Effect of thinning on growth of Acer velutinum Boiss. in northern forests of Iran

It has become necessary to develop stands of fast growing endemic species in the Caspian forests because of their reduction in area and the domestic demand of timber processing industries in Iran. Acer velutinum, an en- demic species in Iran, is often planted in monocultures or in a mixture with other endemic species. Our study was con- ducted on A. velutinum planted in Berenjestanak （control plots） and Chaibagh （thinned plots） in northern Iran in 1991. A randomized sampling method with circular sampling plots of 100 m2 was used to measure diameter and height of trees. The results show that the diameter of trees in thinned stands was 19.98 cm and in the control stands 13.84 cm, while the mean heights were 18.33 and 17.46 m, respectively. The mean basal area in thinned stands was 30.74 m2 and in the control 15.70 m2 per ha. The results of Student＇s t tests indicate that there are significant differences at a probability level of 99.9% between the two variously treated stands in diameter （d）, height （h）, basal area, volume growth and the stabil- ity coefficient. We conclude that tending operations with suitable intensity in different time periods are recommended to obtain stable stands.     

Determination of fiber length and juvenile and mature wood zones in Acer velutinum Boiss. trees grown in Iran

In our investigation we studied fiber lengths and the transition age from juvenile to mature wood in Acer velutinum Boiss. For this purpose, samples from three normal maple trees at a Noshahr site in northern Iran were selected. Disks were cut at breast height. Test samples were taken along a radial direction from the pith to the bark, accounting for every ring during a 48-year period. We used the Franklin method to distinguish between fibers of juvenile and mature wood. The results show that the fiber length increased along the radial direction from the pith to the bark. The transition age between juvenile and mature wood was determined at the 14th annual ring from the pith.     

Effect of different seed treatments on dormancy breaking and germination in three species in arid and semi-arid lands

Seeds of many woody plant species have one of several types of dormancy. They do not germinate unless specific environmental signals are in place or events occur. This study was conducted to evaluate the effects of scarification treatments on seed dormancy and germination of Acacia nilotica (L.) Willd. ex Del., Prosopis juliflora (Sw.) DC. and Dodonaea viscosa (L.) Jacq. The following treatments were applied: T1, untreated seed (control); T2, sulphuric acid (97%) for 45 min; T3, boiling water for 5 min. The seeds were cultured on a Murashige and Skoog (MS) medium after sterilization. The responses of seeds to treatments were compared with each other and with the control treatment. Germination was observed daily for a 30-day period. Results indicated positive responses to treatments, while impermeable seed coats may be responsible for low germination rates in intact seeds as seen experimentally in the untreated control. The highest germination was obtained for P. juliflora and D. viscosa acid-scarified seeds (80.8%-90.8%) and for scarified seeds of A. nilotica (50.2%) boiled in water. The germination indices, i.e., final germination percentage (FG), mean daily germination (MDG) and germination rate (GR), were significantly affected by treatments and species (p<0.01).     

铝处理对茶条槭不同种源种子发芽指标的影响

以吉林市、大连市和尚志市3个种源的茶条槭种子作为试验材料,研究铝元素对茶条槭不同种源种子有关发芽指标的影响.结果表明:在3个铝质量浓度处理下,3个种源种子的胚轴长差异不明显;大连种源在2.0g·L-1铝质量浓度处理后种子发芽率和活力指数达到了最高,而尚志市种源在3.5g·L-1铝质量浓度处理后发芽率达到了最高;在5.0...     

Wood anatomical changes due to uptake of cadmium and lead from contaminated soils in Acer velutinum seedlings

We investigated wood anatomical changes due to uptake and accumulation of cadmium and lead from contaminated soils in Acer velutinum Boiss seedlings. Two-year old seedlings were exposed for 180 days to soil concentrations with varying cadmium and lead concentrations. We measured three wood anatomical traits, average vessel area(μm2), vessel number per square millimetre, and vessel lumen area percentage (%). For assessing the cadmium and lead accumulation, we measured the concentrations in the soil, leaf, stem, and root. Average vessel area and vessel lumen area percentage were similar (p>0.05) incontrol and treated seedlings. Vessel number per square millimetre showed a decreasing trend from pith to bark in control and treated seedlings, and the trend was more pronounced in treated seedlings. We conclude that vessel number per square millimetre in A. velutinum is influenced by soil contamination. A. velutinum Boiss is not a suitable species for remediation of soils contaminated by cadmium and lead but it can beused as an indicator of the soil lead contamination, because lead concentrations in seedlings increased with increasing amount of lead in the soil.     

Loblolly pine seed dormancy: constraints to germination.

