MATERNAL INVESTMENT AND FRUIT ABORTION IN PHASEOLUS VULGARIS

Plants lose some of their parental investment through fruit abortion. Resource conservation theory predicts that the maternal plant should abort those fruits furthest from maturity in order to conserve scarce resources. Embryo-quality theory predicts that the maternal plant should favor offspring of particular genotypes. I recorded the patterns of maternal investment in floral cohorts of domesticated and wild beans, Phaseolus vulgaris L. In accord with the resource conservation theory, late pod cohorts have the highest fruit abortion rates. When domesticated beans are grown in smaller pots, late cohort survivorship declines. When domesticated beans are crossed with pollen donors of different degrees of relatedness, the fruit abortion rate is the same even though seeds from the outbred crosses weigh more. The challenge for ecologists is to model and test the combined and possibly conflicting effects of selection for resource conservation and high offspring quality.     

LEAF DEVELOPMENT OF PHASEOLUS VULGARIS L. IN LIGHT AND IN DARKNESS

Development of the primary bean leaf in the dark and under continuous white light was studied during 14 days after sowing. The increase in surface area of the blade is the result of a number of sequential processes. Both in the darkness and under illumination, leaf growth is characterized by an initial cell enlargement followed by intensive cell division. Cell division in etiolated leaves continues for one day longer than in illuminated ones, but it proceeds at a slower rate. Mature leaves grown under white light undergo a phase of cell enlargement after cell division has stopped. This increases their surface area up to 800 times when compared with the blade area of the embryo. This enlargement phase is almost absent in dark-grown seedlings. Consequently the blade area of etiolated leaves is only 50 times that of the embryonic state. Thus light appears to have a dual effect on leaf development: it activates cell division and induces cell expansion.     

矮生菜豆胚乳细胞形成时的超微结构研究

应用透射电镜对矮生菜豆的游离核胚乳、胚乳细胞及珠被绒毡层的超微结构进行了观察,揭示了胚乳细胞化过程中自由生长壁的形成方式。实验表明,在游离核胚乳中存在大量有被小泡,胚乳游离核的外层核膜发生明显外突并以出芽的方式产生有被小泡。初始胚乳细胞壁为自由生长壁,大量有被小泡融合于自由生长壁末端使之不断延伸并产生分枝。与珠被绒毡层相邻的胚乳细胞产生发达的壁内突,具有传递细胞特征;在这些细胞中出现大量的核糖体及粗糙内质网,表现现高度的合成活性。     

菜豆胚乳游离核中的线粒体(简报)

在植物细胞中,细胞核以及具DNA的细胞器——质体和线粒体,在结构上通常各具自身的被膜而独立存在。关于核与这两种细胞器以及两种细胞器之间通过外膜的连接在一些植物中已有报道。最近,Yu和Russell在烟草中发现了细胞核中存在线粒体的现象。本     

WITHIN- AND AMONG-TREE VARIATION IN FLOWER AND FRUIT PRODUCTION IN TWO SPECIES OF CARYA (JUGLANDACEAE)

The patterns of variability in the production of staminate inflorescences, pistillate flowers, and fruits for Carya ovata (Mill.) K. Koch and C. tomentosa (Poir.) Nutt. at Hutcheson Memorial Forest (Somerset County, New Jersey) were examined over a four-year period. We sought to determine 1) the patterns of variability in flowering and fruiting (within-trees, among-trees, and between-years), 2) if variable flowering might account for observed nut-bearing patterns, and 3) what were the relative contributions of intrinsic (genetic) and/or extrinsic (environmental) factors in determining flower production and fruit set. In general, our fine-scale analysis of shoots within canopies did not reveal a distinct mast fruiting pattern. While the number of male and female flowers varied significantly (among trees and between years), fruit set was not markedly affected. Variability of flowering and fruiting among shoots within trees was low. Both flowering and fruiting were observed to have a strong genetic and/or microenvironmental basis; however, flowering appeared more plastic and thus more sensitive to yearly environmental vagaries than did fruiting. Favorable environmental conditions at the time of flower differentiation may result in increased flower production; but, this does not necessarily result in increased fruit set. Many pistillate flowers abscise around the time of pollination and fertilization, apparently adjusting fruit set to available shoot resources. Approximately 50% of the pistillate flowers of both species fail to set fruit. Overall, individual trees exhibit their own flowering and fruiting schedules, suggesting the need to account for this level of variability in future studies of mast fruiting.     

