Foliage influences forced convection heat transfer in conifer branches and buds

Conifer foliage structures affect branch and bud temperature by altering the development and convective resistance of the thermal boundary layer. This paper examines foliage effects on forced convection in branches and buds of Picea glauca (Moench) Voss and Pinus contorta Dougl. Ex. Loud., two species that represent the range of variation in foliage structure among conifers. Forced convection is characterized by a power law relating Nusselt (heat transfer) and Reynolds (boundary layer development) numbers. Data were collected in a laminar flow wind tunnel for free stream velocities of 0.16-6.95 m s(-1). Scaling parameters were compared against literature values for silver cast branch replicas, a bed of real foliage, cylinders, and tube banks. Foliage structures reduced Nusselt numbers (heat transfer) relative to cylinders, which are typically used to approximate leafless branches and buds. Significantly different scaling relationships were observed for all foliage structures considered. Forced convection scaling relationships varied with foliage structure. The scaling relationships reported here account for variation within populations of branches and buds and can be used to characterize forced convection in a forest canopy.     

高大乔木原位与离体叶片气体交换特征的比较——以三种环境下的青冈栎(Cyclobalanopsis glauca)为例

乔木由于个体高大,采用便携式仪器(如Li-6400)进行气体交换测定时的采样存在很多困难.研究了岩溶区、非岩溶区和盆栽等3种生境条件下的青冈栎植物叶片离体后的气体交换参数衰变特性并与活体状态进行比较,以确定叶片离体后仍能代表原位状态的最佳测定时间.叶片离开母体后,气孔短时内略微变大,然后逐渐关闭.不同条件下气孔的这种变化差异较大;蒸腾作用与气孔导度极显著线性相关,蒸腾作用受到气孔关闭的影响明显.离体叶片的蒸腾作用的大小与叶片的温度高低相一致.光合效率与气孔导度也呈显著相关,但相关程度较前者弱.不同温度条件下离体叶片的气体交换特征是不一样的,岩溶区高温加速了叶片的蒸腾速率,减少叶片组织自由含水量,导致水分胁迫的提前到来.温度越低离体叶片光合作用的衰减过程越慢.离体叶片的气体交换参数的在一定时间范围内的可靠性取决于叶片温度.在温度较低的时候(如20℃),离体叶片的可靠性20min以上,温度比较高(非岩溶区,温度约为32℃))的情况下,只有10min左右,而温度很高(岩溶区,叶温≥32℃)的情况下,这种可靠时间只有3～6min.     

桂林岩溶区青冈栎光合速率与环境因子关系初步研究

在自然条件下,对桂林岩溶区青冈栎光合速率与环境因子的关系研究表明,初夏季节青冈栎蒸腾速率日变化为"单峰"曲线,光合速率日变化为"双峰"型曲线,午间光合速率明显降低。青冈栎光合"午休"主要由气孔导度降低引起;通径分析表明,环境因子中空气相对湿度和空气温度对青冈栎光合速率直接影响最大;光合有效辐射对青冈栎光合速率直接影响不显著,而主要是通过其它因子间接影响光合速率。     

Ovule and gametophyte development in Nicotiana glauca Graham (Solanaceae)

Abstract

The development of ovule and megagametophyte is examined in Nicotiana glauca, using light microscopy. The ovules proved unitegmic, tenuinucellate and endothelial as in all the Solanaceae so far studied. The ovule primordia are of the three-zonate type. The integument, which is of dermal origin, is at first two-layered but later produces additional intermediate cells whose origin is not constant. The nucellus, whose initial curvature bears no relation to the origin of the integument, has, like other Solanaceae, a one or two-celled archesporium from which a single meiocyte develops. The gametophyte is confirmed to be bisporic in origin and its development follows the Allium type. Furthermore, the hypostase, which is rare in the family, is observed below the antipodal cells.     

Comparison of physiological responses of guard cell protoplasts of Nicotiana glauca isolated from leaves collected before dawn or at midday

We observed that guard cell protoplasts isolated from leaves collected at midday from Nicotiana glauca Graham (tree tobacco) did not give the same physiological responses to light as those isolated from leaves collected in early morning. Based on that observation, we attempted to determine whether there were significant differences between the physiological responses of guard cell protoplasts isolated from leaves collected before dawn (with closed stomata) and those isolated from leaves collected at midday (with open stomata). We isolated guard cell protoplasts from leaves collected before dawn and at midday and compared (1) rates of red and blue light-induced pH changes in weakly buffered media caused by changes in their metabolism, (2) their rates of oxygen consumption in darkness and oxygen evolution in light and (3) relative rates of decay of variable chlorophyll a fluorescence in their chloroplasts. Studies with the vital stain fluorescein diacetate failed to reveal any significant differences in the viabilities of protoplast preparations from leaves collected before dawn and at midday. Furthermore, protoplasts from leaves collected at these times swelled to similar extents in an osmotic medium containing 10 µM fusicoccin and 5 mM KCI. Nevertheless, rates of light-induced pH changes, rates of oxygen consumption and evolution and rates of decay of variable chlorophyll a fluorescence were all lower in preparations of guard cell protoplasts from leaves collected at midday than in preparations from leaves collected before dawn. Initial volumes of guard cell protoplasts isolated from leaves collected at midday were 150% of those of guard cell protoplasts isolated from leaves collected before dawn. We suggest that the differences in responses of guard cell protoplasts isolated from leaves collected before dawn and at midday may be caused by (1) nonoptimal isolation conditions for guard cell protoplasts prepared from leaves collected at midday, (2) the lower surface-to-volume ratio of guard cell protoplasts isolated from leaves collected at midday or (3) diurnal and/or circadian regulation of guard cell metabolism over the course of a day.     

