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Responses to Gravity and Touch 02:26

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Gravitropism: Plant Responses to Gravity

Higher plants sense gravity using statocytes, cells found near the vascular tissue in shoots, and in the root cap columella in roots. Statocytes contain starch-filled organelles called statoliths. The statoliths settle, or sediment, at the bottom of the statocyte in the direction of gravity.

Statolith sedimentation triggers a signaling cascade, resulting in the asymmetrical distribution of the plant hormone auxin across root and shoot tips. This...

Humoral Immune Responses 01:36

83.5K

Overview

The humoral immune response, also known as the antibody-mediated immune response, targets pathogens circulating in “humors,” or extracellular fluids, such as blood and lymph. Antibodies target invading pathogens for destruction via multiple defense mechanisms, including neutralization, opsonization, and activation of the complement system. Patients that are impaired in the production of antibodies suffer from severe and frequent infections by common pathogens and unusual...

Responses to Drought and Flooding 02:41

12.0K

Water plays a significant role in the life cycle of plants. However, insufficient or excess of water can be detrimental and pose a serious threat to plants.

Under normal conditions, water taken up by the plant evaporates from leaves and other parts in a process called transpiration. In times of drought stress, water that evaporates by transpiration far exceeds the water absorbed from the soil, causing plants to wilt. The general plant response to drought stress is the synthesis of hormone...

Responses to Salt Stress 02:02

14.5K

Salt stress—which can be triggered by high salt concentrations in a plant’s environment—can significantly affect plant growth and crop production by influencing photosynthesis and the absorption of water and nutrients.

Plant cell cytoplasm has a high solute concentration, which causes water to flow from the soil into the plant due to osmosis. However, excess salt in the surrounding soil increases the soil solute concentration, reducing the plant’s ability to take up...

Responses to Heat and Cold Stress 02:45

14.7K

Every organism has an optimum temperature range within which healthy growth and physiological functioning can occur. At the ends of this range, there will be a minimum and maximum temperature that interrupt biological processes.

When the environmental dynamics fall out of the optimal limit for a given species, changes in metabolism and functioning occur – and this is defined as stress. Plants respond to stress by initiating changes in gene expression - leading to adjustments in plant...

Photoreceptors and Plant Responses to Light 02:00

28.4K

Light plays a significant role in regulating the growth and development of plants. In addition to providing energy for photosynthesis, light provides other important cues to regulate a range of developmental and physiological responses in plants.

What Is a Photoreceptor?

Plants respond to light using a unique set of light-sensitive proteins called photoreceptors. Photoreceptors contain photopigments, which consist of a protein component bound to a non-protein, light-absorbing pigment called...