毛状体
Stomatal apparatus 气孔器
A stomatal crypt of Nerium olender under SEM. 扫描电镜下的夹竹桃气孔穴
Lower epidermis in
Elytrostrachys (Paoceae) 禾本科
气孔频率/平方厘米
Mechanism of stomata open and close 气孔关闭的机理
穿孔
Minor veins show all mesophyll
cells are close to one vein or another. 细脉表明所有叶肉细 胞总是与某一个叶脉接近。
In a large lateral vein 大侧脉的纵切面
Structure of main vein 主脉的结构
Morphology of leaves 叶的形态
Leaves of Dicots, 双子叶植物的叶
1. Complete leaf 完全叶
Complete leaf composed of petiole, blade and stipule. 完全叶由叶柄、叶片和托叶组成。
2. Incomplete leaf 不完全叶
Dorsiventral (bifacial) leaf (异面叶) ：
Palisade Parenchyma （2 layers of Cells)
Spongy parenchyma
Mesophyll under SEM. 扫描电镜下的叶肉
Leaf structure of lilac, Syringa vulgaris 丁香叶的结构
细脉和其它的细脉联合形成一个连续的网络。细脉的网状式 样是双子叶植物的主要特征。
6. Parallel venation --- Characteristic of monocots 平行脉 --- 单子叶植物的特征 The detail from corn (Zea mays) leaf shows parallel venation of the major veins. Careful observation of such leaf lamina shows that veins do branch and converge in places, especially near the base and apex of the blade.
HydathБайду номын сангаасde 排水器
Strawberry leaves with drops of guttation water at vein endings along the edges. 草莓在叶缘具有吐水现象
Guttation is caused by root pressure
Fragaria 草莓
and over two petiolules 单叶：一个叶柄，一个叶片； 复叶：2个以上叶片（小叶片）和2个以上
小叶柄
4. Simple leaf and compound leaves 单叶与复叶
Populus sp. 杨树
Pisum 豌豆
Compound leaves
复叶
pannately compound leaves 羽状复叶
B. Mesophyll 叶肉
Dorsiventral (bifacial) leaf (两面叶) ： mesophyll can be diveded into palisade tissues and spongy tissues. 叶肉可以分为栅栏组织和海绵组织
栅栏组织
叶肉 海绵组织
Ligustrum 女贞叶片横切
Section 4
Morphology, structure and development of leaves 第四节 叶的形态、结构及生长发育
Leaves, the lateral organs of a shoot, typically have a more-or-less flattened form, and a dorsiventral （背腹 面）structure. The upper (or adaxial，近轴） and lower (abaxial，远轴) sides of the leaf with respect to the stem are easily distinguished. In most plants, leaves are dorsiventral in their internal structure.
1 = adaxial epidermis, 2 = palisade mesophyll, 3 = spongy mesophyll, 4 = intercellular space, 5 = xylem of minor vein 6 = phloem of minor vein, 7 = bundle sheath, 8 = bundle sheath extension, 9 = abaxial epidermis, 10 = stoma
Stomatal apparatus 气孔器 Stomatal apparatus are often distributed in lower epidermis. Epidermis cells is of different shape in different plants. 气孔器常分布下表皮, 在不同植物中表皮细胞有不同的形状。
The stem has 11 bundles, 3 of which produce leaf Traces that enter the petiole.
2) structure of leaf blade in dicots 双子叶植物叶片结构 Blade structure is composed of upper and lower
玉米叶的细脉与主脉的平行排列模 式。仔细的观察表明叶脉在某些地方 分支和联合，尤其在叶片的顶端和基 部。
Dichotomous venation --- Characteristic of primitive plants, e.g. Ginkgo 银杏二叉分支脉 --- 原始的特征 Ginkgo is a primitive gymnosperm that is now widely cultivated. The leaves are distinctive due to the open dichotomous branching of the veins.
Lack of any one or two parts of petiole, blade and stipule. 缺乏叶柄、叶片和托叶中的任何一部分或二部分
No stipule
No petiole and stipule
3. Leaf of Paoceae, Monocots. 单子叶禾本科植物的叶.
1.叶原基; 2-3.顶端生长成 叶轴; 4.边缘生长; 5.居间生长成成熟叶
9. Structure of mature leaves 成熟叶的结构 1）structure of petiole 叶柄的结构
The structure is similar to primary structure of stem. 叶柄的结构与茎的初生结构 相似。
Blade 叶片
Leaf ligulate 叶舌
Leaf auricle 叶耳
Leaf sheath 叶鞘
4. Simple leaf and compound leaves 单叶与复叶 Simple leaf: one blade and one petiole;
Compound leaf: over two blades (leaflet)
epidermis, mesophyll and vein.
从经过中脉的横切面中，可以见到 上下表皮，叶肉和叶脉三部分组成
A. Upper and lower epidermis 上、下表皮
The epidermis is mostly a layer of cells, which is mainly composed of epidermis cells, stomatal apparatus and trichomes. 叶表皮多为一层细胞，由表皮细胞, 气孔器和毛状体 组成。
palmately compound leaves 掌状复叶
5. Reticulate venation --- Characteristic of dicots 网状脉--- 双子叶的特征 The minor veins join with other minor veins, forming a conspicuous network. The reticulate pattern of minor veins is characteristic of most dicotyledonous plants.
Unifacial leaves, 等面叶
C. veins 叶脉
From main vein --- the secondary main vein ---- the third lateral vein --- minor vein --- vein ending to mesophyll cells 从主脉 --- 2级主脉 --- 3级侧脉 --- 细脉 --- 脉梢 --- 叶肉细胞
微弱形成层
厚角细胞
主脉是叶柄的 延伸，结构近 叶柄。从上往 下为上表皮、 机械组织、木 质部、韧皮部 、薄壁细胞、 机械组织、下 表皮
Syringa 丁香
Structure of the secondary main vein 次级主脉的结构
The structure is similar to major vein, but cells of each part decrease in correspondence and different plants have differentiation. 结构基本相似，但各部分结构相应减少，各种植物有分化。