiber strength enhancing. Interestingly, the opposite effects were observed in lower strength fiber of Dexiamian 1 and intermediary indices were found in NuCOTN 33B with middle strength fiber. Taken together, above results suggested the variations in the transformation of sucrose and callose contents, and the dynamics of sucrose synthase and β-1,3-glucan synthase activities, might be one of the physiological reasons causing the differences in the speed of cellulose accumulation and fiber strength formation. Additionally, other results showed: (1) the occurrence of callose content peak might be an important sign of the onset of the secondary wall thickening in the fiber cell; (2) the duration and the maximum growth rate of cellulose rapid accumulation contribute more to fiber strength development than other indices of cellulose rapid accumulation.     

Dynamics of Carbon Accumulation During the Fast Growth Period of Bamboo Plant

Moso bamboo (Phyllostachys pubescens) has an extremely fast growth rate, however little information is available on the dynamics of carbon accumulation during the fast growth period. Bamboo trunk were sampled at three different stages (1: shoot emergence to first shell detachment; 2: first shell detachment to branch emergence; 3: branch emergence to detachment of all shells) and divided into three parts (upper, middle and lower). The average shoot elongation rate and biomass accumulation rate were 17 cm/d and 96 g/d, respectively. The carbon content increased progressively at the growth stage, and the fixed carbon was partitioned into cell wall hemicellulose and cellulose to meet the demand of rapid cell elongation. Different rates of N, P, K, Ca, and Mg content were found among different parts. These results indicated that the fast growth of the bamboo trunk is related to the extraordinary ability of bamboo to assimilate carbon, but not consistently related to mineral nutrients absorption.     

Standardized sampling plan for Aphis gossypii based on the cotton cultivar,plant phenology and crop size

A standardized sampling plan is the starting point for developing a decision‐making system for pest control. Aphis gossypii (Hemiptera: Aphididae) is a destructive sap‐feeding pest on cotton worldwide. However, research addressing cotton cultivar, plant phenology and field size with the aim of developing a sampling plan for A. gossypii has not been done. Therefore, in this study, we developed a standardized sampling for A. gossypii as a function of these factors. To accomplish this, A. gossypii densities in four experimental cotton cultivars were sampled weekly during year one to determine the ideal aphid characteristic to sample (by individual or colony). During year one and two, A. gossypii densities were sampled weekly in the same cultivars to determine sampling unit, sampling technique and the number of samples for an A. gossypii sampling plan. Using the sample number determined, the sampling time was recorded for cotton field size of 1, 5, 10, 50, 100 and 150 ha in order to estimate the sampling cost. In cotton, the count of individuals was the best characteristic for the assessment of A. gossypii. Leaves of the most apical branches for the vegetative and reproductive cotton plant stage were the best sampling units. The best sampling technique was direct counting. The cotton cultivar did not affect the development of the sampling plan. The A. gossypii sampling plan involved the evaluation of 58 samples per zone and required 20 min (<0.35 min/sample) for the evaluation of these samples. However, the walking time between samples was the main factor responsible for the total sampling time and cost in cotton fields, and this factor strongly depends on the size of the cotton field.     

In vitro induction of mutation in cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) and isolation of mutants with improved yield and fiber characters

This paper describes a protocol to develop cotton mutant lines with improved yield and fiber characters. Immature ovules [(15-day post-anthesis ovules (dap)] were irradiated with 10–50 Gy gamma rays and treated with 1–5 mM EMS and SA to investigate the stimulatory effects of mutagenic treatments. During the subsequent field trials, the mutant lines showed significant variations from control lines. Lower dose/concentration of mutagenic treatments effectively stimulate the agronomical characters like early flowering, plant height, number of bolls, yield of seed cotton, ginning percent, seed index, harvest index and fiber characters while exposure at higher dose/concentration results in lowering the value of the parameters. Consequently, we use this approach to induce genetic variability for obtaining novel mutant cotton cultivars. Among the 19 different mutant lines isolated from the study, M7 showed higher morphological variations in terms of yield characters such as plant height, number of bolls, yield of seed cotton, ginning percent and fiber characters. Significant increase in cellulose content was also noted in mutant lines, whereas moderate increase was observed in total fiber units of the mutant lines. The selected cotton mutant lines for cultivars were investigated systematically; these lines significantly increased the potential for agronomical enhancement of cotton yield.     

