Class 11 Biology - MAHARASHTRA
Plant Growth and Development
The chapter 'Plant Growth and Development' in Class 11 Maharashtra State Board (MSBSHSE) explores the irreversible increase in size, shape, and mass of plants. It covers the phases of plant growth, mathematical representation of growth rates, and the critical role of plant growth regulators (PGRs) like auxins, gibberellins, cytokinins, ethylene, and abscisic acid. Additionally, the chapter discusses photoperiodism, vernalization, and seed dormancy. For board exams, understanding the physiological roles of different hormones and distinguishing between arithmetic and geometric growth are crucial, as questions frequently test direct applications and biological definitions.
Start Learning FreeKey Concepts
Plant Growth
An irreversible, permanent increase in size, volume, or mass of a plant, accompanied by metabolic processes requiring energy.
Arithmetic Growth
Growth where only one daughter cell continues to divide while the other differentiates, resulting in a linear curve represented by the formula Lt = L0 + rt.
Geometric Growth
Growth where both daughter cells retain the ability to divide, resulting in an exponential curve where population size doubles over time.
Plant Growth Regulators (PGRs)
Small, simple organic molecules of diverse chemical composition that act as chemical messengers, controlling plant development and responses.
Photoperiodism
The physiological response of plants to the relative lengths of light and dark periods (day length) that triggers flowering.
Vernalization
The dependence of flowering on low-temperature treatment, ensuring that plants do not reproduce prematurely during harsh winters.
Important Formulas
Board Exam Info
In the Maharashtra (MSBSHSE) Biology board exams, this chapter typically carries about 3 to 4 marks without options, and up to 6 marks with options. Common question types include distinguishing between arithmetic and geometric growth, stating the physiological roles of specific plant growth regulators, defining photoperiodism and vernalization, and short answer questions on seed dormancy.
Frequently Asked Questions
Short Day Plants (SDP) require a light period below a critical day length to flower, whereas Long Day Plants (LDP) require light periods above a critical threshold.
Short Day Plants require a light duration shorter than a critical photoperiod to flower, while Long Day Plants require light duration longer than a critical photoperiod.
Which plant hormone is known as the stress hormone?
Abscisic acid (ABA) is known as the stress hormone because it increases tolerance to various kinds of stress, particularly water stress.
Why is geometric growth represented by an exponential curve?
In geometric growth, both daughter cells continue to divide after each cell division, leading to a rapid, exponential increase in cell number over time.
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