Utilization of nitrogen from storage and current-year uptake in walnut spurs during the spring flush of growth

[¹⁵N]-depleted (NH₄)₂SO₄ applied to the soil in 1985 resulted in residual labeling of about 16% of the storage nitrogen (N) pool of mature walnut ( Juglans regia L. cv. Serr) trees in 1987. Application of [¹⁵N]-depleted (NH₄)₂SO₄ fertilizer to a different set of mature walnut trees in 1987 allowed monitoring of the kinetics and utilization of N from current year uptake in 1987 and resulted in >20% labeling of fruit N following completion of leaf expansion. Redistribution of storage N to the new growth predominated during the spring flush of growth although N derived from the soil during current-year uptake contributed increasingly during leaf expansion. Labeled N from current year uptake accumulated preferentially in the leaves as compared with reproductive organs during leaf expansion but subsequent to leaf expansion, fruit were more highly labeled with N derived from current-year uptake than leaves. Pistillate flower abortion was coincident with an apparent competition for N among developing vegetative and reproductive organs and preceded the period of significant N contribution from current-year uptake.     

三种正常与矮化植物的木材比较观察

本文比较观察了三种不同木材类型的正常与矮化树木的木材结构:针叶材的太白红杉(Larix chinensis Beissn.)、散孔材的辽东桤木(Alnus sibirica Fisch.)和环孔材的蒙古栎(Quercus mongolica Fisch.)。这些植物在个体发育过程中,各年的年轮宽度及管状分子长度、宽度等变化,存在各自的规律性。这些规律并不因生长环境的差异而变更。不过,逆境下生长的矮化植株的年轮宽度和管状分子的大小明显地比正常的要窄小,同时在木材结构的其它数量性状上,也有较大变化;然而,其各自的种属定性特征仍保持稳定。这些似乎可说明:生态环境的变化对木材结构的数量性状有较大影响,但是对木材种属的定性特征则无明显作用。     

树鼩(Tupaia belangeri chinensis)耳蜗毛细胞铺片的观察

我们用树鼩14只,取耳蜗铺片后进行毛细胞计数和长度测量。发现树鼩毛细胞数及缺失率与人、猴、豚鼠不同,树鼩毛细胞失数少且稳定,蜗尖弃用部少,不同种群间的个体差异小,利于用作生物学实验动物,可为研究耳的生理、病理及临床服务。     

In vitro nodulation of micropropagated plants ofLeucaena leucocephala byRhizobium

Micropropagated plants ofLeucaena leucocephala nodulated with Rhizobium during thein vitro hardening stage, grew well on N-free-substrate. This is the first report ofin vitro nodulation of micropropagated plants by Rhizobium.     

The role of remnant forest trees in tropical secondary succession

This paper emphasizes the contribution of remnant trees to the establishment of woody species during succession on abandoned fields and pastures in the Mexican rain forest area, Los Tuxtlas, Veracruz. Remnant trees, original large forest trees left in the clearings by traditional farmers will become natural perching sites for both passing and resident birds. Frugivorous birds drop or regurgitate seeds and fruits which fall under the canopies of remnant trees during their stay, thus contributing to an accumulation of species, which make these remnant trees into ‘regeneration nuclei’. The species transported into these sites belong chiefly to older stages of successional development and reach these otherwise isolated areas, counteracting the depauperization of tropical land, brought about by both intensive and extensive clearing. In a study of seven remnant trees, 29 woody species and two climbers were found, 86% of which are bird dispersed. The total number of species per tree varied from 6 to 15 and was higher under remnant trees with fruits attractive to birds. Floristic variations of the understorey as detected by detrended correspondence analysis was correlated with the relative amount of shade-tolerant primary and late secondary trees versus light dependent pioneers and early successional trees.     

