Responses of germination and radicle growth of two Populus species to water potential and salinity

Abstract The effects of water potential, NaCl and Na2SO4 on germination and radicle growth of two riparian tree species, Populus euphratica Oliv. and P. pruinosa Schrenk （Salicaceae）, were tested. Growth chamber studies revealed an optimum temperature range for seed germination of both species between 15-35℃. The final germination percentage of both species decreases with decreasing water potential in all types of solution applied in the experiments. P. pruinosa was less tolerant to low ψw stress than P. euphratica, especially in salt solutions. Germination percentages fell below 20% for P. pruinosa at -0.6 MPa （NaCl） or -0.4 MPa （Na2SO4） and for P. euphratica at -1.2 MPa （NaCl） or -0.6 MPa （Na2SO4）. Radicle growth of both species was inhibited by high concentrations of PEG1 NaCl and Na2SO4. However, growth was enhanced at -0.13 and -0.29 MPa in PEG or at -0.13 MPa in NaCl solutions compared to distilled water. Radicle growth of P. euphratica was higher than that of P pruinosa. Germination and radicle growth of both species exhibited ion toxicity. Na2SO4 was more toxic than iso-osmotic solutions of NaCl. Radicle growth proved to be more sensitive than seed germination. Thus, flooding does not only yield the necessary soil moisture for germination but also favors seedling establishment of both species through leaching of salts from the soil surface. The different sensitivity of the species during their early growth stages might, moreover, contribute to the observed differences in their distribution in the Talim Basin （northwest China）.

Forest gaps regulate seed germination rate and radicle growth of an endangered plant species in a subtropical natural forest

The survival rate of Castanopsis kawakamii from seed to seedling is relatively low,leading to difficulties in the regeneration of its natural forests.Forest gaps play a vital role in plant regeneration and biodiversity maintenance in forest ecosystems.Unfortunately,our understanding of the effects of gap size and within-gap position on the seed germination and radicle growth of C.kawakamii is still limited.In particular,our knowledge on the relationship between gap size and environmental factors and their influence on seed germination and radicle growth is incomplete.In the present study,we studied the influences of forest gaps and within-gap position on seed regeneration on the germination and radicle growth of an endangered species C.kawakamii in a subtropical natural forest in China.We selected three large gaps(LG,gap size above 200 m^(2)),three medium gaps(MG,gap size 50-100 m^(2)),three small gaps(SG,gap size 30-50 m^(2)),and non-gap(NG),and planted the seeds of C.kawakamii in five positions within each gap.The results showed that(1)the influence of forest gaps on seed germination rate was,from highest to lowest,medium gaps(51%),non-gap(47%),small gaps(40%)and large gaps(17%),and the seed germination rate was the highest in all positions in medium gaps,with the exception of the east position.(2)Radicle length in forest gaps was,from highest to lowest,medium gaps,small gaps,large gaps and non-gap,and it was the highest in the east,south,west and north positions of medium gaps.(3)Canopy openness(gap size)and air temperature were the main factors influencing seed germination and radicle growth of C.kawakamii.We concluded that medium-sized gaps were the most suitable for seed germination and radicle growth of C.kawakamii,and they promote the regeneration of this endangered species in the investigated natural forest.

Isolation of development-related genes in somatic embryo radicle of carrot (Daucus carota L.) using modified cDNA RDA

Using modified cDNA RDA capitalizing on the high affinity of streptavidin for biotin and magnetic-absorption-based separation, we have obtained four bands of specifically expressed cDNA in the carrot somatic embryo deregulated for 12 h, which were designated as NR-1, NR-2, NR-3 and NR-4, respectively. As revealed by homology analysis of their DNA sequences after cloning them into pBS, remarkable homology was demonstrated in NR-2, NR-3 and NR-4 with the genes coding for LEA (late embryogenesis abundant protein), Dna J and xyloglucan endo-trans-glycosylase in plants. On the other hand, NR-1 showing no homology with any known sequence may have come from unknown genes. Using 32P-labeled NR-1 as probe, hybridization with cDNA fragment population has shown that we have actually cloned a new gene fragment related to radicle development. As shown by further Southern hybridization, these genes may be present in carrot genome in the form of single or low copies.

