Plant Ideotype at Heading for Super High-Yielding Rice in Double-Cropping System in South China

The newly released super high-yielding hybrid rice combinations, Yueza 122, Fengyou 428, Peiza 67, and the super high-yielding conventional cultivars, Guangchao 3 and Shengtai 1, were grown in both early and late seasons. The morphological characters of each population were investigated at the heading stage, and the data were analyzed by using ANOVY and other statistic methods. The plant ideal morphological characters at the heading stage were established as follows: 1) for the early-season cropping, 90-105 cm plant height; 11-12 tillers per plant; 35-40 cm length and 2.1-2.2 cm width of flag leaf; 46-50 cm length and 1.8-2.1 cm width of the second leaf from the top (L2); 59-64 cm length and 1.4-1.9 cm width of the third leaf from the top (L3); 7°-14°, 18°and 20°-33°for the ideal leaf angles of the flag leaf, L2 and L3, respectively; 2) for the late-season cropping, 90-100 cm plant height; 9-15 tillers per plant; 30-41 cm length and 1.8-2.0 cm width of flag leaf; 53-61 cm length and 1.3-1.8 cm width of L2; 52-58 cm length and 1.2-1.5 cm width of L3; 9°-19°, 15°-37°and 16°-49°for the ideal leaf angles of the flag leaf,L2 and L3, respectively. The main physiological characteristics of these varieties were also analyzed.     

胡麻残茬水提液化感自毒作用研究

为探讨胡麻不同器官残茬的自毒作用,明确残茬根、茎及叶中的主要自毒物质,分别制备水提液,以蒸馏水为对照,设置不同浓度梯度水提液,用于胡麻种子萌发及幼苗生长实验,通过测定发芽势、发芽率、株高及根重等指标确定自毒效应,利用气相色谱-质谱(GC-MS)技术分析胡麻残茬根、茎及叶中的主要自毒物质。结果显示,胡麻残茬根、茎及叶水提液对自身种子萌发和幼苗生长总体上表现为"低促高抑"作用,且存在浓度效应。随着水提液浓度增加,胡麻残茬叶水提液最先到达临界浓度,其次为茎水提液,最后为根水提液。综合效应显示,胡麻不同残茬器官水提液化感自毒作用强弱关系为:残茬叶>残茬茎>残茬根。胡麻残茬根、茎及叶水提液中分别鉴定出8种、21种和14种化合物,主要包括酸类和酯类,含量最多的自毒物质为棕榈酸和邻苯二甲酸二丁酯。胡麻残茬根、茎及叶水提液对种子萌发及幼苗生长具有显著的化感自毒效应,可能是导致胡麻连作障碍的主要原因之一。     

Sowing date, harvest date and the yield of forage brassica crops

The effect of sowing date, within the period from late May to mid-August, on the DM yield of five leafy forage brassica crops sown to a stand was examined over the period 1976–78. Kale was the crop most sensitive to variation in sowing date and yields declined progressively with later sowings. There was no yield benefit from sowing rapes or stubble turnips earlier than mid- to late-June. Raphanobrassica produced yields as good as rape when sown in June. In 1978, DM yields of rape, kale and Raphanobrassica increased from September to early November, largely as a result of stem growth; kale was slower to accumulate DM than rape in late summer but continued growing longer into the autumn. The DM concentrations of all crops increased from September to December. Rape had a higher DM concentration than stubble turnip. Raphanobrassica was 10–25 g kg^-1 lower in DM concentration than rape or kale. Raphanobrassica produced 23–59% flowering plants from late-May to early-June sowing. Harvest date affected DM yield and concentration, leaf: stem ratio and flowering percentage. The effects of sowing dale on DM concentration were small.     

