Effects Of Low Light Density On Photosynthetic And Physiological Characteristics Of Pepper Seedlings

In this paper,two different pepper materials were used as test materials,the low light resistant variety H09 and the low light intolerance variety J02,and the aim of the present work was to investigate differences in their physiological characteristics,fast chlorophyll fluorescence dynamics,antioxidant system,energy metabolism,and endogenous hormone under the low light conditions.Analysis of the different performance of different varieties in these changes is intended to provide a more reliable theoretical basis for the selection and evaluation of pepper-resistant low germplasm resources.The main research work and results completed are summarized as follows:1)The height of the plant height,leaf length and leaf width of the low light intolerance variety J02 and low light resistant variety H09,which are not tolerant to low light stress,increase slowly after exposure to low light stress.H09 increased leaf length and leaf width compared to J02,indicating that plants will increase leaf area in order to absorb light.2)Both J and I points of the two pepper materials increased while P point was postponed and decreased slightly,implying that photosynthesis was disturbed.Suppressed in the process of electron transfer,weak light stress weakens the assimilation force production and regulation ability of pepper photosynthetic apparatus.Fv/Fm did not change much,but PIabs changed significantly,indicating its sensitivity to low light stress.Vj of J02 increased by about 27%,Vi increased by about 23%,Sm decreased by about 21%;V09 of H09 increased by about 23%,Vi increased by 16%,and Sm decreased by about 25%.The light energy?REo/CSm?transmitted from the unit reaction center of J02 and H09 to PSI is also significantly reduced,and electron transport is suppressed.3)The hydrogen peroxide content of J02 is significantly faster than that of H09.It has its own defense mechanism against low light and avoids the accumulation of H₂O₂ to cause damage to the plants.The content of MDA in J02 increased obviously,but the difference of total antioxidant capacity in leaves of different pepper varieties was not significant.4)The decrease of ATPase activity in leaves of H09,a pepper seed resistant to light,was slow and the decrease was relatively small.The enzyme activity in the low light intolerance variety J02 leaves declined rapidly and the decline rate was relatively large.This shows that the ability of J02 to adapt to low light stress is not as good as that of H09,which may lead to an increase in mitochondrial content.Under low light stress conditions,the ATP content of H09 increases or slightly decreases,and the energy charge maintains a relatively high energy charge,which ensures the normal progress of various metabolic activities and enhances the ability to withstand low light by direct and indirect effects,and this shows adaptability to weak light stress.5)The ABA content in J02 leaves was higher than that in H09 during the whole test period from 0d to 15d.Compared with 0d,the content of CTK in leaves of J02 decreased by nearly62%at 12d,the content of CTK in leaves of H09 decreased by about 22%from 0d at 7d,and decreased by nearly 48%from 0d at 12d.There is no significant difference in JA content.