Relative Humidity Induced Plant Pollen Grain Rupture and Conceptual Model Development

Qian Zhou

Asthma is a chronic respiratory disorder affecting millions of people. The disorder causes inflated bronchi and narrowed airways. Pollen particles are the critical allergens during pollination season. Pollen grains themselves are too large to enter the lower airways, but once the grains rupture, allergenic particles are released that can be inhaled. Understanding the conditions leading to pollen rupture is important in preventing allergen exposure in asthma patients. The main goal of this research is to identify the link between meteorological conditions and allergenic particles release following pollen grain rupture. The more specific objective is to identify the key driving factors behind pollen rupture and to develop a rupture mechanism model to predict pollen rupture in the natural environment. Our main hypothesis is that pollen grains absorb water through water potential difference, causing the shell of the pollen grain to swell and rupture. We have investigated the relationship between pollen grain rupture and relative humidity (RH). Parameters from these experiments have been used to develop a model describing the pollen rupture mechanism. v A small humidity exposure apparatus has been built to quantify the dependence of pollen grain rupture on RH over time. Wheat pollen grains were used in the research. The results indicate that exposure to higher RH speeds pollen grain rupture and leads to a higher rupture fraction. To better understand the thermodynamics and kinetics of water flux and the change in water potential during pollen rupture, a rupture model is being developed using parameters from the experimental work. Because changes in the surrounding water potential modify turgor pressure inside the pollen grain, this rupture model will be used to describe the whole rupture mechanism. Rupture occurs as soon as turgor pressure exceeds the strength of the pollen grain shell. From the experimental results we speculate that the pollen rupture pattern is determined by the pollen's threshold water potential, the shell's water permeability, the strength of the pollen shell, the pollen grain radius, environmental RH, and exposure time.

Relative Humidity Induced Plant Pollen Grain Rupture and Conceptual Model Development

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