【作者】 郝敬虹；

【导师】 李天来；

【作者基本信息】 沈阳农业大学 ， 设施园艺学， 2009， 博士

【摘要】 薄皮甜瓜（Cucumis melo L．）已成为我国北方设施园艺产业中的重要种植种类之一。然而，秋冬茬薄皮甜瓜生产中通常在果实膨大期遇到低温胁迫，严重影响植株生长和果实发育，从而导致秋冬茬薄皮甜瓜的产量和品质下降，制约了这一茬次甜瓜生产的发展。因此，弄清影响薄皮甜瓜果实膨大和糖积累的相关因素，进而制定调控不适宜温度胁迫下的栽培措施，对于提高秋冬茬薄皮甜瓜的产量和品质具有重要意义。本研究以薄皮甜瓜“玉美人"为试材，利用人工气候室，模拟我国北方秋冬季日光温室甜瓜生产的自然夜间低温，研究了夜间低温对薄皮甜瓜生育（主要指果实膨大）、果实糖积累以及内在因素的影响，明确了果实膨大期夜间低温条件下薄皮甜瓜叶片光合物质生产、光合运转糖-水苏糖代谢及其关键酶—肌醇半乳糖苷合成酶基因的表达、韧皮部超微结构、果实库强等的变化与果实膨大和糖积累的关系，揭示了夜间低温对薄皮甜瓜果实膨大和糖积累影响的相关因素，并为薄皮甜瓜糖代谢的调控提供了理论基础。主要研究结果如下：1．明确了夜间9℃低温明显抑制薄皮甜瓜的生育。其中夜间9℃低温明显抑制植株株高和茎粗的生长，分别降低4．89％和2．87％；同时明显影响根、茎、叶和果实等各器官干物质的积累；并导致干物质从果实向茎、叶等营养器官中转移，明显抑制单果质量和果实横、纵径的增加，最终使单果质量和果实横、纵径分别下降23．85％，12．14％和10．58％。夜间12℃处理对薄皮甜瓜的生育无明显影响。2．明确了夜间9℃低温明显降低薄皮甜瓜果实中糖的积累。从不同夜间低温处理对薄皮甜瓜果实中各种糖含量的影响来看，夜间9℃处理3 d后就显著降低了果糖和葡萄糖含量，而水苏糖含量的显著降低推迟到处理6 d后，蔗糖和棉籽糖含量则处理9 d后显著降低，肌醇半乳糖苷则无显著差异。处理3 d后，果实中总糖含量就极显著低于对照，且处理时间越长差异越大；夜间9℃处理3～12 d，果实中淀粉含量明显高于对照，而后期无明显变化。夜间12℃处理后果实中淀粉含量明显高于对照，且后期差异极显著，而其他糖均无显著变化。3．明确了夜间9℃低温降低薄皮甜瓜叶片中光合物质的生产。其中，夜间9℃处理大幅度降低了净光合速率、气孔导度（Gs）和蒸腾速率（Tr），差异极显著，而胞间CO₂浓度（Ci）则在处理前期明显低于对照，后期几乎无变化；气孔限制值（Ls）仅在低温处理后的6～12d显著高于对照；说明此时期气孔限制可能是导致叶片净光合速率下降的首要原因，而其他时期可能主要是非气孔因素的影响；叶绿素的变化可能与叶片净光合速率的变化具有一定的关系。而夜间12℃处理后，叶片净光合速率仅在处理后12 d明显低于对照；处理后6～9d，气孔限制值（Ls）高于对照，而光合作用的其他相关因素几乎未受影响。4．明确了夜间9℃低温限制薄皮甜瓜叶片中水苏糖代谢。首先表现在薄皮甜瓜叶片中糖和淀粉的大量积累。在处理6 d后棉籽糖含量极显著高于对照，约是对照的2倍，处理9 d后葡萄糖和果糖含量也极显著高于对照，且蔗糖、水苏糖在处理后期也显著高于对照，但变化都不如棉籽糖明显；在整个处理过程中，淀粉含量平均增加幅度为20．28％。其次，明显影响薄皮甜瓜叶片中水苏糖代谢相关酶活性。提高了AI和NI活性，并且AI活性升高倍数大于NI活性升高倍数；处理前期SS、SPS和水苏糖合成酶活性活性与对照相差不大，处理6 d后大幅度下降，差异显著；明显降低了肌醇半乳糖苷合成酶活性，且随着低温处理时间的延长，这种下降的趋势表现越强烈。最后，处理后期明显抑制了叶片中CmGAS1和CmGAS2的基因表达。而夜间12℃处理对叶片中水苏糖代谢影响不大。5．通过扫描电子显微镜观察，明确了薄皮甜瓜的子蔓包括内、外两圈维管束，内圈维管束较大，为初生维管束，外圈维管束较小，为后生维管束，且维管束中木质部的内外都具有韧皮部而形成双韧维管束。并且发现，夜间低温处理推迟了薄皮甜瓜子蔓维管束的生育期。与对照相比，夜间9℃处理12 d减慢了子蔓维管束的发育进程。具体表现为对照植株子蔓维管束内、外圈5束维管束逐渐增大，而夜间9℃处理12 d后子蔓维管束的增大幅度小于对照。但是，夜间12℃处理后未看出子蔓维管束发育状态的改变。夜间9℃低温条件下子蔓维管束缓慢的发育进程可能不利于糖的运输。6．通过透射电子显微镜观察了不同夜间温度条件下薄皮甜瓜子蔓维管束内韧皮部细胞的形态学变化，并阐明了夜间低温处理（9℃和12℃）不同程度的改变了薄皮甜瓜子蔓维管束内韧皮部细胞的超微结构。包括一般伴胞和中间细胞出现质膜内陷现象，伴胞中的线粒体数量减少，叶绿体的基粒片层也不清晰，排列不整齐，存在许多小液泡，韧皮薄壁细胞中出现较多的淀粉粒，筛管珠光壁的特征更加明显等。这些变化是细胞对低温胁迫的适应性反应，但不利于韧皮部运输。7．明确了夜间9℃处理导致子蔓和果柄维管束中糖积累。子蔓维管束中果糖和棉籽糖在低温处理3 d后就明显高于对照，葡萄糖、蔗糖和水苏糖含量则在处理9 d后显著高于对照。果柄维管束中除棉籽糖含量显著低于对照外其它糖含量都明显高于对照，差异极显著。同时，夜间9℃处理后，与子蔓维管束积累的糖相比，果柄维管束积累的运转糖总量是增加的，且主要积累蔗糖，表明夜间9℃抑制果柄维管束糖运输的程度可能比抑制子蔓维管束糖运输的程度大，这就进一步证实，在糖运输方面果柄维管束可能较子蔓维管束对低温敏感。而夜间12℃处理6 d后，子蔓维管束中肌醇半乳糖苷含量则极显著低于对照，而其他糖含量变化不明显；仅在处理末期果柄维管束中葡萄糖、果糖和棉籽糖显著高于对照，其他糖含量变化不明显。8．明确了不同的夜间低温影响薄皮甜瓜果实的库强，尤其是夜间9℃处理，主要表现在对果实中糖代谢相关酶活性、内源激素和多胺含量的影响。其中夜间9℃低温明显影响糖代谢相关酶活性。表现为大幅度提高了AI、NI和碱性α-半乳糖苷酶活性，明显降低了SS、SPS活性，差异显著。而夜间12℃处理后9 d明显提高了碱性α-半乳糖苷酶活性，对其他酶活性几乎无影响。9．明确了夜间低温明显影响薄皮甜瓜果实中内源激素含量。夜间9℃会限制赤霉素和玉米素的积累，增加脱落酸含量；且明显减小果实中GA3／ABA和ZT／ABA。夜间12℃会诱导果实膨大后期的赤霉素和生长素含量增加，处理前期GA3／ABA无明显变化，ZT／ABA明显减小。无论处理还是对照，薄皮甜瓜果实中GA3／ABA与单果质量增长率均达到极显著的相关性，且随着夜间温度的降低，其线性关系的斜率降低；除对照ZT／ABA与单果质量增长率达到极显著的相关性外，低温处理后ZT／ABA与单果质量增长率未达到显著相关。10．明确了夜间低温明显影响薄皮甜瓜果实中内源多胺含量。夜间9℃处理前期，明显降低了果实中内源腐胺、亚精胺和总多胺含量，且在整个处理时期，内源精胺含量都下降。同时，在夜间12℃处理的前期，果实中内源腐胺含量显著低于对照，其他时期变化不明显，而内源亚精胺和总多胺含量几乎无变化。从多胺与单果质量增长率的相关性分析来看，果实中腐胺、亚精胺、总多胺含量与薄皮甜瓜果实膨大具有一定的关系。更多还原