Radicle pruning by seed-eating animals helps oak seedlings absorb more soil nutrient

Although radicle pruning has well been observed in plant-animal interactions,research has not been conducted to determine how radicle pruning by seed-eating animals regulates nutrition mobilization of cotyledonary reserves and absorption of soil nutrients.We used stable nitrogen isotopes to test how acorns of early-germinating oak species(Quercus variabilis,Q.aliena,and Q.mogolica)trade off nutrients in the cotyledons and those in the soil in response to radicle pruning by seed-eating rodents.Radicle pruning by rodents resulted in root branching in the 3 early-germinating oak species.Moreover,radicle pruning increased shoot dry weight and substantially reduced the root-to-shoot ratio of oak species.Corresponding to the decreased dry weight of roots and root-to-shoot ratio,the dry weight of the remnant cotyledons was higher after radicle pruning in the 3 oak species.We provided first evidence that radicle pruning by seed-eating animals improved seedling performance of early-germinating oaks by increasing absorption of nutrients from soil.The results indicate that early-germinating oak seedlings trade off nutrition budget by altering nutrient absorption from soil and reserve mobilization from cotyledons in response to radicle pruning by seed-eating animals.Our study provided new insight into the nutrition allocation mechanism of young seedlings in response to radicle pruning by seed-eating animals,reflecting a mutualistic interaction between early-germinating oak and food-hoarding animals.

Evaluation on Sixty-eight Rice Germplasms in Cold Tolerance at Germination Stage

Sixty-eight rice germplasms were used for cold tolerance evaluation at the germination stage in laboratory. Seeds of rice germplasms germinated at three different temperatures containing low temperature （constant 13°C for 28 days）, alternative temperature （a temperature cycle of 12 h at 20°C and 12 h at 23°C for 14 days） and control （constant 26°C for 7 days）. Analysis of variance revealed that temperature had a significant effect on germination rate, coleoptile length and radicle length. Germination rate was strongly affected by the low temperature and alternative treatments. Stress of low temperature at the germination stage on the tested rice germplasms caused a reduction in final germination rate and the lengths of coleoptile and radicle. The normal and healthy seeds began to germinate within 36 h after imbibition and germination were completed on the 7th day in the control, but delayed under the low and alternative temperature treatments. The low and alternative temperature treatments delayed the growth of coleoptile and radicle compared to the control, and the average lengths of coleoptile and radicule were strongly inhibited with the decreasing temperature in all of the tested germplasms. Taichung, a semi-dwarf, low amylose content and early maturing rice variety, showed a significantly higher germination rate at the three temperature treatments and its coleoptile length was significantly higher than other germplasms.

Effects of Natural Brassinolide on Seed Germination and Hypocotyl Elongation of Beans

Seeds of soybeans and mung beans were soaked into five different concentrations （0, 0.05, 0.10, 0.20, 0.30 mg/L） of natural brassinolide （ NBR ） solution. According to the results, natural brassinolide treatment could improve seed germination rate and hypocotyl-radicle ratio of soybeans and mung beans and promote the growth of sprouts. To be specific, seed germination rate of soybeans reached the highest in 0.05 mg/L natural brassinolide treatment, which was im- proved by 25.0 percentage points compared with the control group, and the sprout length was improved by 4.33 em; 0.30 mg/L natural brassinolide exhibited the most significant promotion effect on seed germination and sprout growth of mung beans, seed germination rate was improved by 18.3 percentage points and sprout length was improved by 7.29 cm; hypocotyl-radiele ratio of soybean and mung bean sprouts reached the highest （2.96, 1.43 ） in 0.05 mg/L natural brassinolide treatment.

Bile peritonitis due to intra-hepatic bile duct rupture

Generalized biliary peritonitis is a serious intra-abdominal emergency. Most of them occur due to duodenal ulcer perforation and rapidly evolve into bacterial peritonitis due to contamination by gut organisms and food. In this situation, recognition of the pathology and its treatment is straightforward and is usually associated with a good outcome. There are a few unusual causes of biliary peritonitis, of which rupture of the biliary tree is one.We describe a rare case of biliary peritonitis due to rupture of an intra-hepatic biliary radical. Unusual causes of peritonitis do interrupt our daily routine emergency surgical experience. Rapid recognition of the presence of peritonitis, adequate resuscitation, recognition of operative findings, establishment of biliary anatomy, and performance of a meticulous surgical procedure resulted in a good outcome.

