红壤旱坡地桔园覆盖的生态效应及经济效益评价

柑桔是南方红壤地区栽培的主要果树种类,栽培面积达1126×106ｈｍ2。柑桔是一种常绿果树,生长量大,挂果期长,周年需要消耗大量的水分。我国南方红壤地区虽然雨水充沛,但降水季节分布不均,柑桔果实迅速生长的7～10月正是该地区雨水少、蒸发量大的伏秋干旱季节。经常性的伏秋干旱是制约我国柑桔产量和质量进一步提高的主要障碍因素之一。桔园夏秋进行秸秆覆盖可以降温[1]、保水[2]、防止杂草生长[3]等,但桔园应用地膜覆盖及常年连续覆盖对桔园的生态效应方面的研究较少,为此我们开展了这方面的工作,并通过连续3ａ的产量及产值分析覆盖桔园的经…     

北方稻田生态系统水量平衡及水分效率研究

１９９３～１９９５年研究了５种不同模式水稻田生态系统水量平衡及水分效率结果表明,不同水稻田模式其总耗水量之间有明显差异,其中节水模式和节水节肥模式较常规模式节省灌溉水达１５～２３％,水分生产效率增加３０％以上．各模式蒸发蒸腾耗水量在同一生长季内基本相同．田间结构及调控管理对其无明显影响实测水稻生育期田间蒸发蒸腾量与计算的可能蒸发蒸腾量相差不过５％。     

北方稻田生态系统研究Ⅱ．稻萍结合系统细绿萍共生固N量研究

对稻萍结合系统细绿萍共生固Ｎ量研究表明,萍的固Ｎ力在整个生长季不同时期有所变化．最高固Ｎ率出现在６月初,萍固Ｎ量随其接种量和水稻行距增加而增加．５０～１０ｃｍ宽窄行交替的水稻行距和１５００ｋｇ·ｈｍ－２的萍接种量的稻萍结合系统的总固Ｎ量为１０７．１ｋｇ·ｈｍ－２,而３０ｃｍ等行距的３２５ｋｇ·ｈｍ－２的萍接种量的稻－萍结合系统的总固Ｎ量仅为３６．０ｋｇ·ｈｍ－２     

不同育秧方式和插植密度下晚籼稻群体动态结构的研究

不同育秧方式和插植密度下晚籼稻群体动态结构存在差异。旱育秧群体分蘖速度快,分蘖能力强。稀植可促进个体分蘖多发、有效穗数增多,但旱育稀植并无分蘖早发的优势。旱育稀植使主茎基部叶片变短而上部叶片变长,生育后期叶面积消长平稳,地上部干物质积累较多。旱育秧、稀植都使主茎叶总数增多,全生育期延长。     

水稻叶片对模拟酸雨伤害的生理反应

水稻暴露于ｐＨ２．５～４．２的模拟酸雨中２个月后测定表明：叶片叶绿素含量下降,细胞液离子外渗率增加,气孔阻抗增高,蒸腾速率降低。不同叶位的水稻叶片对模拟酸雨的敏感性不同,杂交稻（汕优６３）对模拟酸雨的敏感性较粳稻（中粳８６４）高     

Intraspecific Variation in Chemical Attraction of Rice to Insect Predators

The olfactory response of predators of the brown planthopper,Nilaparvata lugensStål, to different genotypes of rice (14 cultivars and breeding lines ofOryza sativaL. and 1 wild species,Oryza nivaraSharma et Shastry) was measured in an airflow olfactometer. Odor from rice plants attracted more females of the mirid predatorCyrtorhinus lividipennisReuter than plain air (control) on only 6 of the 15 rice genotypes. Orientation ofC. lividipennistoward volatiles of certain rice genotypes was apparent even when the plants were free of the brown planthopper. However, the predator distinguished between prey-infested and uninfested plants and preferred plants with eggs over plants with nymphs. The predator did not distinguish different stages of plant growth (vegetative, booting, or flowering). Plants artificially injured to simulate brown planthopper oviposition wounds were not as attractive to the predator as plants on which the planthopper had oviposited. The preassay preconditioning on the cultivar TN1 did not produce a predator bias for this genotype. This suggests that rearing effects or chemically mediated associative learning reported for some natural enemies did not influenceC. lividipennis'host response. Results with another predator, the coccinellidMicraspis hirashimaiSasaji, produced less consistent behavior. Planthopper-infested plants attracted more females ofM. hirashimaithan unifested plants in only 1 of the 12 rice genotypes evaluated. Implications for augmenting predators by rice cultivar selection and modification are discussed.     

