Page 129 - Science Course 1 (Book 1)

Plants: Responses to Stimuli Mo4-L4a: How Do Plants Respond to
Environmental Stimuli?

Lesson 4

24
In this topic, you will learn the following
lessons: 18 6
Mo.4 - L4a: How Do Plants Respond to 24
Environmental Stimuli? Long day plant Day length more than 12 hrs for flowering
Mo.4 - L4b: How Do Plants Respond to Chemical
Stimuli? 12
8
6
Mo4-L4a How Do Plants Respond to
Environmental Stimuli?
12
KEY CONCEPTS: Natural day plant Day length immaterial than 12 hrs for
1. What types of environment stimuli do plants flowering
respond to?
Let’s Begin

Vocabulary A-Z Stimuli and Plant Responses

Let us learn some vocabulary
Stimuli are any changes in an organism’s
environment that cause a response.
Stimulus A plant responds to light by growing toward it.
a change in an organism’s
environment that causes 2 Types of Stimuli
a response.

Internal Stimuli External Stimuli
Changes Inside Changes Outside

Light Light

Tropism
plant growth
toward or away
from an external
stimulus.

Photoperiodism

a plant’s response to the number of hours of dark- Environmental Stimuli
ness in its environment.
A tropism is a response that results in plant growth
The day-length requirements for flowering in three toward or away from a stimulus.
categories plant
24
When the growth is toward a stimulus, the tropism is
called positive.
18 min 6

Short day plant Day length less than 12 hrs for flowering
122