Leaf number as a criterion for determining defoliation time for Lolium perenne, 1. Effect of water-soluble carbohydrates and senescence

This study sought to define the optimum defoliation interval for Lolium perenne , with the maximum interval being determined by the onset of senescence, as reflected by the number of fully expanded leaves, and the minimum interval set by the replenishment of water-soluble carbohydrates (WSCs).
In a glasshouse set at 13°C/23°C night/day temperature and at a plant spacing of 94 m⁻² (3290 tillers m⁻²), the accumulation of dry matter against leaf number and days was exponential to the four-leaf stage of the regrowth cycle. Senescence commenced at the 3·5-leaf stage.
WSCs in roots, stubble and leaf showed a very significant linear relationship with leaf number. Levels of WSCs in leaves were restored to predefoliation values by the one-leaf stage, after which WSCs accumulated preferentially in the stubble, rising to 22% at the four-leaf stage.
Regrowth after 6 d was significantly greater for plants defoliated at the three-leaf stage than at the one-leaf stage, but this difference disappeared at the end of the regrowth cycle. This questions the importance of WSCs in determining the yield of ryegrass under normal rotational grazing management.
Regrowth at 6 d was related positively to stubble WSCs (r²= 0·66) and to stubble DM per tiller(r²=0·71)     

Regrowth, morphology and persistence of Grasslands Puna chicory (Cichorium intybus L.) in response to grazing frequency and intensity

Effects of different grazing frequencies and intensities on herbage production (on both a unit pasture and individual plant basis) and on persistence of chicory ( Cichorium intybus L. cv. Grasslands Puna) were studied at Palmerston North, New Zealand (latitude 40°23'S) from November 1994 to November 1995. Three experiments were conducted on the same chicory stand, sown on 12 May 1994. The main grazing experiment had two grazing intensities, hard-lax grazing (50- to 100-mm stem stubble to mid-January, and thereafter 100- to 150-mm stem stubble) and lax grazing (100- to 150-mm stem stubble), and three grazing frequencies (1-, 2- or 4-week intervals). A subsidiary plant survival experiment compared the survival of 120 marked plants in ungrazed and grazed treatments. A late autumn grazing experiment examined the effects on plant persistence in the following spring. The greatest herbage mass (leaf + stem) resulted from the 4-week grazing frequency [9640 ± 874 kg dry matter (DM) ha⁻¹], in which stem mass was reasonably low (1270 ± 410 kg DM ha⁻¹), but was significantly higher in the 4-week grazing frequency than 1- and 2-week grazing frequencies ( P < 0·01). Grazing intensity had no significant effect except on the average stem mass of individual plants when the hard-lax intensity gave a lower stem mass ( P < 0·01). There were no interactions between grazing frequency and intensity in herbage mass. Plant density declined by 35% over the growing season with the decline unaffected by grazing intensity or frequency during the season. Grazing in late autumn resulted in approximately 27% less plants the following spring. It was concluded that grazing management through the growing season cannot be used to improve persistence without compromising leaf growth rate, but that avoidance of grazing late autumn will improve the persistence of chicory.     

The influence of sward canopy structure on foraging decisions by grazing cattle. II. Regulation of bite depth

Bite depth was measured in four experiments in which grazing cows were offered, individually, patches of perennial ryegrass swards, typically 0·9 m × 0·9 m, of contrasting structural composition within linear sequences of eighteen to twenty‐seven patches. Bite depths were analysed in relation to the independent effects of pseudo‐stem height, re‐growth depth, stubble height and sward height. In vegetative swards comprising predominantly leaf, with re‐growth and stubble strata of vegetative origin, bite depth was strongly related to sward height. However, when the leaf–stem contrast between strata increased, bite depth was strongly correlated with the depth of re‐growth. Cows were observed to penetrate into a mature stubble stratum with increasing sward height, indicating that stubble height is only a partial regulator of bite depth. In an experiment designed to investigate the independent effects of pseudo‐stem and sward height, pseudo‐stem was only a partial regulator of bite depth. Evidence to support the concept that bite depth is a fixed proportion of sward height across swards of different structure was inconsistent, but there was evidence of a maximum bite depth of 0·70 of sward height. There were also indications that bite depth was conditioned by the number of bites removed. This suggested that cows initially took a cautious approach to grazing, building up bite depth with feedback over the first 20–30 bites in a new patch. Behaviour at the current patch was not affected by the characteristics of the preceding or succeeding patch in sequence.     

