EFFECTS OF PHOTOPERIOD AND GIBBERELLIN ON THE GERMINATION OF SEEDS OF BEGONIA EVANSIANA ANDR.

1. Seed germination of Begonia Evansiana ANDR. was investigatedat 29?C.
2. The germination was induced under long-day conditions,the criticaldaylength being about 8 hours. Exposure to at least2 or 3 cyclesof long days was necessary for germination. Theseeds couldgerminate under otherwise non-inductive photoperiods,when thedark period was interrupted with a short period ofillumination.Thus the photoperiodic behaviour of Begonia seedsin germinationis similar to that of typical long-day plantsin flowering.
3. The application of gibberellin brought aboutno germinationin complete darkness, but markedly reduced thecritical daylengthfor germination, even 1-minute photoperiodsbeing inductive.The germination under continuous light wasalso favoured bygibberellin application. The action of gibberellinin germinationof Begonia seeds may be to intensify the lightaction or tosubstitute for a part of it.

¹Present address: Dept. of Botany, Hokkaido University, Sapporo. (Received October 19, 1959; )     

A portable integrated automatic apparatus for the real-time monitoring of bioluminescence in plants

Real-time monitoring of gene expression by a bioluminescence reporter gene is a powerful method for large-scale, detailed analysis of gene expression in living cells and large-scale screening of mutants. We have developed a portable, compact, integrated automatic bioluminescence-monitoring apparatus that can continuously monitor 960 individual plant seedlings or micro-organism colonies under uniform light conditions at temperatures up to 50 °C. The apparatus gave reproducible and reliable results for both bioluminescence photon counts and period length of bioluminescence rhythms of Arabidopsis reporter strain. Using the apparatus, we measured bioluminescence rhythms in the thermophilic cyanobacterium Thermosynechococcus at temperature up to 43 °C. We also monitored the expression of the flowering regulator gene CONSTANS in Arabidopsis as bioluminescence in high time resolution under different photoperiodic conditions. The high-throughput bioluminescence-monitoring apparatus developed here is a powerful tool for real-time monitoring of gene expression and gene function.     

Strophiole of seeds of the black locust acts as a water gap

In Japan the black locust (Robinia pseudoacacia L.) is undergoing rapid habitat expansion, which has an adverse effect on native vegetation. It is therefore a priority to clarify the regeneration characteristics of the black locust and establish adequate management of this invasive species in Japan. To determine the germination characteristics of physically dormant black locust seeds, we observed anatomical features of the seed coat and identified the water gap that acts as a signal detector. Our microscopic observations showed that seed coats of this species had hilum, micropyle and strophiole. The anatomical features of these regions correspond to the general characteristics of papilionoid legume seeds. Based on our microscopic observations, water absorption blocking experiments and a dye tracking experiment, we identified the strophiole as a water gap in black locust seeds. Our results suggest that the opening of the strophiole is important for water uptake to the embryo and subsequent germination of black locust seeds under natural conditions.     

中国东北地区兴安落叶松林树干呼吸的研究

树干呼吸是森林碳平衡估计中的一个重要项目同时还能够显示树木的活力.对于如何准确估计森林树干呼吸释放CO2总量还存在争论.在本项研究中,2001～2002连续两年在一个33年生的兴安落叶松(Larix gmelini Rupr.)人工林内对树干呼吸进行了测定,同时测定了不同高度树干呼吸、呼吸的日变化、同龄落叶松林内不同个体的树干呼吸以及相关生长状态因子、水分因子和温度因子.结果显示:1)树干上部的呼吸速率在不同季节都高于下部呼吸速率,树干温度的差异能够一定程度上解释这种差异;2)树干呼吸有午间降低的现象,上午的测定结果树干温度与树干呼吸速率紧密相关,而下午则温度依赖性很小,土壤、空气、小枝木质部水势、叶片蒸腾速率和气孔导度都显示下午植物水分亏缺下午较上午严重,呼吸的这种上下午温度相关性的差异可能受这种水分亏缺的影响;3)在同龄林内,树木个体生长状态包括平均生长速率和树冠投影面积与树干呼吸速率有显著相关关系,而树干温度与之相关性很小.幂指数模型和S曲线模型能够产生较好的拟合效果;4)树干呼吸季节变化明显,7月份出现最大值,但同一月份的年间差异较大.自然指数模型能够较好地拟合温度与树干呼吸的季节变化规律.Q10值在2.22(2001年)和3.53(2002年)之间,与以往研究的结果相当.从以上结果可以看出,通过单一的Q10值估计森林树干呼吸总量会产生偏差,要想得到准确的估计,至少应该考虑生长状态的差异和水分状态的差异.     

