第五章 植物器官的结构及组织分化

四、花 Flower

The duckweeds (family Lemnaceae) arethe smallest flowering plants; their struc-tural features mark them as extremelyreduced relatives of the aroid family(Araceae), the family that includes callalilies (Zantedeschia) and Philodendron.(a) A honeybee resting on a dense float-ing mat of three species of duckweed. Thelarger plants are Lemna gibba, about 2to 3 millimeters long; the smaller ones

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 protrudingfrom a central cavity. The whole plantis less than 1 millimeter long. (c) Flower-ing plant of L. gibba; two stamens anda style protrude from a pocket on theupper surface of the plant.

Monocots. (a) A member of the palmfamily, 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).

(b) Flowersand fruits of the banana plant (Musa Xparadisiaca). 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 ofthe grass family.

function of the leaves. (c) Round-lobedhepatica (Hepatica americana), whichflowers in deciduous woodlands in theearly spring. The flowers have no petalsbut have six to ten sepals and numerousspirally arranged stamens and carpels.

(b) Saguaro cactus (Carnegiea gigantea).The cacti, of which there are about 2000species, are almost exclusively a NewWorld family. The thick, fleshy stems,which store water, contain chloroplastsand have taken over the photosynthetic

穗状花序

伞形花序伞房花序

总状花序圆锥花序

柔荑花序

复伞形花序

头状花序

肉穗花序

（一）花的组成与基本结构

花

花柄 Pedicel花托 Receptacle花被 Perianth雄蕊群 Androecium雌蕊群 Gynoecium

1 、花柄和花托

下位花 周位花 上位花

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

子房 Ovary

花柱 Style柱头 Stigma

基本单位是心皮 Carpel

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

(b) A partlydissected flower with two tepals and twostamens removed to reveal the ovary.The gynoecium consists of the ovary,style, and stigma. The stamen consists ofthe filament and anther. Note that thesepals, petals, and stamens are attachedto the receptacle below the ovary, whichis made up, in the lily flower, of threefused carpels. Such a flower is said tobe hypogynous.

The wall of the pollen grain serves toprotect the male gametophyte on its oftenlIozardous journey between the antherand the stigma. The outer layer, or exine,is composed chiefly of a substance knownossporopollenin, which appears to be apolymer composed chiefly of carotenoids.The exine, which is remarkably toughatld resistant, is often elaborately~culptured. The sculpturing of pollen grain wallsis very precise and distinctly differentfrom one species to another, as revealedill these scanning electron micrographs

of pollen grains. (a) Pollen grains of thehorse chestnut (Aesculus hippocasta-num). The pore of each grain throughwhich a pollen tube may emerge is vis-ible in the furrow. (b) Pollen grains ofa lily (Lilium longiflorum). (c) Detailof the surface of a lily (L. longiflorum)pollen grain. (d) Pollen grain of thewestern ragweed (Ambrosia psilosta-chya). The pollen of ragweed is aprimary cause of hay fever. Spiny pollengrains such as these are common amongmembers of the sunflower family, Aste-raceae, of which ragweed is a member.

Mature pollen grain of Lilium, contain-ing a two-celled male gametophyte. Thespindle-shaped generative cell will dividemitotically, giving rise to two sperm; thelarger tube cell, which contains the gen-erative cell, will form the pollen tube.The round structure above the generativecell is the tube cell nucleus, with itsred-stained nucleolus.

Mature pollen grains--three-celledmale gametophytes of the telegraph plallt,Silphium (family Asteraceae). Prior topollination, each pollen grain containstwo filamentous sperm cells, which aresuspended in the cytoplasm of the largertube cell. In other words, the pollen ofSilphium is shed at the three-celledstage, whereas that of Lilium, shownin the preceding figure, is shed at thetwo-celled stage.

侧膜胎座

中轴胎座

特立中央胎座

Lilium. Some stages in development ofall ovule and embryo sac. (a) Two youngovules, each with a single, large mega-sporocyte. Integuments have not begunto develop. (b) Ovule now has integu-ments. The megasporocyte is in the firstprophase of meiosis. (c) Ovule witheight-nucleate embryo sac (only six oftile nuclei can be seen here, two at thechalazal end and four at the micropylarend). The polar nuclei have not yetmigrated to the center of the sac.

五、种子 Seed

种皮Seed coat

胚embryo

胚乳endosperm

子叶胚芽胚轴胚根

珠被

受精卵

受精极核

六、果实 Fruit

果皮 pericarp种子 seed

子房壁

胚珠

外果皮中果皮内果皮

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 legumeDehiscent 蓇葖 follicle 蒴果 capsule 角果

闭果： 瘦果 acheneindehiscent 翅果 samara 坚果 nut 颖果 caryopsis