SYSTEMATIC TESTING OF QUALITY IN GRASS VARIETIES

Methods of testing grass varieties are discussed and the efifects of differences in management and of nitrogen fertilizer on quality are shown. In a grazing-management system with 9 cuts per season, cocksfoot was higher than perennial ryegrass in protein and fibre and lower in soluble-carbohydrate content and in vitro dry-matter digestibility throughout the season. All species showed the lowest value for digestibility in August.
Curves for digestibility in primary growth were plotted for 4 varieties of ryegrass for leaf and stem fractions. The tetraploid variety Reveille was slightly more digestible than S24 in leaf and stem throughout the period, while at ear emergence S23 was lower in digestibility in both fractions than S24.
There were significant differenees in composition and digestibility between experimental centres, but relative differences between varieties were consistent. The level of N fertilizer did not materially alter the comparison between varieties in quality data.     

水稻烯效唑浸种对秧苗影响的解剖学观察

 以30 mg/L的烯效唑(S-07)乳剂浸种24 h, 于3叶1心期取样,在扫描电镜下观察叶表皮细胞和茎横切面,在透射电镜下观察叶绿体结构。经烯效唑处理的叶表皮细胞变短,叶表皮细胞的形状由锥体变为长方体,细胞之间的间隙变得紧密。茎横切面厚度增加,薄壁细胞增大，厚度比对照增厚44.4%左右，表明S 07延缓水稻秧苗生长主要是使细胞缩短,间隙变小,而不是减少细胞数量。而抗倒性的增强,主要是由于增加茎秆壁的厚度。透射电镜观察结果表明S-07可改变叶绿体的结构,使得类囊体增多,排列致密。     

Growth and Nutrient Accumulation of Winged Bean and Velvet Bean as Cover Crops in a Subtropical Region

We examined biomass dry matter and nutrient uptake of live plant parts, leaf area index, and litter of winged bean (Psophocarpus tetragonolobus) and velvet bean (Mucuna pruriens) 12, 18, 24 and 30 weeks after sowing (WAS). The two plants had similar leaf and stem+petiole biomasses. At 30 WAS winged bean had a significantly lower pod yield than velvet bean. Between 18 and 30 WAS, winged bean produced less litter than velvet bean due to differences in growth stages. The total mulch of live parts and litter of winged bean and velvet bean completely covered the ground by 18 and 12 WAS, respectively. Compared to velvet bean, the leaf and stem+petiole of winged bean had a significantly higher N concentration; significantly higher N uptake at 24 and 30 WAS; significantly lower C/N ratio; and significantly higher P, K and Mg concentrations. In winged bean, P uptake was significantly higher in the leaf at 30 WAS and in the stem+petiole at all harvesting times. The total biomass of the leaf, stem+petiole and litter of winged bean was 317–561 g DM m-², and their N content was 12.3–17.7 g m-². The total biomass of live parts and litter of winged bean might be sufficient to suppress weeds and increase soil N. Winged bean is an appropriate legume cover crop and green manure due to its longer growing period and superior ground-covering ability and high N input.     

Effect of thermal processing and storage on digestibility of starch in whole wheat grains

Gelatinisation and retrogradation of starch in wheat flour systems and whole wheat grains were studied using DSC and the impact of these events on starch digestibility was investigated. Gelatinisation of starch was possible in wheat flours with more than 60% moisture content (dwb) and gelatinised samples had higher digestibility values. Retrogradation of starch was studied with partially and fully cooked (boiled at 100 °C for 12 min and 32 min, respectively) wheat grains that were subjected to storage at 22 °C for 48 h. Stored samples had lower digestibility values when compared to the freshly cooked counterparts. The effect of moisture on retrogradation was studied with fully cooked wheat grains that were dried to a range of moisture contents (14.6–35.9%, wwb) and stored at 20 °C for 24 h. Retrogradation enthalpy increased with increasing moisture content; however, digestibility values did not reflect the changes in retrogradation enthalpy. The possibility of estimating the degree of retrogradation in fully cooked grains (32 min cooking) was investigated using a wheat flour-water system. The retrogradation enthalpy of fully cooked grains was slightly higher than the wheat flour-water system (at a moisture content of 49%, wwb) during the course of storage at 22 °C.     

