Screening technique for differentiating the degree of spikelet filling in rice

Summary Fully filled spikelets were determined by specific gravity method in some rice varieties. As specific gravity increased, the filled spikelets decreased while the test weight (1000-grain weight) increased. The potential test weight was found to be more than the weight known for the variety. Different grades of grain were characterised as (i) average (ii) good and (iii) Very good based on the degree of spikelet filling. The fully fitted spikelets were found to be lower in all the varieties tested and the partially filled but useful for yield calculations were higher. The grain grade index denotes the proportion of fully filled spikelets recovered at 1.18 specific gravity to the total number of spikelets formed. It was suggested that this inded is useful as a screening tool in varietal improvement programme for identifying high yield potential plants.     

Efficient selection intensity in early generation index selection in groundnut (Arachis hypogaea L.)

Summary The F₂ potential of single and three-way crosses was evaluated using a set of physiological and yield components. Results were based on an index of selection using (a) only yield components and (b) both physiological and yield components. The indices were constructed using the percentage improvement of F₂ over the better parent of the corresponding F₁ cross for every character. The performance of F₂ plants assessed by the expected value of the regression index was ranked in descending order to provide a ranked F₂ distribution (FRD). The FRD was divided into four equal parts, T₂₅ (top 25%), T₅₀ (26–50%), T₇₅ (51–75%) and T₁₀₀ (76–100%). F₃ families derived from F₂ plants in T₂₅ were found to provide a higher frequency of selections for pod number than T₅₀, T₇₅ and T₁₀₀. The frequency of selections was higher in three-way than single crosses. Selection index based on physiological and yield components was more efficient in trapping F₂ plants providing selections in F₃ than the index based on yield components only. The results brought out the importance of bunch x bunch crosses as a complement to the usually advocated bunch x runner ones.     

Stomatal response to air humidity and its relation to stomatal density in a wide range of warm climate species

The gas exchange of 19 widely different warm climate species was observed at different leaf to air vapour pressure deficits (VPD). In all species stomata tended to close as VPD increased resulting in a decrease in net photosynthesis. The absolute reduction in leaf conductance per unit increase in VPD was greatest in those species which had a large leaf conductance at low VPDs. This would be expected even if stomata of all species were equally sensitive. However the percentage reduction in net photosynthesis (used as a measure of the relative sensitivity of stomata of the different species) was also closely related to the maximal conductance at low VPD. Similarily the relative sensitivity of stomata to changes in VPD was closely related to the weighted stomatal density or crowding index.The hypothesis is presented that stomatal closure at different VPDs is related to peristomatal evaporation coupled with a high resistance between the epidermis and the mesophyll and low resistance between the stomatal apparatus and the epidermal cells. This hypothesis is consistent with the greater relative sensitivity of stomata on leaves with a high crowding index.The results and the hypothesis are discussed in the light of selection, for optimal productivity under differing conditions of relative humidity and soil water availablility, by observation of stomatal density and distribution on the two sides of the leaf.Visiting scientist, plant physiologist and research assitant of the Cassava Program     

“同时蒸馏-萃取”分析茉莉花香成分

用一种经过改进的“同时蒸馏-萃取”仪提取了茉莉花的香成分,以 GC/MS 和 Kovats保留指数法鉴定了提取物中的28个化学成分。主要成分为:芳樟醇、乙酸苯甲酯、顺-石竹萜烯、榧烯醇、苯甲酸顺-3-己烯酯、邻氨基苯甲酸甲酯、二十三烯-11及吲哚。讨论了鲜花香成分和植物精油的采集与分析方法。     

Toxic effects of 2-methyl-4-dimethylaminoazobenzene in normal and partially hepatectomized rats

In order to obtain a more precise definition of the conditions under which 2-methyl-4-dimethylaminoazobenzene (2-Me-DAB) and liver cell proliferation play a role in the initiation of hepatocarcinogenesis, the toxicity of 2-Me-DAB for normal and partially hepatectomized rats was investigated. Continuous feeding of a basal low protein, low riboflavin diet supplemented with 2-Me-DAB was found to be highly toxic for male albino rats. All animals fed on such a diet died before 200 days. Sham operation and partial hepatectomy (PH) at 30 days of 2-Me-DAB feeding reduced the median survival time from 122 days to 107 and 94 days, respectively. Transfer to the basal diet after 30 days of 2-Me-DAB feeding and PH prolonged the median survival time to 216 days while 97% of the rats returned to the normal complete diet after the same treatments survived for more than 300 days. 2-Me-DAB was not necrogenic and there was no evidence of reparative proliferation or hepatic tumor formation in any group. Feeding rats with the 2-Me-DAB containing diet for 1 month delayed and strongly inhibited the mitotic response of the liver to the stimulus of partial hepatectomy. This is the result of a blockage of the cells in G1 as revealed by the fact that only 1% of the hepatocytes became labeled when 2-Me-DAB fed animals were injected with tritiated thymidine prior to sacrifice at 24 h post-hepatectomy, as compared to 40% in rats fed the normal or the control basal diet. This inhibitory effect of 2-Me-DAB is reversible however since rats returned to the normal diet for 1 or 2 months after 2-Me-DAB feeding showed percentages of mitoses and labeling indices comparable to those of control animals following PH. The number of abnormal mitoses was high (13%) in regenerating livers of rats fed 2-Me-DAB and the lesions responsible for this effect are apparently not repaired since 2-Me-DAB fed rats partially hepatectomized after being transferred to the normal diet for 1 or 2 months showed the same number of mitotic irregularities. The present results suggest that assays with 2-Me-DAB as 'pure initiator' or agent of selective toxicity should be pursued in attempts to improve existing experimental models of hepatocarcinogenesis.     