【Abstract】 Melon is a important kind in horticulture production in north area.However,lowtemperature stress usually occur during fruit enlarging in autumn in north area,which affectsthe development and reduces the quality.As a result,melon production in autumn is limitedseriously.Thus it is very important to study the related factors which cause small fruit and lowsugar of melon fruit and estabolish the planting measure to regulate the yield and qualityunder low temperature stress.Therefore,this paper studied the effects of different night low temperature on melongrowth,espaciallly fruit enlarging,sugar accumulation in fruit and their factors with thematerial of“yumeiren”.Furthermore,this paper demonstrated the relationship betweenphotosynthesis,stachyose metabolism in leaves,the transcript of galactinol synthase gene,ultrastructure changes of phloem,the factors of sink strength and fruit enlarging and sugaraccumulation in fruit during fruit enlarging under normal and night low temperaturecircumstance simulated by climate room.Finally,we demonstrated the factors which restrictfruit enlarging and sugar accumulation.In a word,this research will be helpful for controllingcarbohydrate metabolism of melon under low temperature stress.The key objectives werelisted as follows:1.It was clear that 9℃in night distinctly restricted the growth of melon.In detail,9℃in night reduced the height and stem diameter with 4.89% and 2.87% respectively.It wasdisadvantage for photosynthetic dry matter accumulation of melon plants under 9℃in night,and the distribution of dry matter in fruit decreased while other organs increased.Moreover,the single fruit weight,transverse length and vertical length were reduced at 23.85%,12.14%and 10.58% respectively after the treatment of 9℃in night.However,the effect of 12℃innight on melon development was little.2.Carbohydrate contents in melon fruit were affected by the treatment of 9℃in night.Fructose and glucose decreased after treatment of 9℃in night for 3 d while significantlydecreased sucrose content occurred in middle and later period,yet galactinol content had nochange.Meanwhile,total carbohydrate content was lower than control with markedlysignificant difference after treatment of 9℃in night for 3 d,and the difference was moreobvious as the time prolonging.Otherwise,compared with control,starch content increasedobviously at 3～12 d after treatment of 9℃in night,however,after treatment of 12℃innight,starch content increased in evidence while each carbohydrate content was almostinvariable.3.The experiment demonstrated that photosynthesis of melon fell under the treatment of9℃in night.Plants at 9℃exhibited a consistently lower net photosynthetic rate（Pn）,stomatal conductance（Gs）and transpiration rate（Tr）relative to control plants for allexperimental times,yet concentration of CO₂（Ci）only decreased at beginning of 9℃in nighttreatment.Compared with control,Ls increased after treatment of 9℃in night for 6～12 d,with