Nitrogen and Italian ryegrass.

The regrowth of Italian ryegrass was studied at weekly intervals from 2 to 14 weeks after a cut in late April when 140 kg ha^-1 N was applied. Reduction in digestibility with delay in date of harvest was due to both an increase in the proportion of cell wall and a reduction in the digestibility of the cell wall, particularly the former from week 2 to about week 5 and particularly the latter after week 5. The reduction in the digestibility of the cell wall was about equally attributable to reduction in digestibility of cellulose and to reduction in digestibility of hemicellulose. The proportion of lignin in cell wall was highly correlated with both digestibility of cellulose and digestibility of hemicellulose. The proportion of digestible cell wall in dry matter was not as constant as has sometimes been noted, increasing by about 5 percentage units from week 2 to week 5 and decreasing by about 10 percentage units from week 5 to week 13. During the latter period the decline in digestible cell wall in dry matter accounted for nearly half the decline in true digestibility of dry matter. The ratio of cellulose:hemicellulose averaged 1:0.89 and hemicellulose was more digestible than cellulose. Rate of increase in yield of cell contents appeared to diminish from about the third week of regrowth onwards, whereas the rate of increase in yield of dry matter did not begin to diminish until about the seventh week. In vitro dry matter digestibility was not increased by adding extra N to the digestion tubes, even with samples containing only 1% N in dry matter.     

A comparison of the nutritive values of early and late varieties of timothy

In vitro digestibility, fibre, lignin and protein were determined in 50 varieties of timothy differing markedly in maturity date. The grasses were field-grown as single plants and were sampled at 10% ear emergence, 30% flowering and the mature seed stage and were compared in four groups according to date of ear emergence.
Significant differences were found between maturity groups in digestibility and protein concentration particularly at the earlier growth stages. Considerable variation also occurred within maturity groups. Differences in digestibility, fibre, lignin and protein were significantly correlated with the number of days between 30 April and harvest date.
The results are discussed in the context of an appropriate evaluation scheme for timothy varieties.     

The optimal lignin quantification method to breed for an improved cell wall digestibility in perennial ryegrass

Perennial ryegrass (Lolium perenne) is an important source of protein and energy for dairy cattle. To improve the protein/energy ratio of this forage, focus is now on improving its cell wall digestibility. The in vitro assessment of the digestible fraction of the neutral detergent fibre (NDFD) is a superior method for determining the cell wall digestibility, but requires the use of ruminal fluid, which has a highly variable composition and is often not readily available. As lignin is considered the main cell wall component that impedes NDFD, we investigated whether this “subtrait” could serve as alternative breeding selection criterion to improve NDFD. Therefore, we assessed the accuracy of two lignin quantification methods: van Soest (ADL) and Klason lignin (KL). We also considered KL estimates corrected for the solubilized lignin (total lignin or TL) and non‐solubilized protein (TL'). Although the latter is considered the truest possible lignin content, it was not always the most correlated to NDFD, due to the limited accuracy of protein quantification on lignin residue. TL is most correlated to NDFD and we therefore recommend it for use in conventional breeding if NDFD determination is not a possibility. However, NDFD is still a superior selection criterion, as it combines the effect of several subtraits and not just lignin. For marker–trait association studies, a more accurate estimate of lignin content is more important than a high correlation with NDFD, but also here, TL performs best.     