温度和土壤含水量对青冈栎种子萌发的影响

运用直播法,研究应用人工气候箱控制温度和土壤含水量对野生青冈栎种子萌发和幼苗生长的影响。结果表明:在12h光照条件下,青冈栎种子在变温为10℃/15℃时,萌发率很低,仅为(12±12.29)%;变温为30℃/35℃时,萌发率达最大,为(81±13.7)%。土壤含水量为30%～40%时,萌发率为(79±15.9)%;土壤含水量为90%～100%时,萌发率为(56.67±19.36)%。青冈栎种子萌发呈现出迅速萌发和推迟萌发的特点;温度对青冈栎幼苗的苗高、叶长和叶宽影响显著,对幼苗的地径、叶片数量影响不显著。恒温下,不同梯度土壤含水量处理对幼苗的苗高、地径、叶长、宽影响不显著。     

Biosynthesis stimulation of nor‐secotriterpene anxiolytics in cell suspension cultures of Galphimia glauca Cav

Galphimia glauca produces compounds denominated galphimines (galphimine‐A, galphimine‐B and galphimine‐E). Due to their important anxiolytic activity, we initiated in vitro cultures of the species with the purpose of developing a biotechnological process for obtaining galphimines. In this work, we stimulated the biosynthesis and excretion of galphimines with two‐phase batch‐type cell suspension cultures of G. glauca. The effect of nutritional variation and the 2,4‐dichlorophenoxy acetic acid added to Murashige & Skoog(MS) culture medium was evaluated. Later, we evaluated the effect of the stimulation with calcium and methyl jasmonate (MeJ). The greatest production of galphimine‐B (3.39 × 10^?5 g/L day^?1) was obtained on day 40 of kinetics, and induced by a treatment containing concentrations of nitrates and phosphate that are double of those normally used in MS medium, without sucrose but with added 2,4‐dichlorophenoxy acetic acid (4 mg/L). Time of galphimine‐B biosynthesis diminished due to the effect of MeJ in combination with calcium, and induced the excretion (100%) of galphimine‐B (6.35 × 10^?5 g/L day^?1) into the culture medium. Thus, the use of calcium and MeJ comprises a viable alternative to stimulate the production and excretion of galphimine‐B and galphimine‐A in batch‐type cultures of G. glauca in modified MS medium. Once optimized, the production of the anxiolytic compounds can be scaled up to the industrial level.     

滇青冈和高山栲种子昆虫寄生及其对种群更新的影响

对昆明西山地区滇青冈(Cyclobalanopsis glaucoides)和高山栲(Castanopsis delavayi)种子(坚果)虫蛀率在两个年份、整个落种期和山坡不同部位的变化情况进行研究,结果表明：① 寄生于滇青冈种子内的象甲为青冈象(Curculio megadens)和Curculio sp.,寄生于高山栲种子内的象甲是Curculio sp.和剪枝象(Cyllorhynchites sp.);② 滇青冈样地的虫蛀率为2484%~2760%,样地间无显著差异,两年间的平均虫蛀率亦无显著差异;高山栲样地间虫蛀率为1794%~2655%,有显著差异性,两年间的平均虫蛀率也有显著差异。③ 高山栲的下落种子虫蛀率随时间逐步下降,9月和10月中下旬出现两个虫蛀率的高峰期;高山栲种子内寄生的昆虫落地后即入土化蛹,滇青冈落地种子内的寄生昆虫在初期会滞留一段时间;④ 虫蛀率与林下实生苗数量无显著相关性,实生苗多集中在大树周围以及草本层植物较丰富的小生境。     

Metabolic engineering of ketocarotenoid biosynthesis in leaves and flowers of tobacco species

Ketocarotenoids and especially astaxanthin are high-valued pigments used as feed additives. Conventionally, they are provided by chemical synthesis. Their biological production is a promising alternative. For the development of a plant production system, Nicotiana glauca, a species with carotenoid-containing yellow pigmented flower petals, was transformed with a cyanobacterial ketolase gene. The resulting plants accumulated 4-ketozeaxantin (adinoxanthin), which is the first ketocarotenoid synthesized in flower petals by genetic modification. Due to the very late flowering in this tobacco species, N. tabacum was used to optimize the yield and ketocarotenoid product pattern by metabolic engineering of the ketolation steps of carotenogenesis. The highly carotenogenic nectary tissue in the flowers represents a model of a flower chromoplast system. By expression of a ketolase gene, it was possible to engineer the biosynthetic pathway towards the formation of 3'-hydroxyechinenone, 3-hydroxyechinenone, 4-ketozeaxanthin, 4-ketozeaxanthin esters, 4-ketolutein and 4-ketolutein esters. Some of these ketocarotenoids were also formed in the leaves of the trangenic plants. In particular, by co-expression of the ketolase gene in combination with a hydroxylase gene under an ubiquitous promoter, the formation of total carotenoids in nectaries increased by more than 2.5-fold. In the nectaries of this type of transformants, more than 50% of the accumulating carotenoids were keto derivatives. In addition, the levels of ketocarotenoid esters were much lower and a higher percentage of the free ketocarotenoids accumulated. These results open new promising perspectives for a successful metabolic engineering of keto-hydroxy carotenoid production in carotenogenic flowers.