Characteristic Analysis Of Chlorophyll Content And Chlorophyll Fluorescence Parameters Of C3 And C4 Plants In The Desert Steppe Of Inner Mongolia

Climate influences and human factors have led to intensified desertification of the grasslands in Inner Mongolia,resulting in serious vegetation degradation.Photosynthesis usually refers to the process by which green plants absorb light energy,synthesize carbon dioxide and water into energy-rich organic matter and release oxygen.It is the most basic way for the biological world to obtain food,energy and oxygen.According to the differences in the ways of CO₂ fixation during photosynthesis,plants can be divided into two types:C3 and C4.Chlorophyll content is the basic physiological characteristic of plants,and its content directly affects the photosynthesis capacity and photosynthetic production capacity of plants.Hyperspectral data contains continuous spectral information of ground objects,and contains rich biophysical and biochemical characteristics.Chlorophyll Fluorescence（Chlorophyll Fluorescence,Ch F）is a product of plant photosynthesis,which can directly reflect the physiological state of C3 plants and C4 plants,and is not interfered by the reflected light of other environments.This study takes C3 and C4 plants in the desert steppe of Inner Mongolia as the research object,and proposes a chlorophyll content inversion method based on hyperspectral data;using hyperspectral data,chlorophyll content data,and chlorophyll fluorescence parameter characteristic data to analyze the photosynthesis of C3 and C4 plants Characteristics;and evaluate the impact of environmental factors on the photosynthesis of C3 and C4 plants to provide a theoretical basis for regional ecological protection and the management of the desert grassland ecosystem in Inner Mongolia.The main research contents and conclusions are as follows:（1）Use Field Spec?Hand Held?2（HH2）ground spectrometer and CCM-300 chlorophyll content meter in the field using C3 plants Stipa,Allium spp.and Artemisia frigida,and C4 plants of the common forage grasses in the desert grassland of Inner Mongolia in the test site.Monitor the hyperspectral reflectance and chlorophyll content of forages,screen out sensitive bands,and establish an estimation model for forage chlorophyll content.The coefficient of determination of the inversion model from large to small is Stipa R²=0.71>Artemisia frigida R²=0.55>Salmum spp R²=0.33>Small Chenopodium R²=0.29.The determination coefficients of the C3 plant inversion model are all greater than that of the C4 plant.（2）The original spectra of the four plants show unique plant spectral reflectance characteristics.The overall spectral reflectance of C4 plants is higher than that of C3 plants,which is different from the cell structure of C3and C4 plants,and may be related to the rosette structure of C4 plants.（3）The chlorophyll content of C3 plants is wide and slightly higher than that of C4 plants.The occurrence of rainfall greatly increases the chlorophyll content of C3 and C4 plants to varying degrees.Among them,the chlorophyll content of C3 plants changes more than C4 plants,That is,the effect of increasing the water content of C3 plants in promoting the increase of chlorophyll content is higher than that of C4 plants.（4）Use 8 probes in OS5P+chlorophyll fluorometer and PSP32chlorophyll fluorometer to monitor C3 and C4 plant chlorophyll fluorescence parameters（Y（Ⅱ）,ETR,NPQ,Fv/Fm,etc.）,and obtain chlorophyll through continuous observation Daily change trend of fluorescence parameters.In general,the Y（Ⅱ）,ETR,Fv/Fm and NPQ values of C4 plants are higher than C3 plants,while Y（NPQ）and Y（NO）values are lower than C3 plants,indicating that C4 plant leaves absorb and transmit light energy.The light energy utilization efficiency and conversion efficiency are relatively high.When the light is excessive,the light energy can be converted into heat and energy consumption in a timely manner,and the ability to resist light damage is stronger than that of C3 plants.That is,C4 plants in the desert steppe of Inner Mongolia are more suitable for survival under stress conditions than C3 plants.