Lignin modification improves the biofuel production potential in transgenic Populus tomentosa

Lignin has been recognized for its negative impact on forage digestibility, tree pulping properties, and cellulosic biofuel production, although it is the major structural component of the secondarily thickened cell walls of vascular plants. Earlier studies have demonstrated that lignin modification improves forage digestibility and poplar pulping properties. To determine whether lignin modification has beneficial effect on saccharification of lignocellulosic biomass, we pretreated and then enzymatically hydrolyzed the mature wood from transgenic poplar plants that expressed the antisense transgenes of monolignol biosynthesis genes 4-coumarate: CoA ligase (4CL) or caffeoyl CoA 3-O-methyltransferase (CCoAOMT). Firstly, a long-term field trial was set up for the transgenic plants. Over five years, the reduced trend of lignin content remained stable in all transgenic lines. And a total lignin reduction of up to 10% did not alter the growth rate or biomass yield of the transgenic poplars. In the mature wood, suppression of CCoAOMT increased saccharification potential, but 4CL down-regulation had no significantly positive effect on saccharification. Sugar yield were negatively correlated with soluble lignin content of dried, extractive-free stem biomass. These results imply that lignin modification can facilitate the process of saccharification for biofuel production in tree crops.     

Sodium carbonate pretreatment: an approach towards desilication of paddy straw and enhancement in biogas production

Lignocellulosic biomass is a useful but an inconvenient form of energy, and paddy straw (PS) is one of the most abundant lignocellulosic wastes on the earth. Lignocellulosics generally have a high content of cellulose having combustion energy of 15 kJ/g which, when converted to methane, have a combustible energy of 50 kJ/g. But lignin and silica are the main deterrents for the microbial action on the cellulose/hemi-cellulose component of PS. In order to break the protective shield made by lignin and silica and to enhance the PS digestibility, the PS was pretreated with different concentrations (2, 4, 6, 8 and 10 %) of sodium carbonate by soaking the PS in sodium carbonate solution for the periods of 24 and 48 h and simultaneously irradiating the other set with microwaves (power 720 W, temperature 180 °C) for 30 and 60 min. The change in chemical composition of PS was the factor determining the enhancement in PS digestibility. Sodium carbonate (4 %) + microwave (60 min) pretreatment was found to be the best amongst the other pretreatments with 84.9 % desilication of PS and 44.3 and 54.4 % increase in cellulose and biogas production, respectively.     

Variation in cold tolerance in Festuca rubra L.

A laboratory assessment was made of cold tolerance in seven cultivars and one natural population of red fescue, overwintered at lowland (30 m a.s.I.) or an upland (300 m a.s.l.) site.
After 5 months overwintering, plants were exposed under laboratory conditions to seven freezing temperatures, –7, –9, – 10, – 11, – 12, – 13 and – 15°C and + 2°C as control. Thawed tillers were grown in soil in glasshouse, and tiller survival and growth recorded after 28 days. Cold tolerance was estimated using LT50 values.
Tiller mortality increased with decreasing freezing temperature, with almost all tillers surviving at – 7°C and almost all dying at – 15°C. Cold hardening at the overwintering site markedly affected survival, plants overwintered at the upland site having significantly greater survival than those overwintered at the lowland site. All samples were affected to similar extent by overwintering site. The samples Aber Valley, Hawk, Merlin, Polar, and Dawson were significantly more cold tolerant than Jupiter, S59, and Highlight. Tiller production data closely resembled those for tiller survival.
For upland situations, eultivars or natural populations other than the currently recommended S59 have better cold tolerance, and may provide useful genetic resources for breeding cultivars for uplands use.     

