Question

Freshly liberated seeds of Xanthium do not germinate due to

• A. Impermeable mechanically resistant seed coat
• B. Immaturity of embryo
• C. Occurrence of inhibitors
• D. Absence of growth hormones

Answer 1

The correct option is A Impermeable mechanically resistant seed coat

Freshly liberated seeds of Xanthium do not germinate due to impermeable mechanically resistant seed coat. Upon fruiting, the flowers of Xanthium ripen into two brown to black achenes and they are completely enveloped by the involucre, which becomes a bur. The bur, being buoyant, easily disperses in the water for plants growing along waterways. However, the bur, with its hooked projections, is obviously adapted to dispersal via mammals by becoming entangled in their hair. Once dispersed and deposited on the ground, the seed does not immediately germinate because of the thick seed coat. Typically, one of the seeds breaks out of the seed coat and germinates and the plants grows out of the bur.
Thus, the correct answer is option A.