The effect of stage of maturity on yield and quality of maize grain and stover

Stage of maturity at the time of harvest is considered as one of the factors influencing the nutritive value of crop residues. Thus this study was carried out to assess the effect of harvesting maize at different stages of grain maturity on yield and quality of maize grain and stover. The maize crop was harvested at grain moisture content of 28–30, 20–23 and 10–12%, which were designated as Stages I, II and III, respectively. Grain yield, standardised to 12.5% moisture content, showed an increasing trend, whereas cob, stover, total crop residue and total biomass dry matter (DM) yield showed a decreasing trend with increasing stage of maturity (p>0.05). The declining trend in stover yield with increased stage of maturity was due mainly to leaf loss. There was a significant decrease (p<0.05) in crop residue–grain ratio and leaf–stem ratio and a significant increase in the harvest index and hectolitre weight of the grain as the grain moisture content decreased from about 30 to 10%. Maize stover harvested at Stage I had significantly higher (p<0.05) ash content than those harvested at Stages II and III. The crude protein (CP) content was significantly lower, whereas the neutral detergent fibre and cellulose contents were higher (p<0.05) in Stage III than in Stages I and II. There was a decreasing trend in in sacco DM degradability with increasing stage of maturity. The washing loss, potential degradability and effective DM degradability at 0.03 h⁻¹ rumen outflow rate were higher (p<0.05) in Stage I than in Stages II and III. The volume of gas produced after 3, 6, 12, 24, 48 and 72 h of incubation was higher (p<0.05) in Stage I than in Stages II and III. The a value (the intercept of the gas production curve) and the gas production potential (a+b) were higher (p<0.05) in Stage I than in Stage III. Reduction in the nutritive value of stover with increasing stage of maturity was characterised by reduction in CP contents and increasing concentration of fibrous constituents. These were reflections of changes in the morphological composition of stover and losses of nutrients within the morphological fractions with increasing stage of maturity.     

Differential interactions among cotton genotypes and isolates of Fusarium oxysporum f. sp. vasinfectum

Abstract

The pathogenicity of nine isolates of Fusarium oxysporum f. sp. vasinfectum (Fov) was evaluated on seedlings of 30 cotton (Gossypium barbadense L.) genotypes in 2005 and 2006. Isolate×genotype interaction was a highly significant (P < 0.01) source of variation in wilt incidence, suggesting that physiologic specialization exists within Fov isolates. Cluster analysis of aggressiveness of isolates and susceptibility of genotypes by the unweighted pair-group method based on arithmetic means (UPGMA) placed the isolates and the genotypes in several groups. Isolates were separated into two distinct groups. One group was closely related to race 5 while the other group was closely related to race 1. Cluster analysis also demonstrated that the Egyptian commercial cultivars had unique susceptibility patterns to Fov isolates remotely related to those of the other genotypes. The interaction between experiments of 2005 and 2006 was mainly due to a differential effect of years on the disease incidence for cotton cultivars.     

Cytochemical localization and function of the 3-linked glucan callose in the developing cotton fibre cell wall

Summary Several recent biochemical studies concerning the hemicellulosic content of the developing cotton fibre wall have pointed to an important increase of 1,3-linked glucans at the onset of the secondary wall formation and their slow decrease until the end of fibre development (Meinert andDelmer 1977,Huwyler et al. 1978, 1979,Maltby et al. 1979). These almost insoluble glucans are extra-cellular and possibly associated with the S₁ or winding layer, but no other data on their exact localization were given.By means of a specific fluorescence method, using a 0.05% decolourized aniline blue solution, we show that one of these 3-linked glucans,callose, is always localized, independently of the fibre age, in the innermost wall layer bordering the cell lumen, from the onset of the secondary thickening up to the end of fibre development. Some possible roles assumed by these callose deposits are suggested and discussed. They may be involved in the normal mechanism of cellulose biosynthesis, as being effectively consumed by turnover or, more probably, as forming a permanently restored interface or matrix where cellulose microfibrils undergo a sort of maturation and are oriented before their definitive incorporation in the organized cell wall. They are not to be confused with the wound callose deposits which characterize damaged or immature fibres.     

Effect of Late Planting and Shading on Cellulose Synthesis during Cotton Fiber Secondary Wall Development

Cotton-rapeseed or cotton-wheat double cropping systems are popular in the Yangtze River Valley and Yellow River Valley of China. Due to the competition of temperature and light resources during the growing season of double cropping system, cotton is generally late-germinating and late-maturing and has to suffer from the coupling of declining temperature and low light especially in the late growth stage. In this study, late planting (LP) and shading were used to fit the coupling stress, and the coupling effect on fiber cellulose synthesis was investigated. Two cotton (Gossypium hirsutum L.) cultivars were grown in the field in 2010 and 2011 at three planting dates (25 April, 25 May and 10 June) each with three shading levels (normal light, declined 20% and 40% PAR). Mean daily minimum temperature was the primary environmental factor affected by LP. The coupling of LP and shading (decreased cellulose content by 7.8%–25.5%) produced more severe impacts on cellulose synthesis than either stress alone, and the effect of LP (decreased cellulose content by 6.7%–20.9%) was greater than shading (decreased cellulose content by 0.7%–5.6%). The coupling of LP and shading hindered the flux from sucrose to cellulose by affecting the activities of related cellulose synthesis enzymes. Fiber cellulose synthase genes expression were delayed under not only LP but shading, and the coupling of LP and shading markedly postponed and even restrained its expression. The decline of sucrose-phosphate synthase activity and its peak delay may cause cellulose synthesis being more sensitive to the coupling stress during the later stage of fiber secondary wall development (38–45 days post-anthesis). The sensitive difference of cellulose synthesis between two cultivars in response to the coupling of LP and shading may be mainly determined by the sensitiveness of invertase, sucrose-phosphate synthase and cellulose synthase.     