林木非同化器官与土壤呼吸的温度系数Q10值的特征分析

温度系数(Q₁₀,温度每变化10 ℃,呼吸速率的相对变化)不仅可以用来描述不同森林非同化器官(根系和树干)和土壤对温度升高的敏感性,并由此断定它们在全球变暖进程中的不同表现,而且是其呼吸总量定量估计中必不可少的参数。虽然目前已经进行了大量的研究,但不同研究者结论并不一致,影响我们对问题的整体把握。因此,有必要综合以往文献进行统计分析。该文综合大量文献,评述了林木非同化器官和土壤的Q₁₀值频率分布、不同研究方法对Q₁₀值的可能影响并探讨了它们对温度升高的敏感性。结果表明,不同非同化器官和土壤的Q₁₀值差异较大,但具有相对稳定的分布中心范围。其中,土壤呼吸Q₁₀值中,频率分布最集中的区域是2.0~2.5,占23%,其中超过80%的测定结果在1.0~4.0之间,中位数为2.74。 根系呼吸的Q₁₀值,频率分布最集中的区域2.5~3.0,占33%,而大部分(>80%)的研究结果在1.5~3.0之间,中位数为2.40。树干呼吸的Q₁₀值中,频率分布最集中的区域是1.5~2.0,占42%,而90%以上的测定结果在1.0~3.0之间,中位数为1.91。通过对比,发现不同非同化器官Q₁₀值不同(树干<根系<根系与土壤共同体<去除根系土壤)。其中树干和根系的Q₁₀值显著低于去除根系土壤的Q₁₀值(p<0.05),表明土壤微生物活动对于未来全球变暖的反应要比木质化器官更敏感。此外,常绿植物的根系和树干呼吸的Q₁₀值与落叶树木对应值差异不显著,说明同化器官叶片的着生时间长短对非同化器官Q₁₀的影响不大。不同的CO₂分析方法(碱吸收法,红外线测定技术和气相色谱方法)对土壤呼吸Q₁₀值测定结果的影响不显著(p>0.10),根系分离方法(断根测定和壕沟隔断测定)也对根系呼吸的Q₁₀值影响也不显著(p>0.10)。但是,与活体测定相比,离体测定树干呼吸显著提高了其Q₁₀值。总体来看,不同林分相同非同化器官以及不同非同化器官呼吸的Q₁₀值相对稳定但仍具有较大的差异性,研究方法也对结果产生一定影响,在进行呼吸总量的定量估计中应该注意这一点。今后研究的重点是进一步把影响森林非同化器官呼吸的外在因素和内在因素综合考虑于Q₁₀值相关模型中,以便准确定量估计其呼吸总量,而研究难点是深入研究Q₁₀值具有较大变异性的原因(如温度适应性)和内在机理以便更好的表征不同器官和生态系统组分对全球变暖的敏感性。     

Depth distribution of three Typha species, Typha orientalis Presl, Typha angustifolia L. and Typha latifolia L., in an artificial pond

The depth distribution of the aquatic macrophyte Typha orientalis Presl was examined in comparison with two other Typha species: Typha angustifolia L. and Typha latifolia L. Vegetation surveys mapping the depth distributions were conducted at Ushigafuchi Pond, Tokyo, Japan, in autumn 2004 and 2005. All vegetation had been cleared from this artificial pond in spring 2003. In 2004 T. orientalis was distributed in shallow to deep water habitats between T. latifolia (shallow water regions) and T. angustifolia (shallow to deep water regions). However, by 2005 T. orientalis had almost disappeared from the pond. It had been replaced by Leersia japonica Makino at depths of 0–30 cm, by Schoenoplectus validus (Vahl) at depths of 30–60 cm and by T. angustifolia at depths of 60–100 cm. It appears that T. orientalis is not a strong competitor, particularly with taller species, but rather a pioneer species.