贵州部分森林群落物种多样性初步研究

 本文根据贵州省178个森林群落样地的数据研究了群落物种的多样性。测定的指标有群 落物种丰富度,群落Simpson多样性指数和群落均匀度。测定结果表明;不同垂直带生物气 候条件下的森林群落有不同的多样性。相同垂直带生物气候条件下,基质生境相同时,不同森林植被亚型的群落的多样性近似,基质生境不同时,群落多样性则不同;同一群落类型的各个样地的多样性也有变化,结构不同的群落个体,其多样性指数不同,演替趋势也不同。乔木第二亚层的多样性普遍地高于乔木第一亚层。同一演替系列中,越接近顶极阶段多样性越高。多样性指数与群落物种丰富度,均匀度呈紧密的正相关,与群落个体总数没有相关。认为多样性测定在比较、说明群落的结构、类型、组织特征、生境、演替等方面有一定意义。     

Dry matter and nitrogen accumulation and partitioning in selected soybean genotypes of different derivation

Summary Experiments were conducted to determine if changes in the accumulation and partitioning of dry matter (DM) and nitrogen (N) in soybean [Glycine max (L.) Merr.] were associated with agronomic improvements and to assess the degree of genetic variation present for these traits. Fifteen maturity group II soybean genotypes including three ancestral cultivars, three modern cultivars, and nine agronomically superior plant introductions (PI's) were grown in replicated tests at four locations in the eastern U.S. The DM and N of stems, pod walls, and seeds were determined at maturity, and the apparent harvest indices (HI) and the apparent nitrogen harvest indices (NHI) were calculated. Pod DM partitioning was calculated as the ratio of seed DM to total pod DM and pod N partitioning was the ratio of seed N to total pod N. The mean DM accumulation of the modern cultivars was significantly greater than that of the ancestral cultivars and PI's. The apparent HI and the pod DM partitioning of both the modern and ancestral cultivars were significantly higher than that of the PI's. The three modern cultivars demonstrated the highest N accumulation. As a group, the modern cultivars consistently showed maximal accumulation and partitioning of DM and N suggesting that these physiological traits are associated with agronomic improvement. No individual PI was found to possess DM or N accumulation or partitioning which significantly exceeded the best modern cultivar or ancestral cultivar, indicating that genotypes with accumulation or partitioning characteristics which exceed available germplasm may be difficult to identify. Seed yield was correlated (P<0.05) with both DM (r=0.61) and N (r=0.57) accumulation.     

In vitro response of leaf tissues from Lolium multiflorum — a comparison with leaf segment position,leaf age and in vivo mitotic activity

Summary Immature gramineous leaves provide a convenient system for comparing the response of cells in culture with their state of differentiation. Callusing frequency is compared with leaf segment position, leaf age and in vivo mitotic activity in Lolium multiflorum. (1) In a succession of one millimeter sections from the immature leaf base, callus was formed from the first and second sections but not the third or subsequent sections. The frequency of those explants callusing decreased with distance from the base of the leaf and with leaf age (or leaf extension growth). (2) In vivo, the proportion of cells in mitosis declined from around 10–14% at the base of young leaves to zero at 5 mm from the base and beyond. Mitotic activity also declined in leaves as they aged, and dividing cells were not observed in leaves 30 days from initiation or older. (3) A high frequency of callus formation was associated with a high mitotic index in the explant. But for corresponding mitotic indices, cells further away from the leaf base were less responsive in culture. (4) It is proposed that cells are becoming differentiated even in highly meristematically active regions of the leaf and concomitantly losing their ability to respond in culture.     

Regulation by kinetin and abcisic acid of correlative senescence in relation to grain maturation,source-sink relationship and yield of rice (Oryza sativa L.)

When kinetin was applied to the source organ (flag leaf) of rice (Oryza sativa L. cv. Ratna), foliar senescence was delayed and grain yield per plant (as evidenced by grain weight, grain/straw weight ratio and 1,000 grain growth) was increased through the increase of sink activity (increase in dry weight of the grains/plant), duration of sink capacity as well as photosynthetic ability of the glumes (as determined by the chlorophyll content of the glumes of the developing grains). However, application of kinetin to the sink organs (fruits), promoted senescence of the source but increased the yield by increasing the sink capacity and 1,000 grain growth mostly at the earlier stage of reproductive development. Lower sterility percentage was associated with higher grain yield of the plant by kinetin treatments. ABA applied either to the source or the sink promoted leaf senescence and reduced the grain yield by reducing the sink activity, harvest index, sink capacity duration and increasing the sterility percentage. Thousand grain dry weight at harvest did not vary significantly amongst the treatments. It was concluded that nutrient drainage was associated with the correlative influence of fruit on the monocarpic senescence of rice plant and that a competetion for differential allocation of cytokinin and ABA in the source and sink organs initiates this senescence syndrome.     

水蒸汽蒸馏巴柑檬叶和果皮精油化学成分的研究

巴柑檬是我们第一次从国外引种成功的一种名贵香料植物。用色谱-质谱-计算机联用技术、毛细管气相色谱保留指数法和标准品叠加法分析了水蒸汽蒸馏巴柑檬叶和果皮精油的化学成分。从叶和果皮精油分离出来的220个和200个成分中,分别鉴定出48个和57个成分。鉴定组分的含量分别占叶和果皮精油的99.80％和98.54％。叶精油与果皮精油在化学成分方面的主要区别是叶油中萜烃化合物含量较低,而萜醇类化合物含量较高。