A method for measuring radial differences in water content of intact tree stems by attenuation of gamma radiation

Abstract. A technique is described for the nondestructive measurement of water content variations in the stems of trees.
The density of intact tree stems in the forest was estimated using attenuation of gamma radiation. Water content was calculated after subsequent derivation of the volume fraction of solid matrix.
A radial sequence of such measurements was obtained by measuring a sequence of chords, and assuming homogeneity within concentric tori. Analysis of the source of errors showed that the system was a close approximation of an ideal, rigid-geometry, mono-energetic source/detector system, with basic precision dependent on the quantity of gamma radiation measured. Correlation coefficients between the gamma-attenuation technique and subsequent gravimetric estimates of water content for two field experiments reported here were 0.882 and 0.938.
The technique was shown to be capable of describing the radial and diurnal variation in water content at two heights in the stem of a 20-year-old tree of Pinus contorta .     

Modification of pH of latex cytoplasm by ethylene

In the absence of glycolytic activity the pH of isolated latex cytoplasm of Hevea brasiliensis increases progressively during the first hours of incubation. This increase is greatly enhanced after bark treatment with 2-chloroethylphosphonic acid. The process of alkalization is not enzymic and is oxygen dependent. This observation is discussed in relation to the increase in latex pH in situ under hormone action.     

A review on the effects of nitrogen and phosphorus addition on tree growth and productivity in forest ecosystems

Nitrogen (N) and phosphorus (P) inputs induced by anthropogenic activities and atmospheric N and P deposition have largely increased the availability of soil N and P in terrestrial ecosystems, which have considerably affected terrestrial carbon cycling processes. Tree growth and productivity in forest ecosystems play an important role in global carbon cycling, and determine the magnitude and direction of terrestrial carbon sequestration. Currently, a large number of field manipulation experiments have been conducted to investigate the effects of N and/or P addition on tree growth and forest productivity, but the results from these studies were inconsistent. Such inconsistent results might be affected by multiple factors, including biological, environmental and experimental variables. Here, we reviewed the present research status of the effects of N and P addition on tree growth and forest productivity in forest ecosystems based on three aspects, including the number of publications and experiments with field N and P addition, and the global distributions of these experiments. Then, we summarized the methods for assessing tree growth and forest productivity at ecosystem level in forest ecosystems, including relative growth rate and absolute increment. According to the related results, we reviewed the regulating factors that affect tree growth and productivity, and the potential mechanisms for such factors, including climate, tree size and stand age, plant functional traits (including type of tree-associated mycorrhizal fungi, N-fixation property of trees, and conservative and acquisitive functional traits), plant-microbe interaction, ambient nutrient (i.e., N and P) deposition rate, and experimental variables. Finally, we summarized the current studies, and pointed out five aspects that are urgently needed to provide further insights in future studies, including the physiological mechanism of how tree growth responds to N and P addition, the tradeoff and allocation among growth of various parts of tree under N and P addition, the role of plant functional traits in regulating and predicting the responses of tree growth to N and P addition, how the competition among trees regulates the responses of tree growth to N and P addition, and conducting long-term and coordinated distributed field experiments investigating the effects of N and P addition on tree growth and forest productivity at the global scale.     

Comparative recruitment patterns of two non-pioneer canopy tree species in French Guiana

Summary A comparative study was conducted on the recruitment patterns of two non-pioneer tree species, one dispersed by arboreal mammals and birds (Virola michelii, Myristicaceae) and the other by rodents (Moronobea coccinea, Clusiaceae). These species differ in fruiting phenology, seed size, dispersal distance, germination time and seed nutrient exhaustion. In both species, establishment patterns were consistent with the escape hypothesis and the Janzen-Connell model. Virola seeds need not be buried to survive and germinate, and may produce a seedling carpet beneath the parent. Moronobea seedlings only establish from seeds buried by scatterhoarding rodents in the surrounding understory. One-year survival of Virola seedlings was 47.8% and was greater >10 m than < 10 m from the largest parent tree. In contrast, survival of Moronobea seedlings was 56% 3 years after seed dispersal. Survival of juveniles was greater in gaps than in the understory for Virola but not for Moronobea. Moronobea survival was greater than Virola survival in both microhabitats. Both species establish in the understory, yet both grew faster in gaps. Virola appeared to be more gap-dependent than Moronobea which may persist several years in the understory until a gap occurs. Virola and Moronobea illustrate two intermediate recruitment patterns along an hypothetical continuum of nonpioneer species replacement (Bazzaz and Pickett 1980; Swaine and Whitmore 1988).