| Carex diaoluoshanica is a perennial herb of the genus Carex,as a new specieshad been found in Diaoluoshan National Nature Reserve by H.B.Yang in 2014.According to the IUCN(2001)category and criteria,C.diaoluoshanica is a endangered species.Therefore,it is a scientific problem that needs to find out the endangered mechanism.In this paper,based on the principles and methods of breeding biology,the flower characteristics,flowering phenology,floweringdynamics,breeding system,light and water effects on growth and physiology of C.diaoluoshanica were studied from the aspects of reproductive process and environmental factors.The main results are as follows:1.The floral features:In addition to the basic features that have been reported before,the description is more detailed and accurate and new features was found:Terminal spike male,lateral spikes female but with 1-2 male flowers on spikelet apex.2.The flowering phenology and flowering dynamics:The flowering period of C.diaoluoshanica was mainly from April to July.The flowering period of the population lasted for about 26 days.On the 12th day after the initial flowering stage,it entered the flowering stage.The flowering synchronization index was 0.16,and the flowering was extremely asynchronous.The terminal spikes bloom from basal to apex,and the flowering period is about 5 days.Female flowers of lateral spikes first blossom,and then male flowers blossom.3.The pollen viability and stigma receptivity:Pollen of C.diaoluoshanica has no vitality before anther dehiscence.The highest viability of loose powder is 85%,then gradually decreases.After 4h,the activity is only 27%.The stigma has been on the day before loose powder.It is admissible,the day of the loose powder and the second day can be the most instructive,the stigma can be granted for 4d.4.The breeding system:The pollen ovule ratio of C.diaoluoshanica is 1003.33±177.33.The stigma is already available before the anther cracking,the outcrossing index is 2,combined with pollen ovule ratio,outcrossing index and fruit set rate.The bag test determined that C.diaoluoshanica is a hybrid mating system with self-crossing and heterozygous fertility.5.Effects of light and water on the growth and physiology of C.diaoluoshanica:The biomass,leaf relative water content,photosynthetic parameters,and the relative water content of the leaves of C.diaoluoshanica were measured under the two-factor treatment of three water levels and four light levels.The results show that:The relative water content and photosynthetic rate of C.diaoluoshanica under 30%(W3)water condition were the lowest,malondialdehyde content and relative conductivity was the highest,and the low water condition was severely inhibited the growth of C.diaoluoshanica,but the indicators of 40%light and 30%water(L3W3)performed relatively well,indicating that proper shading can help reduce the damage caused by water deficit and promote its growth.Under full light(L1)conditions,the relative water content and photosynthetic rate were lower,and the content of malondialdehyde was higher.The photosynthetic rate of C.diaoluoshanica under high light conditions was significantly reduced and growth was inhibited.Under the condition of sufficient water,there was no significant difference between the chlorophyll content and the photosynthetic rate under 30%(L3)and 10%(L4)light treatment,indicating that C.diaoluoshanica has certain tolerance to negative.In summary,C.diaoluoshanica is sensitive to changes in light and water.40%light and 70%water are the best growth environment.The results of this experiment are similar to their original habitats.Based on the above findings,it is found that the causes of the endangerment of C.diaoluoshanica may be as follows:(1)The population is small,the number of outcrossing objects is small,and the self-crossing is dominant,which easily causes self-recession;(2)Flowers are not synchronized,resulting in a lower chance of crossing;(3)pollen viability has a short duration and is easily affected by the environment;(4)Sensitivity to light and water changes,and the growth condition is susceptible to the environment. |
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