Q.(a) How sex is determined in monoecious plants ? Write their genes involved in it. OR

(a) In monoecious plants like maize, genes such as Tassel seed (Ts) and Barren stalk (Ba1) regulate whether floral primordia develop as male or female on the same plant; (b) GM foods bring real yield/resistance/nutrition benefits but also carry real health, ecological, and socio-economic risks.

(a) Sex determination in monoecious plants

Monoecious plants bear both male and female (unisexual) flowers on the SAME individual plant (unlike dioecious plants, which have separate male and female individuals). Maize (Zea mays) is the classic textbook example: the male flowers are borne in the tassel at the very top of the plant, while the female flowers are borne in the ear(s) lower down on the stalk.

The developmental decision of whether a given floral primordium becomes male or female is genetically controlled, and specific genes have been identified in maize:

• Tassel seed (Ts) genes (e.g. Ts1, Ts2): these genes normally act to suppress female (pistil) development in the tassel, allowing it to develop purely as a male structure. When a Ts gene is mutated/non-functional, this suppression fails, and florets in the tassel instead develop female structures (seeds) -- effectively feminising what should have been a purely male inflorescence.
• Barren stalk (Ba1) gene: this gene is required for the normal initiation and development of the ear (the female inflorescence); a loss-of-function mutation in Ba1 results in a plant that fails to form ears (a barren stalk), showing that Ba1 is essential for female flower development.

Together, such genes act during development to ensure that male flower structures develop correctly in the tassel and female flower structures develop correctly in the ear on the very same monoecious plant, keeping the two sexes properly separated in space despite being on one individual.

(b) Benefits and risks of Genetically Modified (GM) foods

Benefits:

• Higher crop yields through built-in resistance to insect pests (e.g. Bt cotton/Bt brinjal) and tolerance to herbicides, reducing crop losses.
• Reduced dependence on chemical pesticides, since pest-resistance genes are built into the plant itself.
• Improved nutritional content -- for example, Golden Rice is engineered to produce beta-carotene (a vitamin-A precursor) to help address vitamin-A deficiency.
• Improved shelf life and transport/storage tolerance in some GM produce.

Risks: …