Leaf number as a criterion for determining defoliation time for Lolium perenne: 2. Effect of defoliation frequency and height

The object of this study was to determine the importance of frequency and height of defoliation on regrowth potential of Lolium perenne. Defoliation interval was based on stage of the regrowth cycle, as indicated by leaves per tiller.
Simulated swards of Lolium perenne cv Yatsyn were grown as individual plants in a glasshouse kept at a day/night temperature of 25°C/15°C.
Treatments imposed were defoliation at 2, 5 or 12 cm residual height, and low and high water soluble carbohydrate (WSC) level obtained by varying defoliation interval, i.e. defoliating at the 1-leaf or 3-leaf stage of the regrowth cycle. Regrowth after frequent short defoliations was only 65% of the less frequently defoliated plants taken over the full regrowth cycle. This was associated with a lower stubble WSC content (2·15 vs 17·5% in stubble) and a twenty-seven-fold difference in the amount of WSC in the stubble per plant. This difference in total WSC was a combined effect of more and heavier tillers and higher WSC content in stubble of plants defoliated less frequently at the end of the regrowth cycle. The regrowth of plants with WSC levels depleted by frequent defoliation when defoliated at 2 cm was significantly below that of those defoliated at 5 and 12 cm.
The results indicate the desirability of defoliating plants at the 3-leaf stage of the regrowth cycle. This not only allows the full regrowth potential to be expressed in that growth cycle, but also in the next cycle, by allowing the replenishment of WSC reserves and optimizing tiller status. The potential to regrow appears then to be based more on the total amount of WSC than the proportion of WSC in stubble.     

秸秆还田与覆膜对土壤理化特性及玉米生长发育的影响

试验研究秸秆还田对不同覆膜时期的全膜双垄沟播玉米生长发育与土壤理化特性的影响。结果表明,经秸秆还田后全膜双垄沟播耕层土壤养分含量变化依次表现为整株还田>秸秆粉碎>免耕留茬,不同覆膜时间对土壤养分变化影响不明显;秸秆还田土壤容重明显降低但免耕留茬一膜两年用处理土壤容重增大。在玉米生育前期经秸秆还田后的土壤温度与水分均显著低于对照,其株高、茎粗与叶面积均小于对照;在玉米生育后期秸秆腐解后对土壤水分起到一个补偿效应。玉米产量表现为秋覆膜整株秸秆还田>顶凌覆膜整株秸秆还田>秋覆膜秸秆粉碎还田>顶凌覆膜秸秆粉碎还田>免耕留茬一膜两年用,秸秆还田后玉米产量较对照有增产趋势,而免耕留茬一膜两年用有减产倾向,但处理间差异不显著。     

The effect of the duration of regrowth on photosynthesis, leaf death and the average rate of growth in a rotationally grazed sward

A study was made to characterize the effect of the duration of regrowth on the pattern of changes in the major physiological processes involved in the net accumulation of herbage, and so to provide a rational basis for optimizing production under rotational grazing.
During regrowth following a severe defoliation, rates of canopy photosynthesis, and so the rate of production of new leaves, increased rapidly but there was a delay before there was a corresponding increase in the rate of leaf death. Although the amount available for harvest (crop live dry weight, W ) continued to increase as the duration of regrowth was extended from 'short' (12–13 days), through 'medium' (19–23 days) to 'long' (30-34 days), there was not a continued increase in the average growth rate – the increase in the weight of the crop, ( W – W_o ), divided by the duration of regrowth, t , In this study, the average growth rate (based on changes in the weight of lamina alone) increased as the duration of regrowth was extended from 12-13 to 19-23 days but changed little as the duration of regrowth was extended from 19-23 days to 30-34 days. In spring and summer, elongating stems increased the average growth rate (of lamina plus stem) up to 30-34 days but the accumulated stem material could not reliably be harvested by sheep.
A mathematical model was used to explain why the average growth rate is characteristically insensitive to the duration of regrowth beyond a given minimum duration. For practical purposes, we suggest from the results of this study that regrowths of at least 14 days but less than 28 days will be effective in achieving not only close to the maximum average growth rate of highly digestible material, but also in sustaining a densely tillered, leafy sward which regrows rapidly from severe defoliation and is more reliably harvested (utilized) by sheep.