Emergence and Seedling Characteristics of Maize Native to the Southwestern US

Locally adapted maize landraces, which are associated with Native American groups, were traditionally planted deeply, reportedly up to 45 cm deep. Crop resources such as these should be evaluated for possible use in future sustainable farming practices. Cold temperatures often delay maize (Zea mays L.) planting in the Corn Belt, possibly reducing yield potential, and spring frost and hail can damage early plantings. If producers could plant deeper and earlier in the spring, the planting season period could be extended and the potential for frost damage reduced because the growing point would be insulated below the soil surface for a longer period of time. The emergence capabilities of eleven Native American landraces were evaluated at various planting depths and compared to one Corn Belt line, BSSS-53. Emergence from depths between 5 and 45 cm was evaluated in a growth chamber study. Seedling dry matter partitioning and morphological characteristics were also examined. A field study was then performed to further test those landraces that successfully emerged (≥ 75%) from the 25 cm depth in the growth chamber. Results indicate that some of the evaluated Native American landraces have a greater capacity to emerge from depth than BSSS-53. Emergence capacity was not related to initial seed weight. Mesocotyl elongation largely accounted for successful emergence from greater planting depths. The landraces partitioned relatively more dry matter to roots than shoots compared to BSSS-53. These results suggest that several of these Native American landraces may be useful for the development of maize varieties more tolerant to deep planting.

Efficient, Season-Independent Seed Germination in Black Cohosh (<i>Actaea racemosa</i>L.)

Seed germination in black cohosh was systematically examined in eighteen populations including 15 USDA accessions with an effective protocol for the consistent, season independent germination of this valuable alternative specialty crop. Two in vitro approaches were investigated for breaking the complex double dormancy of black cohosh seeds for yearround germination of plants for increased cultivation and laboratory studies. The first approach was a two-step alternating temperature stratification in which surface sterilized seeds were incubated in darkness at 25?C for two weeks followed by incubation at alternating temperatures of 20?C and 8?C for 12-hour periods with a 16-hour photoperiod for 12 months. The second was a three-step-approach that involved initial stratification of seeds in darkness at 25?C for two weeks, followed by incubation at 4?C in darkness for 3 -4 months and then cultivation at 25?C with a 16-hour photoperiod to generate seedlings. Although both approaches broke double dormancy for black cohosh seed germination, the three-step-stratification technique yielded higher percentage seed germination in less time when compared to the two-step scheme, including for seeds stored over two years. Additional factors of critical importance for efficient germination included the selection of healthy and viable seeds, as well as thorough but non-excessive surface sterilization to control bacterial and fungal contamination. The in vitro approach for black cohosh germination allowed year-round cultivation and culture of a number of different genotypic accessions to enable laboratory based studies on cell culture and transformation approaches to aid in deciphering gene-metabolite relationships in this important medicinal plant.

The Allelopathic Potential of Hairy Vetch (Vicia villosa Roth.) Mulch

Hairy vetch (Vicia villosa Roth.) has been recognized as a good candidate for weed suppressive mulch in organic no-till cropping systems. In our study, the allelopathic potential of hairy vetch, fall rye (Secale cereale L.) and winter wheat (Triticum aestivum L.) (extracted species) were evaluated at both vegetative and reproductive developmental stages (extract stage) based on the germination and radicle elongation of five response species using aqueous extracts in soil microcosms. Our study found hairy vetch shoot extract to have little allelopathic potential compared to fall rye or winter wheat, both species for which the allelopathic potential is well documented. Interestingly, hairy vetch was the only extracted species to increase in allelopathic suppression of radicle elongation at the reproductive stage when plant biomass is near maximum. This result was conceivably due to the increased concentration of the putative allelochemical cyanamide in reproductive tissue. Chemical inhibition of radicle elongation in this extract, however, was only observed in the domesticated response species wheat (Triticum aestivum L.) and canola (Brassica napus L.). The allelopathic effect on germination varied and depended on extracted species, extract stage, and response species;whereas the effect on radicle elongation was similar among extracted species, yet unique within response species. This research demonstrated that allelopathy studies should include multiple allelopathic and response species to accurately quantify the magnitude of chemical effects among allelopathic species and to rule out potential phytotoxic chemical defense/detoxification mechanisms that exist in some response species.