Effects of ozone fumigation on cotton (Gossypium hirsutum L.) morphology,anatomy, physiology,yield and qualitative characteristics of fibers

This experiment was conducted to study the effect of high ozone concentrations on two cotton (Gossypium hirsutum L.) cultivars. Two cotton cultivars (Romanos and Allegria) were exposed to control (CF < 4 ppb O₃) and 100 ppb O₃. Plant exposure to ozone began eight days after emergence and was interrupted one day before removing the leaves, to calculate the leaf area. Plants were exposed to ozone 7 h/day, in closed and controlled-environment chambers, during their illumination with artificial visible light.In comparison to control plants, plants exposed to O₃ showed chlorotic and necrotic patches on their leaves, increased stomatal or epidermal cell density and yellowness of cotton fibers. Elevated ozone concentration did not have a significant effect on stomatal width, total leaf thickness and thickness of histological components of leaves. Exposure to ozone concentration reduced non-glandular hair density of main leaf veins, plant height, mainstem internode length, chlorophyll content, net photosynthetic rate, stomatal conductance and length and area of bracts and petals. Elevated ozone treatment reduced the maximum length of staminal tube, anther number, pollen grain germination, leaf area, leaf dry weight, boll number, raw cotton weight, total branch length, dry weight of the mainstem–branches–bracts–carpophylls and of root dry weight. Furthermore, exposure to O₃ reduced the seed weight, the lint weight, the yield, the ratio of lint weight to seed weight, the fiber strength, the micronaire, the maturity index and the fiber uniformity index values. This study shows that the exposure to high ozone concentrations mainly affected the rate of photosynthesis, raw cotton weight and strength of cotton fibers.     

In vitro and in vivo evaluation of the prebiotic activity of water-soluble blueberry extracts

The prebiotic effects of water extracts of two blueberry (BBE) cultivars (‘Centurion’ and ‘Maru’) were studied using pure and mixed cultures of human faecal bacteria. The results demonstrated for the first time that addition of BBE from both cultivars to broth media containing pure cultures of Lactobacillus rhamnosus and Bifidobacterium breve resulted in a significant increase (P < 0.05–0.0001) in the population size of these strains. Batch fermentation system was used to monitor the effect of BBE addition on the mixed faecal bacterial populations (obtained from healthy human donors). Addition of BBE from both cultivars to batch cultures inoculated with mixed human faecal cultures resulted in a significant increase in the number of lactobacilli (P < 0.01–0.0001) and bifidobacteria (P < 0.05–0.0001). Furthermore, a significant influence on the population size of lactobacilli and bifidobacteria was observed after administration of extracts from both cultivars to rats daily for 6 days in comparison with the control group. In rats gavaged orally with 4 ml kg⁻¹ day⁻¹ of BBE for 6 days, the population size of lactobacilli (P < 0.05) and bifidobacteria (P < 0.05–0.01) was increased significantly. We hypothesize that BBE could modify the bacterial profile by increasing the numbers of beneficial bacteria and thereby improving gut health.     

Effects of potassium deficiency on the enzymatic changes in developing cotton fibers

Although effects of potassium (K) on cotton growth have been explored extensively, the effects of K deficiency on the physiological changes closely related to cotton fiber development are lacking. Thus, a 2-year field experiment was conducted with two cotton cultivars (Simian 3 and Siza 3) under 0 kg K₂O ha^?1 (K deficiency) and 300 kg K₂O ha^?1 (K sufficiency). The results showed that tonoplast adenosine triphosphatase (V-ATPase), pyrophosphatase (PPase), plasma membrane H⁺-ATPase (PM H⁺-ATPase), phosphoenolpyruvate carboxylase (PEPC), sucrose synthesis (SuSy) and vacuolar invertase (V-INV) were highly sensitive to K deficiency. The decreases in those enzymes resulted in low malate and soluble sugar contents, which together with low K concentration declined the driving force for fiber elongation, leading to significantly lower fiber length in the 0 kg K₂O ha^?1 treatment. The activity of sucrose phosphate synthase (SPS) was obviously increased by K deficiency before 20 days post anthesis (DPA), which could partly explain the acceleration of fiber cellulose synthesis and the increase in fiber strength in the 0 kg K₂O ha^?1 treatment in the early stage. However, SPS activity was decreased by K deficiency after 20 DPA and SuSy activity was reduced by K deficiency at any sampling date, resulting in low fiber strength in the end. Compared with Simian 3, the enzymes V-ATPase, PPase, PM H⁺-ATPase, PEPC and SuSy during fiber elongation stage were more sensitive to K deficiency in Siza 3, and the enzymes SuSy and SPS during fiber-thickening stage were more sensitive to K deficiency in Siza 3, which were the important reasons causing greater decreases in final fiber length and final fiber strength for Siza 3 than Simian 3 under K deficiency.     

