植物剪枝蒸腾速率变化规律的初步研究

通过对毛乌素沙地几种主要植物的枝条在剪断前后的蒸腾速率的研究 ,发现这些植物枝条的蒸腾速率在剪离母株后一般会发生较大的变化 ,说明用快速称重法测定得到的剪断枝条的蒸腾速率与剪断前植物的实际蒸腾速率也存在较大的偏差。由于这类变化与植物的生物学特性、生长环境的水分条件、测定时叶片的水分状况、剪断的部位和测定的时间等多种因素都有密切关系 ,定量地预测某个植物剪断枝条的蒸腾速率的变化一般也比较困难。用快速称重法测定植物的蒸腾速率需要有同步的校正措施 ,否则结果不可靠。气孔计在测定植物枝条剪断前后蒸腾速率的相对变化率时比较准确。因而 ,用快速称重法测定植物的蒸腾速率 ,用气孔计来校正其偏差 ,这种二合一的方法是测定植物蒸腾速率比较准确而理想的方法     

中国越桔属的研究

本文讨论了越桔属在杜鹃花科中的系统位置;报道了国产越桔属的已知种91种,归为15个组级类群,按组可划分为5个分布区类型;指出了本属植物在形态、习性上的变异趋向;并联系越桔亚科的分类与分布,讨论了本属区系起源问题,作出几点初步推论: 1.越桔亚科的基干类群极可能发源于古南大陆西北部,也即热带美洲位置偏北。 2.越桔属的原始类群是古南大陆西部山地区系的后裔,而不是从东亚起源。在南、北古陆接触的热带东南亚繁衍后,经中南半岛至我国西南、南部、东部渗入到中部,而后往北。 3.对本属温带成分的13个组的区系分析,认为北温带成分的根源是在热带高山,而北极-高山成分的越桔,来源于亚洲、美洲的亚热带、热带山地     

EMBRYONIC GENETIC LOAD IN THE HIGHBUSH BLUEBERRY,VACCINIUM CORYMBOSUM (ERICACEAE)

Hand-pollinations of 28 autotetraploid V. corymbosum accessions from a single population resulted in lower self- than outcross seed set. Fertility varied widely, ranging from clones that were effectively female sterile to individuals with high seed yields in both matings. Self- and outcross fertility were highly correlated. A genetic load model was invoked to explain these phenomena. Reduced self-fertility was attributed to homozygosity for sublethal mutations at loci controlling embryo development, or to loss of heterotic interactions at these loci. Near zero cross-fertility in some clones may be evidence of partially dominant mutational load. Estimates of the number of lethal equivalents per zygote carried by individuals in this population ranged from 2.2 to 20.4, with a mean of 9.6. Embryonic genetic load at the individual level was significantly correlated with heterozygosity at nine enzyme loci. Low pollen viability and reduced receptivity to pollen from any source were also noted in the low fertility genotypes. It is suggested that gametic, gametophytic, and embryonic development are symptomatic of the amount of genetic load carried by individuals.     

FRUIT RIPENING ASYNCHRONY IS RELATED TO VARIABLE SEED NUMBER IN AMELANCHIER AND VACCINIUM

Two vertebrate-dispersed woody plants, Vaccinium corymbosum and Amelanchier arborea, were studied in southeastern Michigan to determine the proximate causes of their within-plant fruit ripening asynchrony. Individual flowers were followed from opening (A. arborea) or fruit initiation (V. corymbosum) to fruit ripening. Fifty-nine to 100% of the variance in fruit-ripening dates within V. corymbosum plants was due to variance in the development time; little was due to variance in initiation dates or covariance between these two terms. Similarly, 98% of the variance in fruit-ripening dates in A. arborea was due to variance in the number of days from flower opening to fruit ripening. Fruit developmental time in V. corymbosum and flower-fruit interval in A. arborea were significantly correlated with seed number: fruits with more seeds developed faster. I hypothesize that in both species ripening asynchrony is largely a consequence of variability in seed number.