Importance of the Role of Gibberellic Acid and Potassium Nitrate in Seed Germination Habanero

The habanero chili （Capsicum chinense Jacq.） is a species of great demand in the domestic and international markets. One problem in the cultivation is low percentage of seed germination. There is little information on the use of promoters and imbibition time to increase this parameter, without compromising the quality of seedlings. In this context, authors assessed the independent effect of GAs （gibberellic acid） and KNOs at concentrations of 0, 100, 200, 300, 400 and 500 mg·L1. Seeds without preconditioning were the witness. The experimental unit was a Petri dish with 50 seeds on filter paper placed equidistant. There were three replicates per treatment and the experimental design was randomized complete block. Imbibition time was 24 h. The experimental units were kept in an incubator at 22 ± 2 ℃. From the time of planting and for periods of 24 h for 14 d, experimental units were reviewed to determine the time at the beginning of germination and the total cumulative percentage. The authors also determined the number of normal and abnormal seedlings, the length of hypocotyl and radicle, weight of fresh and dry matter of seedlings. On the fifth day after sowing in vitro, concentrations of 500 mg·L^-1 of GAs, 300 and 400 mg·L^-1 KNO3, increased 208% the percentage of seed germination of habanero chile. On day 14 after sowing in vitro concentrations of 500 mg·L^-1 GA3, 300 and 400 mg·L^-1 KNO3, increased 23% normal seedlings and 40% dry matter thereof, with respect to seeds obtained without preconditioning. Unconditioned seeds before sowing produced 125% more seedlings.

Effect of leaf and bark aqueous extract of Anogeissus latifolia on growth performance of Vigna unguiculata

The present study was carried out to assess the effect of leaf and bark aqueous extract of Anogeissus latifolia tree on Vigna unguiculata traditional crop to understand the suitability of treecrop combination in agricultural fields. Different concentrations of leaf (1%, 3% and 5%) and bark (1%, 3% and 5%) aqueous extract of A. latifolia were used to study radicle and plumule growth of Vigna unguiculata. The leaf and bark aqueous extract have shown minimum allelopathic effect on V. unguiculata and suppressed/stimulated radicle and plumule growth under different concentrations. The wide distribution of Anogeissus latifolia in a subtropical region of Garhwal Himalaya, provides good fodder fuel wood and timber to the villagers. Therefore introducing Anogeissus latifolia in agricultural field and maintaining the existed trees at boundaries of agricultural fields can be useful to the villagers requirements for the villages and wherever the possible allopathic effect exit can be minimized by lopping the branches of trees and use of naturally flecked off bark for fuel wood purposes.

茎枯病菌毒素制备及对芦笋愈伤组织抗性诱导的研究

Toxin-producing culture medium and culture time for Phomopsis asparagi were optimized, and theeffect of the pathogen toxin on asparagus callus was investigated in the study. It was found that the toxin pro-duced from culture for 12 days in the Fries medium showed the strongest inhibition effect on asparagus radicle.Toxin caused callus of ＇ Apollo＇ , ＇ Champion＇ and ＇ NJ987＇ browning. Resistance of the callus of the threevarieties to toxin could be induced by toxin treatment. Toxin concentration for resistant callus selection was30% -40%.

ABA-Mediated Inhibition of Germination Is Related to the Inhibition of Genes Encoding Cell-Wall Biosynthetic and Architecture： Modifying Enzymes and Structural Proteins in Medicago truncatula Embryo Axis

Radicle emergence and reserves mobilization are two distinct programmes that are thought to control germination. Both programs are influenced by abscissic acid （ABA） but how this hormone controls seed germination is still poorly known. Phenotypic and microscopic observations of the embryo axis of Medicago truncatula during germination in mitotic inhibition condition triggered by 10 μM oryzalin showed that cell division was not required to allow radicle emergence. A suppressive subtractive hybridization showed that more than 10% of up-regulated genes in the embryo axis encoded proteins related to cell-wall biosynthesis. The expression of α-expansins, pectin-esterase, xylogucan-endotransglycosidase, cellulose synthase, and extensins was monitored in the embryo axis of seeds germinated on water, constant and transitory ABA. These genes were overexpressed before completion of germination in the control and strongly inhibited by ABA. The expression was re-established in the ABA transitory-treatment after the seeds were transferred back on water and proceeded to germination. This proves these genes as contributors to the completion of germination and strengthen the idea that cell-wall loosening and remodeling in relation to cell expansion in the embryo axis is a determinant feature in germination. Our results also showed that ABA controls germination through the control of radicle emergence, namely by inhibiting cell-wall loosening and expansion.