External structure of leaves, simple and compound leaves
Lessons 15–16 · 2 lessons · O. Pratov, A. Tukhtaev, F. Azimova, I. Saparboev, M. Umaraliyeva. Biology (Botany), Grade 6. O‘zbekiston Publishing House, Tashkent, 2017
16
Simple and compound leaves
Textbook: pp. 38–39
GoalDistinguish simple and compound leaves, their kinds and blade shapes.
New words
simple leaf · oddiy bargcompound leaf · murakkab bargleaflet · bargchaodd-pinnate leaf · toq patsimon barg
Explanation
If a petiole bears a single blade, the leaf is simple (apple, pear, apricot, mulberry, grape, poplar, cotton). If one common stalk bears several leaflets on their own small stalks, the leaf is compound. Compound leaves are: trifoliate (clover, alfalfa, bean, mung bean, strawberry), palmate compound (horse chestnut), odd-pinnate — the common stalk ends in one leaflet (walnut, licorice, dog rose), even-pinnate — leaflets in pairs (peanut); in pea and vetch the end leaflets are replaced by tendrils. Simple leaves can be round, ovate, heart-shaped, lanceolate and so on, and the margin may be entire, toothed, serrate or lobed. In saksovul and qandim the leaves have become tiny scales no longer than 2 mm — this reduces water loss in dry, hot places.
Worked examples
Strawberry has a compound trifoliate leaf: three leaflets on one stalk. Walnut has an odd-pinnate compound leaf: pairs of leaflets with one at the tip.
Radish and turnip leaves are simple (deeply lobed), beet leaves are simple; carrot leaves are compound — divided into many fine parts.
Class activity
“Simple or compound?”: the teacher shows a leaf or picture and pupils raise cards “S” (simple) or “C” (compound); if compound they name the type (trifoliate, odd-pinnate…). Dry collected leaves and stick them in a herbarium notebook (do not touch thorny or unknown plants).
Practice
1
What is the main difference between a simple and a compound leaf?
A simple leaf has one blade on the petiole; a compound leaf has several leaflets.