Stratification by moist chilling is often used to break seed dormancy in loblolly pine (Pinus taeda L.). The role that moist chilling plays at the cellular level in preparing the embryo for germination and early seedling growth was investigated. Moist chilling did not affect the embryo's ability to mobilize seed storage proteins, which is a biochemical marker of early seedling growth. Analysis of in vivo protein synthesis profiles indicated that moist chilling has only a subtle effect on gene expression in the embryo or germinant. The means by which moist chilling affects interactions between the seed coat and the living tissues of the seed also was studied. Although the seed coat is mainly a mechanical barrier to germination, seed coat replacement studies showed that moist chilling alleviates some factor(s) in the seed coat that significantly inhibit germination.     

Variable dormancy in seed of Pinus contorta

Seeds of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) collected southwest of Grande Praire, Alberta at three different times and altitudes between August 20, 1984 and August 15, 1985 showed variable responses to stratification. The responses were related to seed ripeness, as judged through evaluations of cone moisture contents, and with the length of time that the cones had remained on the trees. Unripe seeds started to lose germination in the third year after pollination when on the tree. Mature seeds which lost germination by late fall 1984 regained it by the next fall, while most unripe seeds did not. Immature seeds increased their need for stratification over time while mature seeds did not. Seeds should be left on the tree until the end of the third year to insure maximum viability because they do not reach maturity until then.     

Abscisic acid and the regulation of embryo dormancy in the genus Acer

Germination of Acer pseudoplatanus L. and Acer platanoides L. seeds was increased by moist storage of the intact fruits (seed + pericarp) at 5 degrees C, but not at 17 degrees C. In both species, germinative capacity of isolated embryos (seeds with testa removed) was increased by moist storage of fruits at either 5 or 17 degrees C. Thus dormancy loss by intact seeds and excised embryos was not necessarily correlated. Loss of dormancy in isolated embryos was associated with a reduction in free abscisic acid (ABA) content. Embryos from freshly harvested fruits of A. pseudoplatanus had a higher germinative capacity and a lower free ABA content than embryos from freshly harvested fruits of A. platanoides. Morever, germinative capacity increased, and free ABA content decreased, more rapidly with length of fruit storage in A. platanoides embryos than in A. pseudoplatanus embryos.     

山楂种子呼吸代谢与休眠的关系

为了探讨山楂种子呼吸代谢与休眠的关系,将山楂种子层积处理一个冬季,测定层积前后呼吸代谢的变化。结果表明,山楂种子经层积处理后,细胞膜透性增加;G6PDH,MDH,CAT和SOD活性提高,呼吸加强;呼吸代谢以磷酸戊糖途径为主,酵解-三羧酸循环和无氧呼吸的总和变化不大,由非糖物质作为呼吸基质的比例显著增加。     

Breaking seed dormancy in European rowan seeds and its implications for regeneration

The effects of the presence of a medium, seed moisture content, warm and chilling treatments on the germination response of European rowan (Sorbus aucuparia L.) seeds of Irish origin were investigated with the aim of reducing precocious (or premature) germination and maximising germination after pretreatment. After adjusting seed moisture content, seeds of two lots were subjected to warm treatment for 0–6 weeks followed by 0–50 weeks of chilling. The seeds then were allowed to germinate at a constant 15 °C with 8 h lighting per day or 20 (dark)/30 °C (light). Some seeds were treated in the fully imbibed (FI) state in a medium (standard operational treatment). Seed lot effects were evident, but treatment effects were consistent in each lot. Warm treatment greatly increased germination and reduced precocious germination. The presence of a medium was not required to achieve high germination and seed moisture content close to the FI state was needed to maximise germination. Climate change may reduce the ability of this species to regenerate naturally, favouring other species that require less chilling.     

Breaking seed dormancy of Pinus bungeana Zucc. with Trichoderma-4030 inoculations

Seeds of Pinus bungeana are very dormant due to the impermeability of their seed coats. We have found that treatment with microorganisms (Trichoderma-4030) can effectively soften the seed coats, and thus promote germination. Further trials will be undertaken to confirm the practical application.     

Primary metabolite mobilization and hormonal regulation during seed dormancy release in Cornus japonica var. chinensis

The combination of gibberellin acid (GA) soaking with moist chilling plays a pivotal role in seed dormancy breaking. However, knowledge involving physiological and biochemical mechanisms for such a response is limited. This work focused on the effects of GA₃ and moist chilling on overcoming seed dormancy as well as the response of endogenous hormones and nutrient reserves to dormancy release in Chinese dogwood (Cornus kousa var. chinensis). Seeds subjected to GA₃ soaking and moist chilling exhibited a high germination percentage (average 97%), and the combination of 500 mg·L^?1 GA₃ soaking for 3 days followed with moist chilling for 50 days was more effective than other treatments. For GA₃ treatments, lipids were initially hydrolyzed during the first stage of moist chilling (0–20 days), resulting in the increase of starch and soluble sugars, while proteins were kept relatively stable. During the second stage (20–50 days), contents of lipids, starch, soluble sugars, and proteins decreased by 46%, 82%, 61% and 59%, respectively. Abscisic acid (ABA) contents and ratios of ABA to GA₃ in GA₃ treatments decreased by nearly 70% and over 90%, respectively, when dormancy was terminated. However, endogenous GA₃ contents in all treatments significantly increased with prolonged moist chilling. The present results provide insight into the metabolic mechanism involving hormonal regulation and mobilization of reserves during the release of seed dormancy in Chinese dogwood.     

