1. Introductory Plant Biology
Art/Science/Knowledge
of Plant Biology
Introductory Plant Biology
Plant Structure and Major Organs:
Stems, Leaves, Flowers, Fruits, Seeds
Text Book: Chapter 6-8, pp

2. Art/Science/Knowledge
of Plant Biology
LEAVES
Text Book: Chapter 7, pp

4. Leaves Leaves – remarkably constructed solar panels
Leaves originate from leaf primordia in the buds
Most leaves have:
a stalk , called petiole (attaches leaf to the stem)
a flattened blade (light capturing area)
Sometimes leaves may lack petioles
Leaves of deciduous trees live for one season, those of conifers may function for 2-7 years

5. Art/Science/Knowledge
of Plant Propagation
Leaves
Flattened organs attached to the stems
Appear on the stem and the nodes
Primary functions:
Photosynthesis 光合作用
Transpiration (stomata， 气孔)

6. Leaves

7. Leaves
Variety of sizes: from 1 mm wide to 6 m long (2m giant water lily)
Variety of shapes
Single arranged
Compound leaves 复叶
Attached to stems at nodes
Variety of arrangements on stem:
Alternate , Opposite, Whorled
互生 对生 轮生

8. Parts of a leaf 单叶 复叶 Source:
Bridwell, Landscape Plants: Their Identification, Culture, and Use. 单叶 复叶
Parts of a leaf

9. 中脉 叶柄 叶片 叶脉

10. Principle veins in leaves: parallel, dichotomous,
pinnate, and palmate venation

12. Internal structure of leaves
Epidermis 表皮
Mesophyll 叶肉细胞
Veins 叶脉
(vascular bundles)
维管束

13. Internal structure of leaves
Epidermis + cuticle角质 + (wax)
Mesophyll
Veins (vascular bundles)
Stomata (guard cells)
Mesophyll and veins
Bulliform cells （泡状细胞，运动细胞） – some monocots
On either side of the central vein

15. Internal structure of leaves
Vascular bundles:
Xylem and phloem tissues surrounded by a jacket of parenchyma cells called bundle sheath
维管束鞘

16. Internal structure of leaves
Veins give leaves the “skeleton”
Monocot leaves have parallel veins and do not have mesophyll differentiated into palisade and spongy layers.
Stomata (from 1000 to 1 million per square centimeter) – regulation of transpiration and turgor movements
“guttation 吐水” - non stomatal!!!

17. Stomata 气孔

18. Guttation 吐水

19. Tropical plants and Temperate plants
Specialized Leaves
Tropical plants and Temperate plants
Shade leaves (fewer mesophyll and fewer chloroplasts)
Leaves of arid regions (dry, hot regions) – thick leathery leaves with less stomata and layer of hypodermis （下皮）to avoid water loss.
Leaves of aquatic regions (wetlands) – less xylem and phloem, mesophyll not differentiated to palisade and spongy type.
Leaves of conifers 松树 (needles)
Tendrils (climbing), spines (cacti), thorns and prickles (raspberries 树莓)
Storage leaves (onion)
Reproductive leaves (kalanchoe)高凉菜 -景天科植物
Floral leaves – bracts (poinsettia)一品红 –大戟科植物

20. Specialized Leaves
Tendrils
cacti

21. Specialized Leaves
poinsettia

22. Specialized Leaves
Reproductive leaves
Kalanchoe
高凉菜 -景天科植物

23. Specialized Leaves cont’d
Insect - trapping leaves:
Pitcher plants
Sundews
Venus’s Flytraps
Bladderworts
茅膏菜
捕蝇草 狸藻

24. Pitcher plants

25. Pitcher plants

26. Specialized Leaves cont’d
Insect - trapping leaves:
Pitcher plants
Sundews
Venus’s Flytraps
Bladderworts
茅膏菜

27. Specialized Leaves cont’d
Insect - trapping leaves:
Pitcher plants
Sundews
Venus’s Flytraps
Bladderworts
捕蝇草

28. Bladderworts 狸藻

29. Bladderworts 狸藻

30. Leaves Fall changes in leaf colour Breakdown of chlorophyll
Increase in anthocyanins 花青素 and carotenoids

31. Leaves Abscision 落叶 Shading leaves – deciduous plants 落叶植物
Changes in abscission zone 离区

32. Formation of leaf abscission layer.离层

33. Art/Science/Knowledge
of Plant Propagation
Human use of Leaves
Medicine
Tinctures (药酒，酊剂), narcotics, poisons (cocaine, belladonna 颠茄)
Food and beverage
Salads, teas, alcoholic drinks
Smoking
Tobacco, marihuana (大麻)
Dyes for fabrics

34. Art/Science/Knowledge
Summary Questions
Art/Science/Knowledge
of Plant Propagation