Q30.1-1CC - Campbell Biology

Question

Contrast how sperm reach the eggs of seedless plants with how sperm reach the eggs of seed plants.

Step-by-Step Solution

Answer

The male gamete in seedless is flagellated and travels to the female gamete by swimming to fertilize. The sperm travels a few centimetres to approach the female gamete.

In seed plants, the pollen grain develops a tube-like structure called a pollen tube that penetrates the egg for fertilization. The grain contains the male gamete and reaches the stigma, and pierces the ovary.

Step 1: Seed and seedless plants

The plants are multicellular eukaryotes. Those which have seeds for propagation are called seed plants. In contrast, the plants which do not have seeds for multiplication are called seedless plants. Fertilization is the fusion of male and female gametes.

Step 2: Male and female gamete fusion in seedless plants

In seedless plants, the male gamete forms a gametangium called antheridia and a female gamete called archegonium. The antheridia swim through water film and reach the archegonium.

The fusion of male and female gamete takes place inside the archegonium to form the zygote. The zygote develops into a sporophyte that produces spores by meiosis. 

Step 3: Male and female gamete fusion in seed plants

While in seed plants, the pollen grain contains male gamete in a cover called sporopollenin that protects the grain from drying. It starts developing a tube-like structure called pollen tube to rupture the ovary into the stigma of the flower inside which the process of fertilization occurs.