Step 1: Understanding the Problem:
Plants like {Viola}, {Oxalis}, and {Commelina} produce two types of flowers: chasmogamous (open flowers) and cleistogamous (flowers which do not open at all).
Step 2: Approach and Formula:
Determine the reproductive consequences of cleistogamy in relation to pollination dependency and genetic variation in the offspring.
Step 3: Detailed Explanation:
Let's evaluate each given statement:
- Statement a: "They have exposed anthers and stigma." Incorrect. Since cleistogamous flowers never open, their anthers and stigmas are never exposed to the outside environment.
- Statement b: "They produce assured seed set." Correct. The anther and stigma lie close to each other internally. Upon dehiscence, pollen lands directly on the stigma, assuring seed set even in the complete absence of external pollinators.
- Statement c: "They need pollinators for pollination." Incorrect. They undergo mandatory self-pollination (autogamy) entirely internally, requiring no pollinating agents.
- Statement d: "Variations in traits are not seen in next generation." Correct. Because they only undergo autogamy, no new genetic combinations from cross-pollination occur. The progeny remain genetically uniform to the parent.
Hence, only statements (b) and (d) are correct.
Step 4: Final Answer:
Statements (b) and (d) are correct.