The role of active oxygen in iron tolerance of rice (Oryza sauva L.)

Summary Iron tolerance of rice (Oryza sativa L.) was investigated using an oxygen depleted hydroculture system. Treatment with high concentrations of Fe²⁺ induced yellowing and bronzing symptoms as well as iron coatings at the root surface. Root and shoot growth were inhibited by increasing iron concentration in the medium. All symptoms were more pronounced in an iron sensitive cultivar (IR 64) compared to an iron tolerant one (IR 9764-45-2). Superoxide dismutase and peroxidase activity of root extracts of IR 97 were about twice that of IR 64 in untreated control plants. No significant increase of peroxidase activity was detected with increasing iron concentration in the medium. Catalase activity of IR 64 was slightly higher than that of IR 97, independent of iron concentration.Abbreviations SOD Superoxide dismutase (EC 1.15.1.1) - POD peroxidase (EC 1.11.1.7) - EDTA ethylenediamintetraacetic acid - fwt fresh weight - Hepes (N-[2-hydroxyethyl]piperazine-N-[2-ethanesulfonic acid]) - BSA bovine serum albumin - IR 97 IR 9764-45-2 an iron tolerant rice cultivar - IR 64 iron sensitive rice cultivar - PM plasma membrane     

Effects of salinity on seed set in rice

Salinity reduces fertility in rice (Oryza sativa L.), but little is known of the underlying cause(s). In order to determine the relative importance of pollen viability and stigmatic receptivity for seed setting, plants of the rice cultivar IR36 were treated with ‘artificial’ sea water (0,10, 25 or 5Omol^?3 with respect to NaCl) from 1 month after germination until the main tiller flowered. An increase in the salinity in the medium resulted in a decrease in the number of fertile florets and in the viability of pollen as determined both by pollen germination and by pollen staining with the tetrazolium salt 3-(4,5-dimethyl-ithyazolyl)-2,5-diphenyl monotetrazolium bromide. In order to assess the effects of salt on stigmas, seed production was measured for salt-grown and non-salt-grown female plants pollinated with viable pollen (from plants grown in the absence of salt). The percentage of seed set was reduced by 38% when the female plants were grown in 1Omol m^?3 Na and by 72% at 25mol m^?3 Na: no seed setting was recorded for plants grown in 50mol m^?3 Na. Comparisons between crosses involving male and female parents grown at different salinities indicated that effects on the female plants dominated those on pollinator plants. Mineral analysis of leaves of different ages showed that there was a gradient of K concentration from leaf to leaf which was opposite to that of Na and Cl at all levels of applied salinity: K was maximal in the flag leaf, where Na and Cl were minimal. Analysis also revealed that there was an increase in the concentrations of Na and Cl and a decrease in the concentration of K in the pollen grains and stigmas of plants subjected to saline conditions. Correlations between the concentration of Na and Cl in pollen and pollen staining and pollen germination in vitro suggest that Na and Cl perse were responsible for the poor viability. The change in ionic concentrations in pollen and stigmas was much larger than that in the younger leaves, and in particular very much larger than that in the lemmas and paleas.     

Potential and pitfalls of trying to extend symbiotic interactions of nitrogen-fixing organisms to presently non-nodulated plants,such as rice

It has been a long-standing goal in the field of biological nitrogen fixation to extend nitrogen-fixing symbioses to presently non-nodulated cereal plants, such as rice. A number of researchers have recently described the induction of nodule-like structures on the roots of cereals primarily by rhizobia, in either the presence or absence of plant cell-wall-degrading enzymes or plant hormones. We briefly review this research and discuss the potential problems associated with the introduction of nitrogen-fixing microbes in novel physiological environments, such as rice roots. The results of experiments carried out in China on the induction of nodule-like structures on rice roots by rhizobia are highlighted. In addition, we present preliminary results of a series of experiments designed to repeat and evaluate these results using a variety of microscopic techniques and molecular genetic approaches.