濒危树种羊角槭种子基本生物学特征

采用种皮透水性测定、生活力测定、种皮和种胚甲醇提取液测定等方法,对羊角槭基本生物学特征进行了研究。结果表明:羊角槭种子呈压扁状卵圆形,由外种皮、内种皮、种胚和子叶组成,无胚乳;种子千粒质量50.88g,其中种皮占完整种子质量的79.55%以上;种子中空籽和败育种子比例达63.81%,反映出较高的种子败育率;饱满的种子中有生活力者占56.67%;种皮具有一定的透水性,种皮和种胚甲醇提取液对白菜籽发芽有抑制作用,说明羊角槭种子自身含有发芽抑制物可能是导致种子深休眠的主因。     

不同催芽方法破除青榨槭种子休眠的影响分析

针对青榨槭种子的休眠特性,采取低温层积和赤霉素处理两种催芽方法进行对比试验,分析研究破除青榨槭种子休眠的有效方法.结果表明,青榨槭种子经低温层积14d或500mg/LGA3浸种处理后,发芽指数和发芽率均达到最高,是打破青榨槭种子休眠的最佳方法.     

The structural and chemical characteristics of the pericarp are important in Tilia miqueliana seed dormancy

New Forests - Pericarp structure and permeability in Tilia miqueliana were explored using anatomy, paraffin section detection, scanning electron microscopy, and magnetic resonance imaging. The...     

Breaking seed dormancy in Cupressus atlantica Gaussen, an endemic and threatened coniferous tree in Morocco

Cupressus atlantica Gaussen (Cupressaceae) is an endemic and endangered coniferous tree geographically restricted to the N’Fis valley in South-Western Morocco. Like many forest species, C. atlantica exhibits dormancy which delays and reduces germination. To improveseed germination, different pre-treatments were conducted on C.atlantica seeds after storage for different periods (one, two and five years) including: scarification with sandy paper; soaking seeds in hot distilled water at 60℃and 80℃for 15 min and soaking seeds for 48 h in agibberellic acid (GA3) at 1,000 and 2,000 mg·L-1. Results showed that scarification with sandy paper increased the germination rate of Atlas cypress by up to 67%, indicating that the species possess essentially anexogenous dormancy (physical dormancy) due to the hard seed coat(hardseededness). Exogenous application of gibberellic acid (GA3) at1,000 mg·L-1 was also effective in breaking seed dormancy and germination induction. These two treatments induced faster speed germination expressed by low number of days to first germination (8 10days) and low values of mean germination times (MGT). However,germination rate, under any treatment, is greatly dependent on the year of seed collection. Seeds collected in year 2004 gave the highest value,suggesting that even after five years of storage, the germination capacity of C. atlantica seeds could remain high. This observation is very interesting in the exsitu conservation of such endemic and endangered species where the production of seeds is irregular over the years.     

Longevity of <Emphasis Type="Italic">Juniperus procera</Emphasis> seed lots under different storage conditions: implications for ex situ conservation in seed banks

Juniperus procera Endl. is economically important timber species, but its populations are extremely small and fragmented in its natural habitat, thus, calling for immediate ex situ conservation. Here we examined the effects of seed sources and storage temperature on the longevity of Juniperus procera seed lots through collection and preservation of seeds in seed banks. Seeds were collected from nine sites across the species natural distribution in Ethiopia and stored in four warehouses: modern cold room (5℃), mud house (15℃), concrete block house (17℃ or corrugated iron house (20℃) for 42 months. Every three months, a random sample of stored seeds were drawn and tested for germination. A highly significant variation (p < 0.01) in germination of stored seeds was observed among different storage environments, seed lots, and duration of storage. Over the storage period, seeds stored in the cold room had the highest mean percentage germination, followed by the mud house, corrugated house and blocket house. The cold room (41%) and the mud house (38%) maintained the same level of germination as the intitial germination of the seedlotds (42%). The variation in longevity of stored seeds was significnatly correlated with the initial germination of seed lots (r > 0.80; p < 0.01). Cold storage also resulted in enhancement of germination through its stratification effect that terminated the non-deepphysiological dormancy of juniper seeds. In conclusion, seed lots with good initial germination can be effectively stored in cold room (5℃) up to four years. In the absence of modern cold stores, mud houses can be used as a good alternative to store seeds at local level.     

Interaction between reactive oxygen species and hormones during the breaking of embryo dormancy in Sorbus pohuashanensis by exogenous nitric oxide

The breaking of dormancy mediated by reac-tive nitrogen species (RNS) is related to the accumulation of reactive oxygen species (ROS) in germinating embryos but...