Stomata

Design and InstallationGarden Caregarden TriviaIndoor plantsPlant Health CareUncategorized
Written By Peter Morris

Introduction

In botany, a stoma (plural – stomata) are microscopic pores primarily found on the underside of plant leaves. The word stoma comes from Greek στόμα – mouth.

Mostly found in the epidermis of leaves, stems, and other organs – it controls the rate of gas exchange between the internal air spaces of the leaf and the atmosphere.

Structure

The pore itself is bordered by a pair of specialized cells known as guard cells that regulate the size of the stomatal opening. They have a crescent shape - which is the key to opening and closing the pore.

Function

They are the primary gateway for gas exchange in plants as well as the regulation of water vapor - transpiration. They mainly take in carbon dioxide for photosynthesis and release the oxygen produced by the plant.

By opening, stomata allow carbon dioxide to diffuse into the leaf. The plant uses this gas, along with sunlight and water, to create glucose, while releasing oxygen as a byproduct.

When open, water vapor exits the plant into the atmosphere through open stomata. This process creates a negative pressure gradient, effectively pulling water and essential nutrients up from the roots to the leaves.

The Trade-off between Gas Exchange and Water Loss is a constant balancing act.  Plant species have evolved many methods to adapt to their climates to manage this balance.

Opening and Closing

Pores open and close in response to environmental conditions and the plant's internal water pressure - turgor pressure. 

When water enters the guard cells, they swell and become turgid. Because the inner cell walls are thicker than the outer ones, the swelling causes them to curve outward – this kidney bean shape widens the pore. This typically happens during the day to allow carbon dioxide intake for photosynthesis.

When the plant is losing too much water (such as during hot or dry conditions), the guard cells lose water and become flaccid.  The cells become almost parallel, causing the pore to close and conserve moisture.

Evolutionary adaptations

Most angiosperm trees have stomata only on their lower leaf surface, but not all !

When leaves develop stomata on both leaf surfaces, the stomata on the lower surface tend to be larger and more numerous.  But some plants evolved fewer stomata but larger in size. Others evolved small stomata that were more numerous.

Classification of stomata types is based on the size, shape and arrangement of the subsidiary cells that surround the two guard cells.

Stomatal crypts are sunken areas of the leaf epidermis which form a chamber-like structure that contains one or more stomata and sometimes trichomes or accumulations of wax. These are an adaption to drought and/or windy dry climate conditions.

And now you know !

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Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBA

All photographs used with permission @SHUTTERSTOCK

Peter Morris

Peter was born and raised on a beautiful green island in the midst of a tropical rainforest. He was introduced into the world of plants at the age of six when his grandmother, an avid Spanish gardener herself, asked him to help her grow seeds for her pepper garden. He was hooked! By the time he was a teen, he had his own rose and orchid collection numbering in the hundreds. Botany was in his blood, and that is what he set out to study.

His passion brought him to NY in the late seventies to further his education. His tenacity allowed him to work full time at Plant Specialists while he completed a MS in Plant Biology. As a manager at the time he felt unsatisfied with his knowledge of business and business processes. Peter felt compelled to learn, so he then pursued and completed an MBA in Quality Management within a few short years.

Peter’s other passion is teaching. His natural ability is quickly consumed by our staff in all subjects in Botany, Horticulture, and Landscaping. He created an immense reference library of more than 3,500 plants providing an invaluable resource for our staff.

Peter’s breadth of knowledge and wisdom allows him to effectively diagnose the needs of plants. Sometimes just by walking into a garden he can create a prescription that fixes even the hardest issue. He is our Staff Botanist, Diagnostician, and all around Mentor. Recently, he has put his immense knowledge and skills into developing a new department that focuses on Plant Healthcare. As he puts it, “Magic through Science”. The PHC staff that surround him have avidly consumed his teachings. Substantially developing their own plant wisdom, many have taken on difficult plant health issues with spectacular results.

Plant Healthcare has been an instant success with customers! The proper treatment of insects and diseases including Organic methods has made pest control a necessity for every plant. Correcting hormonal imbalances caused by planting in containers or refurbishing soils leached of nutrients by irrigation systems are big challenges PHC has become quite comfortable addressing. The scientific approach to the complex demands of keeping plants healthy in our harsh city environment has made many a customer say WOW!

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