The effects of seed size, cotyledon reserves, and herbivory on seedling survival and growth in Quercus rugosa and Q. laurina (Fagaceae)

In a greenhouse experiment, seedling survival of two oak species (Quercus rugosa and Q. laurina) was greatly affected by the excision of cotyledons 1 mo after germination, with a greater impact on Q. laurina. The effect of seed size was also significant for both species, with a positive correlation between seed mass and survival and growth. The effect of cotyledon excision on seedling growth persisted throughout the first growing season in Q. rugosa and was not analyzed for Q. laurina due to the low number of seedlings that survived cotyledon excision. Seed size significantly affected seedling height, diameter, leaf area, and biomass at 6 mo. Seed size and cotyledon retention affected the ability of Q. rugosa to recover from herbivory, as both factors had a significant effect on relative growth rates after aerial biomass removal. The results show that seedlings originating from large seeds can better endure loss of cotyledons and aerial biomass and thus are better equipped to confront stress early in their lives.     

Different vulnerabilities of Quercus ilex L. to freeze- and summer drought-induced xylem embolism: an ecological interpretation

Quercus ilex L. growing in the southern Mediterranean Basin region is exposed to xylem embolism induced by both winter freezing and summer drought. The distribution of the species in Sicily could be explained in terms of the different vulnerability to embolism of its xylem conduits. Naturally occurring climatic conditions were simulated by: (1) maintaining plants for 3h at ambient temperatures of 0, -1.5, -2.5, -5.0 and -11°C; and (2) allowing plants to dry out to ratios of their minimum diurnal leaf water potentials (Ψ₁) to that at the turgor loss point (Ψ_tlp) of 0.6, 0.9, 1.05, 1.20 and 1.33. The loss of hydraulic conductivity of one-year-old twigs reached 40% at -1.5°C and at Ψ₁/Ψ_tlP= 1.05. Recovery from these strains was almost complete 24 h after the release of thermal stress or after one irrigation, respectively. More severe stresses reduced recovery consistently. The percentages of xylem conduits embolized following application of the two stresses, were positively related to xylem conduit diameter. The capability of the xylem conduits to recover from stress was positively related to the conduit diameter in plants subjected to summer drought, but not in the plants subjected to winter freezing stress. The ecological significance of the different vulnerabilities to embolism of xylem conduits under naturally occurring climatic conditions is discussed.     

Rapid appearance of 13C in biogenic isoprene when 13CO2 is fed to intact leaves

Biogenic isoprene substantially affects atmospheric chemistry, but it is not known how or why many plants, especially trees, make isoprene. We fed ¹³CO₂ to leaves of Quercus rubra and monitored the incorporation of ¹³C into isoprene by mass spectrometry. After feeding ¹³CO₂ for 9 min we found all possible labelling patterns from completely unlabelled to fully labelled isoprene. By 18 min, 84% of the carbon atoms in isoprene were ¹³C. Labelling of the last 20% of the carbon atoms was much slower than labelling of the first 80%. The rate of labelling of isoprene was similar to that reported for phosphoglyceric acid indicating that there is a close linkage between the carbon source for isoprene synthesis and the photosynthetic carbon reduction pathway.     

栎链蚧属分类地位讨论及一新种记述：同翅目：蚧总科：链蚧科

栎链蚧属(Asterodiaspis)是专性寄生于壳斗科(Fagacea)植物的特有类群之一,部分种类的雌成虫寄生于同一寄主的不同部位(茎干、叶片)时,在形态上表现出一定的差异,从而表现为食干型(stem-form)和食叶型(leaf-form)的分化,这种生态二型现象(ecologieal dimorphism)表现出本类群的复杂多样性。本文在新种双型栎链蚧A.biformis sp.nov.形态记述的基础上,认为新栎链蚧属Neoasterodiaspis Borchsenius,     

γ-Glutamylwillardiine and γ-glutamylphenylalanylwillardiine from seeds of Fagus silvatica

γ-l-Glutamyl-l-willardiine [γ-l-glutamyl-3-(1-uracil)-l-l-alanine] and γ-glutamylphenylalanylwillardiine have been isolated from seeds of Fagus silvatica. The structures have been established by spectroscopy, hydrolysis to give the constituent amino acids, and for the tripeptide end-group determination and partial hydrolysis to give the two constituent dipeptides.     

Lipids of oak galls

The nutrient tissues of oak galls accumulate a great amount of lipids. The neutral lipids (essentially triacylglycerol) are the most abundant storage form but some membrane lipids (mainly phospholipids) also occur. However, the galactolipids are very poorly represented. Among the fatty acids, oleic acid is predominant. These data correlate well with the cytological features of gall nutrient cells.     

中国芸香科及壳斗科植物资料

<正> 芸香科 Rutaceae 酒饼簕属 Atalantia Correa 薄皮酒饼簕 Atalantia henryi (Swingle) Huang, comb. nov. Atalantia racemosa Wight et Arn. var. henryi Swingle in Journ. Arn. Arb. 21:127, 1. 4, Pf. 1—4,1940 et in Webb. et Batc. Citrus Indust. 1:329. 1948; Huang in Acta Phytotax. Sin. 8:115. 1959.