Chapter 22, Problem 5STP

Summary Introduction

Introduction:

Water, food and other substances are transported throughout the plant with the help of vascular tissues in plants. Vascular tissue is of two type phloem and xylem. Xylem helps in transportation of water and dissolved minerals from roots to other part of plants and phloem helps in transportation of food (starch) from leaves to other part of plants.

Answer to Problem 5STP

Correct answer:

The correct answer is option (d) vascular tissue.

Explanation of Solution

Explanation/justification for the correct answer:

Option (d) vascular tissue. The vascular tissue helps in transportation of food, water and other dissolved substances. Development of vascular tissues in plants contributed most to the evolution of large trees because in large trees transportation of water and minerals from roots to topmost leaves of plants is difficult due to gravitational pull. Thus, a developed vascular tissue helps in proper transportation of water, food and dissolved substance. So, the correct answer is option (d).

Explanation for incorrect answer:

Option (a) alteration of generations. Alteration of generations is also known as metagenesis. Plants alternate between the haploid gametophyte and diploid sporophyte, and between sexual and asexual reproduction. So, alteration of generation cannot be a correct answer.

Option (b) flowers. Flowers are the reproductive structure found in all flowering plants. Flowers can be unisexual or bisexual. Unisexual flowers have only the female or male reproductive organ and bisexual flowers have both male and female reproductive organs. Male reproductive organ is known as androecium and female reproductive organ is known as gynoecium. So, flowers cannot be a correct answer.

Option (c) seeds. Ovule after fertilization develops into seeds. Seeds are an embryonic plant inside a seed coat which is formed from the integuments of the ovule. Formation of seeds is an important development in reproduction which helped angiosperms and gymnosperms to survive on land. So, seeds cannot be a correct answer.

Conclusion

Development of vascular tissue in plants contributed most to the evolution of large trees. Hence, the correct answer is option (d) vascular tissue.