Question

give reason stigma of flower secret nutritive secretion​

Answer 1

STIGMA -

• The female reproductive system in a flower is made of stigma, style, and ovary.
• Stigma is the topmost receptive structure that attracts the pollen grains.
• The germination of the pollinated pollen grains takes place at this unit of the pistil.
• The stigma is a sticky and bulb-like structure that facilitates the process of fertilization in the plants.
• After pollination, stigma releases an extracellular secretion that provides energy for the formation of the pollen tube.
• The pollen tube takes the pollen grains to the ovary for the formation of the zygote through style.
• The stigma exudate is released from the cells present on the outermost surface called papillae.
• The extracellular fluid secreted contains water, secondary metabolites, cell wall precursor, sugar, lipids, proteins, and energy-giving compounds.

Answer 2

Stigma of flower secrete nutritive secretion to aid in germinating the pollen grain.

• The stigma is a part of the female flower that is adapted especially from the pistol of the flower that is altered for the reception of pollen. The stigma may be elongated, branched and feathery, just in case of wind-pollinated flowers and also in the grasses. The stigma comprises of sticky surface and may be compact.
• Pollens are received at the stigma and it totally depends upon the stigma that how pollen grains will germinate.
• Stigma consists of specialised secretory transmitting tissue that joins the stigma and the centre of the ovary. This creates a nutrient-rich tract for the growth of pollen grains.
• The stigma exudate, which means that the outermost surface of the stigma is covered with the extracellular secretion. This nutritive secretion has been generally considered as a compound and precursor of the cell wall, secondary metabolites and reservoir of water that serve as the supply of energy for quick growth of pollen tube. 

Hence, the stigma play a major role in the germination of pollen grains by secreting nutrition secretions.