Seed coat effects, Biology

Assignment Help:

Seed Coat Effects

In some seeds dormancy is imposed by the presence of the seed coat; if this is removed, the seed germinates. Two possible types of mechanisms could be involved, one biochemical or physiological and the other purely mechanical.

Scarification

The seed coat is nearly impervious to the diffusion of gases. Wareing's group found that seeds of Birch (Betula Pubescens), which would not germinate intact, would do so if the seed coat were scratched or broken. Moreover, added oxygen greatly stimulated germination of such damaged seeds. Evidently the embryos themselves were not dormant; they would germinate if isolated from the seed An alternative possibility is that the seed coat might prevent the leaching out of a diffusible inhibitor. The second, or mechanical alternative has been investigated by Y. Esashi and A.C. Leopold using seeds of Xanthium pennsylvanicum (also called Xanthium strumarium), the cocklebur.

This plant produces two kinds of seeds in each fruit large, non dormant ones and small, dormant ones. The investigators used the specially designed apparatus to show that neither type of seed generates enough force to rupture the testa during imbibitions. During growth, however, the large, non dormant seeds generate sufficient force to break it whereas the smaller dormant seeds do not. This shows, for Xanthium at least, that the long held opinion that the embryo must generate sufficient force during germination to rupture the seed coat is correct. Moreover, it is clear that the forces generated by imbibitions alone are not sufficient. Active growth is also needed.


Related Discussions:- Seed coat effects

What do you understand by carcinogens, Q. What are carcinogens? The Car...

Q. What are carcinogens? The Carcinogens are factors capable of producing neoplasias and any mutagen, a substance that can induce DNA mutation, is a potential carcinogen. Insta

POPULATION, WHAT ARE THE CHARACTERISTICS OF POPULATION IN ANIMAL

WHAT ARE THE CHARACTERISTICS OF POPULATION IN ANIMAL

Observing the development of flowers into fruit, Observing the development ...

Observing the development of flowers into fruit Collect specimens of flowers in dissimilar stages of maturity from newly opened buds to specimens in which the petals have falle

What are epithelial tissues, What are epithelial tissues? What are their ge...

What are epithelial tissues? What are their general function and how is that function associated to the features of the tissue? Epithelial tissues, also known as epithelia, are

Describe microtubular cytoskeleton in protozoans, Protozoans have endoskele...

Protozoans have endoskeletons formed from microtubular cytoskeleton of the exoskeletons or cytoplasm secreted as shells or tests. Some of these single-cell organisms are capable of

Photosynthesis, why is a potted plant destarched before starting the experi...

why is a potted plant destarched before starting the experiment to investigate the factors necessary for photosynthesis

What are the major bone surfaces, Bone Surfaces:  There are four major bon...

Bone Surfaces:  There are four major bone surfaces: 1) Periosteal (outer surface of all bones) 2) Endosteal (inner surface of cortical bone) 3) Haversian (inner surface o

Explain somatic cell, For a somatic cell with 2n = 4, which of the followin...

For a somatic cell with 2n = 4, which of the following is true? (Note: G1- growth phase 1, G2 - growth phase 2, M - metaphase, P - prophase and T - telophase) a.  (Number of

Segments of environment:, Segments of Environment: The environment ...

Segments of Environment: The environment is not a simple distribution of gases but is highly complex and structured. It comprises of four segments:   Lithosphere

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd