| Autumn-germinating plants was the plants which germinated in the fall and continued growing winterafter the second year in Xinjiang, we were also known as winter annual. The seeds of autumn-germinatingplants had high yield in the next year and strong resistance to cold. In this paper, we observed the behavior,morphology, physiology, plantschlorophyll fluorescence characteristics of five autumn-germinating inresponse to low temperature, and analyzed the mechanism of cold of autumn-germinating plants. We usedthe processing tomato to study the improved feasibility of crop hardiness and yield of different processingtomatos sowed in the fall. The main results were as follow:(1)Richness of Ephemeral Plants had connected with the precipitation in spring, leaf expansion, theMay of different types of precipitation, Coverage was associated with the precipitation in spring, thefruiting stage, the May rainfall. The precipitation of May and June had impact on the coverage of thewidespread species, and the precipitation in March, April, May and July were relevant to the narrow fabricscover. So we considered comprehensively that May precipitation was the key factor to affect thedistribution of Ephemerals in Gurbantonggut Desert.(2)Biomass of Lappula semiglabra germinated in autumn was three times than that of plantsgerminated in spring, the number of leaves was twice than the plants germinated in spring, and growthperiod was10d earlier than spring sprouting.(3)Electrolytic permeability of five ephemeral plants was measured at low temperatures, using logisticcurves to calculate LT50. We found the order of hardiness in five ephemeral plants was that: Tetracmerecurvata (-26.45)> Eremopyrum orientale (-23.14)> Lappula semiglabra (-13.95)> Malcolmiascorpioides (-13.85)> Arnebia decumbens (-7.73).(4)We discovered the later time autumn-germinating plants germinated, the weaker of hardiness was.The small plants that grew about15d and which biomass were less than2g were-5℃treatment, themiddle plants that grew about44d and which biomass were between2.0-4.5g were-10℃treatment and thebig plants that grew about66d and which biomass were4.5g were-15℃treatment, they all had a large areaof brown and necrosis.(5)At low temperature stress, LT50of small plant was-5.30℃, middle plant was-7.29℃, and largeplants was-11.93℃by Fv/Fm.(6)In Physiology, the soluble sugar and proline content of different sizes plants increased withdecreasing temperature at low temperature stress, and soluble sugar and proline contents wasBig>Middle>Small in each temperature treatment, which suggested that the plants enhance their hardinessby increasing proline and soluble sugar contents. MDA contents increased at first and then decreased withthe decreasing of temperature, MDA contents of small plants first reached the highest and the contents wasthe highest, which indicated that small plants suffered the most serious.(7)In fluorescence, Fv/Fm, Fv/F0, P SⅡand qp of plants showed a significant downward trend withthe temperature decreasing, which indicated that the cold treatment resulted in partial inactivation or damage of plants PSII system and inhibited the light energy to transform into chemical energy. NPQ ofplants increased at first and then decreased with the temperature decreasing, indicating that the dissipationenergy of the leaf PSII increased in thermal and the light energy of photochemical reaction was reducedunder low temperature stress, which suggested the seedlings could protect the PSII from injury or harmreduction through increasing the heat dissipation, and the reduce of the heat dissipation in late showed thatsevere cold stress could significantly inhibit PSII.(8)Different varieties of Processing tomato had different germination rate in low temperature, and thehardiness were not the same after cold acclimation. The imbibed seeds of Ken Fan No.3had a better coldresistance at low temperature. Germination rate of imbibed seeds in different processing tomato varietiesdecreased with time prolonging at0℃. At-5℃, the seeds germination rate of Ken Fan3was relativelyhigher compared with Riegel87-5and Hongza35. In the low-temperature processing, the cold acclimationseedlings in the three varieties had smaller injury index than seedlings with no treatment and showed astronger cold tolerance. Plants germinating in early spring were cold acclimation for a long time, they weredifferences in hardiness compared with the plants germinating late, so the sowing time of the crop had animpact on hardiness. |
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