Growth and carrageenan quality of <Emphasis Type="Italic">Kappaphycus striatum</Emphasis> var. <Emphasis Type="Italic">sacol</Emphasis> grown at different stocking densities,duration of culture and depth

Kappaphycus striatum var. sacol was grown in two separate studies: (1) at two stocking densities, and (2) at four different depths, each for three different durations of culture (30, 45 and 60 days) in order to determine the growth rate of the seaweed and evaluate the carrageenan content and its molecular weight. The results demonstrated that stocking density, duration of culture and depth significantly (P < 0.01) affected the growth rate, carrageenan content and molecular weight of K. striatum var. sacol. Decreasing growth rate was observed at both stocking densities and at four depths as duration of culture increased. A lower stocking density (500 g m⁻¹line⁻¹) showed a higher growth rate for the shortest durations, i.e. 30 days, as compared to those grown at a higher density. Likewise, decreasing growth rate was observed as depth increased, except at 50 cm after 60 days of culture. A 45-day culture period produced the highest molecular weight at both stocking densities (500 g m⁻¹line⁻¹ = 1,079.5 ± 31.8 kDa, 1,000 g m⁻¹line⁻¹ = 1,167 ± 270.6 kDa). ‘Sacol’ grown for 30 days at 50 cm (1,178 kDa) to 100 cm (1,200 kDa) depth showed the highest values of molecular weight of carrageenan extracted. The results suggested that K. striatum var. sacol is best grown at a stocking density of 500 g m⁻¹line⁻¹, at a depth of 50–100 cm, and for a duration of 30 days in order to provide the highest growth rate, carrageenan content and molecular weight.     

Optimization of the yield and quality of agar from Gracilariopsis lemaneiformis (Gracilariales) from the Gulf of California using an alkaline treatment

The effect of several alkali treatments on the yield, gel strength, rheology, and chemical characteristics (quality) of the agar obtained from Gracilariopsis lemaneiformis from the Gulf of California was analyzed using different alkali concentrations, temperatures and treatment times. In the first stage of the experiment, all treatments lasted 60 min and the NaOH concentrations (2.5, 3.0, 4.0, 5.0, 6.0%) and temperature (80, 90, 100°C) varied. At constant time, temperature played the predominant role, promoting an increase in agar gel strength. Based on the best treatment conditions found (4% and 5% NaOH, and 90°C and 100°C temperature), in the second stage different treatment times (15, 30, 60, 90, 120 min) were used. Since agar yields were not significantly different among temperatures and times, the optimal conditions to obtain best quality agar were those providing the highest gel strength. Treatment time played an important role in increasing gel strength. Maximum gel strength (Nikan, 954 g cm⁻²) was obtained with 5% NaOH at 100°C after 90 min of treatment, though these conditions resulted in an agar yield reduction of 25.5% relative to native agar. This treatment proved to efficiently yield G. lemaneiformis agar that will meet the commercial quality requirements regarding gel strength, 3,6 anhydrogalactose and sulfate content, as well as rheology and hysteresis. Enrique Hernández-Garibay holds a CONACyT scholarship.     

The accumulation of pigment in fiber related to proanthocyanidins synthesis for brown cotton

Brown cotton is a kind of naturally colored cotton. Because of less processing and little dying, it is more friendlier to environment than white cotton. For brown cotton, pigment accumulation in fiber is one of the most important characteristics. In this study, we selected a brown fiber line and a white fiber cultivar to determine the factor that affects the pigmentation in brown fiber. Accordingly, fibers were collected to verify the presence of PAs by p-dimethylaminocinnamaldehyde (DMACA) and toluidine blue O (TBO) staining. The PAs content and related genes expressions were determined. As a result, there were obvious differences on the aspect of PAs synthesis in fiber between white cotton and brown cotton. For white fiber, the PAs content reached maximum at 5 DPA, and then gradually decreased to zero. But for brown fiber, the PAs content was increased from 5 to 15 DPA stage, and reached the maximum at the 15 DPA stage, then gradually decreased from 15 to 40 DPA stage. On the contrary, in white cotton, PAs were synthesized in the whole developmental stage from 5 to 40 DPA. And PAs content in brown fiber were far more than that in white fiber, which may be the reason why the brown pigment accumulated in brown fiber.