第五章植物器官的结构及组织分化

第五章植物器官的结构及组织分化 四、花 Flower

are two species of Wolffia, up to 1 milli- meter long. (b) A flowering plant of W. borealis, with a circular concave stigma (looking like a tiny doughnut) and a min- ute anther just above it, both protruding from a central cavity. The whole plant is less than 1 millimeter long. (c) Flower- ing plant of L. gibba; two stamens and a style protrude from a pocket on the upper surface of the plant. The duckweeds (family Lemnaceae) are the smallest flowering plants; their struc- tural features mark them as extremely reduced relatives of the aroid family (Araceae), the family that includes calla lilies (Zantedeschia) and Philodendron. (a) A honeybee resting on a dense float- ing mat of three species of duckweed. The larger plants are Lemna gibba, about 2 to 3 millimeters long; the smaller ones

(b) Flowers and fruits of the banana plant (Musa X paradisiaca). The banana flower has an in- ferior ovary, and the tip of the fruit bears a large scar left by the fallen flower parts . (c) Rice (Oryza sativa) is a member of the grass family. Monocots. (a) A member of the palm family, ily, the coconut palm (Cocos nuci- fera), grozoing in Tehuantepec, Oaxaca, Mexicon. The fruit of coconut is a drupe, not a nut (see Chapter 19).

function of the leaves. (c) Round-lobed hepatica (Hepatica americana), which flowers in deciduous woodlands in the early spring. The flowers have no petals but have six to ten sepals and numerous spirally arranged stamens and carpels. (b) Saguaro cactus (Carnegiea gigantea). The cacti, of which there are about 2000 species, are almost exclusively a New World family. The thick, fleshy stems, which store water, contain chloroplasts and have taken over the photosynthetic

总状花序 圆锥花序穗状花序伞房花序伞形花序

复伞形花序 头状花序柔荑花序

肉穗花序

（一）花的组成与基本结构 花柄 Pedicel 花托 Receptacle 花被 Perianth 雄蕊群 Androecium 雌蕊群 Gynoecium 花

1、花柄和花托 周位花上位花下位花

2、花被 花萼 Calyx 花冠 Corolla 萼片：由薄壁组织、维管系统及表皮层组成 Sepal 表皮层上有气孔和表皮毛花瓣：由薄壁组织、维管系统及表皮层组成 Petal 表皮层细胞的垂周壁呈波纹状或内脊，表皮层上有气孔和表皮毛薄壁组织中可含有一些异细胞，成熟花瓣中有有色体或细胞液中有花青素

3、雄蕊群 花药Anther 花丝 Filament 4、雌蕊群基本单位是心皮 Carpel 子房Ovary 花柱 Style 柱头 Stigma

Parts of a lily (Lilium henryi) flower. (a) An intact flower. In some flowers, such as lilies, the sepals and petals are similar to one another, and the perianth parts may then be referred to as tepals. Note that the sepals are attached to the receptacle below the petals.

(b) A partly dissected flower with two tepals and two stamens removed to reveal the ovary. The gynoecium consists of the ovary, style, and stigma. The stamen consists of the filament and anther. Note that the sepals, petals, and stamens are attached to the receptacle below the ovary, which is made up, in the lily flower, of three fused carpels. Such a flower is said to be hypogynous.

The wall of the pollen grain serves to protect the male gametophyte on its often lIozardous journey between the anther and the stigma. The outer layer, or exine, is composed chiefly of a substance known ossporopollenin, which appears to be a polymer composed chiefly of carotenoids. The exine, which is remarkably tough atld resistant, is often elaborately ~culptured. The sculpturing of pollen grain walls is very precise and distinctly different from one species to another, as revealed ill these scanning electron micrographs of pollen grains. (a) Pollen grains of the horse chestnut (Aesculus hippocasta- num). The pore of each grain through which a pollen tube may emerge is vis- ible in the furrow. (b) Pollen grains of a lily (Lilium longiflorum). (c) Detail of the surface of a lily (L. longiflorum) pollen grain. (d) Pollen grain of the western ragweed (Ambrosia psilosta- chya). The pollen of ragweed is a primary cause of hay fever. Spiny pollen grains such as these are common among members of the sunflower family, Aste- raceae, of which ragweed is a member.

Mature pollen grain of Lilium, contain- ing a two-celled male gametophyte. The spindle-shaped generative cell will divide mitotically, giving rise to two sperm; the larger tube cell, which contains the generative cell, will form the pollen tube. The round structure above the generative cell is the tube cell nucleus, with its red-stained nucleolus.

Mature pollen grains--three-celled male gametophytes of the telegraph plallt, Silphium (family Asteraceae). Prior to pollination, each pollen grain contains two filamentous sperm cells, which are suspended in the cytoplasm of the larger tube cell. In other words, the pollen of Silphium is shed at the three-celled stage, whereas that of Lilium, shown in the preceding figure, is shed at the two-celled stage.

侧膜胎座 中轴胎座特立中央胎座

Lilium. Some stages in development of all ovule and embryo sac. (a) Two young ovules, each with a single, large megasporocyte. Integuments have not begun to develop. (b) Ovule now has integuments. The megasporocyte is in the first prophase of meiosis. (c) Ovule with eight-nucleate embryo sac (only six of tile nuclei can be seen here, two at the chalazal end and four at the micropylar end). The polar nuclei have not yet migrated to the center of the sac.

种皮 Seed coat 胚 embryo 胚乳 endosperm 子叶胚芽胚轴胚根五、种子 Seed 珠被受精卵受精极核

六、果实 Fruit 外果皮中果皮内果皮子房壁胚珠果皮 pericarp 种子seed 以果实成熟时果皮的性质，分为肉果和干果： 1、肉果浆果 berry 核果drupe 梨果pome 瓠果、柑果

2、干果 裂果：荚果 legume Dehiscent 蓇葖 follicle 蒴果 capsule 角果闭果：瘦果 achene indehiscent 翅果 samara 坚果 nut 颖果 caryopsis

第五章 植物器官的结构及组织分化