THE EFFECT OF BORON DEFICIENCY ON CALLOSE FORMATION AND 14C TRANSLOCATION IN BEAN (PHASEOLUS VULGARIS L.) AND COTTON (GOSSYPIUM HIRSUTUM L.)

Callose accumulated in the tissues of boron deficient bean and cotton plants, the extent and distribution of which depended on the species. Sieve plates in the phloem of boron deficient bean were characterized by heavy plugs of callose, while the sieve plates of boron deficient cotton were essentially unaffected. Translocation of ¹⁴C was, however, drastically reduced in both plants. It is suggested that callose deposition in boron deficient plants is a secondary effect of cellular damage.     

THE INTERACTION OF AUXIN AND ETHYLENE IN THE MAINTENANCE OF LEAF BLADE FORM IN PHASEOLUS VULGARIS L. VAR. PINTO

Auxin treatment results in hyponastic curvature of the primary leaves of Phaseolus vulgaris L. var pinto. Ethylene production by hyponastic leaves is detected within 1 hr after treatment with IAA in concentrations at or above 1 μm. The amount of ethylene detected is proportional to the concentration of auxin applied. Untreated control leaves and leaves treated with 2,3,5-tri-iodobenzoic acid or gibberellic acid did not produce ethylene detectable by our equipment. The hyponastic curvature induced by auxin treatment can be inhibited by exogenous application of ethylene or ethylene-generating compounds, and these treatments produce epinasty in auxin-treated leaves. Treatment with inhibitors of ethylene synthesis or action, such as aminoethoxy-vinylglycine, carbon dioxide, or heat treatment, prolong hyponasty. The planar form, therefore, appears to be affected by both hyponastic auxin effect and an epinastic ethylene effect.     

STEM ANATOMY AND INTERNODAL DEVELOPMENT IN PHASEOLUS VULGARIS

Internodal length in Phaseolus vulgaris decreases slightly from one through three, then sharply increases in four, and subsequently decreases toward the apex. Two internodes undergo rapid growth at a given time, although they do not mature concurrently. Early growth of the internode takes place throughout, with later growth limited to successively higher levels. Elongation results from both cell division and cell elongation, and the relative importance of these two phenomena is significant in determining final length. The difference in final length between internodes is brought about by rate rather than period of growth. The procambium is relatively homogeneous in structure, whereas the cambium consists of both fusiform and ray initials. During stem development the vascular meristem gradually acquires the characteristics of the cambium. By the time elongation ceases, the meristem has developed all the characteristics of the cambium.     

DEMOGRAPHIC ASPECTS OF COEXISTENCE IN ENGELMANN SPRUCE AND SUBALPINE FIR

The mechanisms for the maintenance of coexistence of Engelmann spruce and subalpine fir in subalpine forests of the Colorado Front Range were examined by comparing age, size, and spatial distributions of spruce and fir in two adjacent, previously logged sites of differing moisture availability. Adult tree ages were calculated from stem cores, while seedling ages were calculated from a multiple regression equation based on diameter, height, and number of branch whorls. Tree size was measured by height and diameter; spatial distributions were described by Morisita's index of dispersion. Cumulative age and size distributions were significantly different in the two species, with greater longevity and a larger overall size in spruce than fir. Both species showed a significant linear relationship between size and age, while fir showed a faster height growth rate than spruce. The linear relationship beween age and size was much closer in seedlings than in adults. Seedling spatial distribution was highly clumped in both species, but mature trees showed little or no clumping. Because both species are mainly wind dispersed, the greater clumping in spruce than in fir seedlings suggests that spruce have more specific establishment requirements than fir. Colonization patterns indicated that spruce seedlings were primarily found in forest gaps or associated with fir canopy trees, while fir seedlings were more commonly found in the forest, associated with either spruce or fir canopy trees. Tree density, growth rates, and mortality rates were higher in the wet site, with spruce showing the largest between site differences. These data suggest a new hypothesis for coexistence stating that Engelmann spruce and subalpine fir are maintained as codominants because the greater longevity and size of spruce is balanced by the faster height growth and more flexible seedling establishment requirements of fir.