AngiospermsMonocots and Dicots

Monocots

• Monocots are made up of simple flowering plants like grasses, corn, palm trees, and lilies.

• Have one cotyledon for nutrient storage

Dicots

• Dicot is short for dicotyledon. "Di" means two or a double cotyledon.

• These plants have seeds that have two cotyledons, two seed leaves of food for the embryo.

• Most of the flowers you see every day are dicots.

• Some examples of dicots are roses, sunflowers, cacti, apple, and cherry plants.

New Vocabulary

• Cotyledons provide nutrients to the developing seedling and eventually becomes the first leaf of the plant.

• In the case of dicot seedlings whose cotyledons are photosynthetic, the cotyledons are functionally similar to leaves. However, true leaves and cotyledons are developmentally distinct.

• Cotyledons are formed during embryogenesis, along with the root and shoot meristems, and are therefore present in the seed prior to germination.

• True leaves, however, are formed post-embryonically (i.e. after germination) from the shoot apical meristem, which is responsible for generating subsequent aerial portions of the plant.

a - Seedcoat, b - Endosperm, c - Cotyledon, d - Embryo

Seed Components

• A seed contains all of the genetic information needed to develop into an entire plant. It contains three parts.

• (1) Embryo-a miniature plant which will grow when conditions are favorable.

• (2) Endosperm-built in food supply for the plant.• (3) Seed Coat—Hard outer covering, protects the

seed from disease and insects. Prevents water from entering the seed before the proper time.

Seeds•The radicle is the part of the embryo which emerges first.

Once outside it develops into a main root, producing root hairs and secondary roots. •-The plumule is like a leaf in its early development. •-The hypocotyl is the space between the radicle and the plumule. It develops into a stem. •The endosperm is the food supply contained in the seed. This is sometimes included in the cotyledons, which either achieve the function of primary leaves or

food storage, even both of them in some cases. •According to the number of cotyledons, we classify plants in two groups: monocotyledons or monocots and dicotyledons or dicots. In the first group we find so important plants as cereals, palms, lilies, tulips or orchids. T

he members of the second group are more numerous and comprises most of the trees and flowers. •The seed coat or testa - is the outer layer of the seed. •The micropyle is a litle pore on the seed coat , through which, apart from entering the sperm, the seed absorbs water to begin germination.

Seed Germination

• Germination-Seed embryo goes from a dormant state to an active, growing state.

• Conditions for germination— 1. The seed absorbs water through the seed coat 2. The seed has oxygen 3. The seed has a favorable temperature 4. Some species, require light (Celery) others darkness. 5. Dormancy Period

Monocot vs. dicot flowers: left is spiderwort, a monocot; right is phlox. a dicot.

Leaves of monocots generally have parallel venation whereas leaves of dicots generally have netted venation.

Monocot vs. dicot leaves: left is daylily, a monocot; right is mint, a dicot.

Monocot stem (left) and dicot stem (right).Monocot stem (left) and dicot stem (right).Monocot stem (left) and dicot stem (right).Monocot stem (left) and dicot stem (right).

Monocot stem (left) and dicot stem (right).

When pollen reaches the stigma, it grows a pollen tube to extend down the style

Form and Function

Flower Trait PollinatorReduced sepals and petals

Wind

Large sepals or petals

Animal

   Petals white Moth or bat   Petals colored        Flower tubular            Sweet odor Butterfly          No odor Hummingbird      Flower not tubular

Bee or beetle

bud - an underdeveloped and unelongated stem composed of a short axis with compressed internodes, a meristematic apex, and primordial leaves and/or flowers. terminal bud - a bud at the tip of a stem responsible for terminal growth. axillary bud or lateral bud - buds along side the axis of a stem; they were produced by the terminal bud during growth; once they grow out and form a lateral stem they become terminal buds of the lateral branch. flower bud - a bud containing a floral meristem which develops into flowers; usually larger than vegetative buds. leaf scar - a scar marking the former point of attachment of a leaf or petiole to the stem. internode - the part of the stem between nodes node - part of stem marking the point of attachment of leaves, flowers, fruits, buds and other stems. lenticel - rough areas on stems (and some fruits, ex. apple) composed of loosely packed cells extending from the cortex through the ruptured epidermis; serve as "breathing pores" for gas exchange. Only occur on young stems. growth rings - bud scale scars from the last terminal bud; they denote flushes of growth (usually per year). Can be used to age stems because usually 1 set of growth rings is produced per year on temperate trees in the

Temperate Climatic Zone.