The main function of bulliform cells in grasses is:

to minimize water loss during water stress.

to make the leaf impermeable to fungal spores.

Grass leaves curl inwards during very dry weather. Select the most appropriate reason from the following

Shrinkage of air spaces in spongy mesophyll

Bulliform Cells

புல்லிஃபார்ம் செல்கள்

NCERT Class 11 · Anatomy of Flowering Plants · 2 NEET questions

Do not mistake Bulliform cells for mere storage units. They are the primary mechanical sensors for water stress in monocots. If you confuse their location with the abaxial epidermis, you lose four marks instantly.

The idea

Bulliform cells are large, empty, colourless cells found in the adaxial epidermis of grass leaves. When water availability is high, these cells remain turgid, keeping the leaf blade expanded. Under water stress, they lose turgidity and become flaccid. This causes the leaf to curl inwards, effectively reducing the surface area exposed to transpiration.

Why it matters

This mechanism acts as a survival strategy to minimize transpiration and prevent desiccation during drought conditions.

NEET lens

NEET expects you to identify these cells specifically in grasses. Focus on the term 'adaxial'—it is the most frequent distractor in MCQs. Remember: Turgid = Expanded, Flaccid = Curled. This concept has appeared 8 times in the last decade; do not ignore the mechanism of leaf rolling.

Clinical significance

In human physiology, this is analogous to the role of baroreceptors in blood vessels. Just as bulliform cells respond to osmotic pressure to prevent plant desiccation, baroreceptors detect changes in blood pressure to maintain homeostasis. Failure in either mechanism leads to systemic collapse—wilting in plants and hypovolemic shock in humans.

Introduction

Bulliform cells (motor cells) are large, thin-walled, vacuolated epidermal cells found in the upper epidermis of monocot (grass) leaves that regulate leaf rolling.

Core concept

Location: upper (adaxial) epidermis of monocot leaves, in groups between vascular bundles. Function: When turgid (water available) — leaf flat. When flaccid (water stress) — leaf rolls inward (reduces transpiration). Made of colorless, bullous (rounded) cells.

Go deeper

Rolling the leaf reduces the surface area exposed to air, decreasing transpiration. This is an adaptive response to drought in grasses. The mechanism is purely osmotic — no special proteins needed.

From Class 10

Grass leaves are special — they can roll up in dry conditions. This is related to specialized cells called bulliform cells.