significant difference,suggesting that Ls may be the important reason for the decrease of photosynthetic rate.What was more,the change of chlorophyll content may be related withthe decrease of photosynthetic rate.However,after the treatment of 12℃in night,netphotosynthetic rate was only notably affected at 12 d,Ls was bigger than control after thetreatment for 6～9 d,while the other factors related to photosynthesis were not affected.4.Stachyose metaolism in melon leaves was limited after the treatment of 9℃in night.Frist of all,the contents of carbohydrate and starch accumulated largely.A classic linearincrease in RFO concentration,particularly raffinose,was observed after 6 d of treatment at 9℃with markedly significant difference,and exhibited a nearly two times relative to control.In addition,high glucose and fructose accumulation was also observed in leaves subjected to9℃in night,and stachyose content increased obviously compared with control at the end oftreatment,but these changes were smaller than raffinose.Meanwhile,the increase of starchwith 20.28% on average in overall treatment time.Secondly,stachyose-metabolizing enzymesactivities were affected when melon plant obejected to 9℃innight.The treatment of 9℃innight led to a marked decrease in overall SS,SPS after 6 d,and a sharp increase in AI and NI,especially AI.Galactinol synthase and stachyose synthase activity also reduced in evidence,and the change was more stronger as the time prolonging.Finally,a obvious reduction ofCmGAS1 and CmGAS2 transcript was obversed at the end of treatment of 9℃in night.There was no change of stachyose metabolism in melon leaves after treatment of 12℃innight.5.The morphological observation using SEM showed that there were two circles ofvascular bundle on transverse section of side branches,and the vascular bundle in inner circlenamed initial vascular bundle was bigger while the vascular bundle in outer circle namedsubsequent vascular bundle was smaller,and each vascular bundle had two phelom.Thetreatment of 9℃in night postponed the development period of vascular bundle.Whenmelon plants were treated under 9℃in night for 12 d,five vascular bundles in inner werebig,while five vascular bundles in inner circle were smaller than control.These changes canmake against sugar transport.Moreover,12℃in night did not affact the development ofvascular bundles.6.The ultrastructure of inner phloem of melon under condition of different nighttemperature were observed using TEM.The results showed that 9℃and 12℃in nightchanged ultrastructure of inner phloem on different degree.In detail,plasmalemmainvagination appeared in common companion cells and intermediary cells.Mitochondrianumber decreased steadily,the arrangement direction of grana changed,chloroplasts lamellawas blurry and multivesicular structures increased in common companion cells.A large ofstach grains appeared in phloem parenchyma cells and the character of nacreous wall wasmore obvious than control.Althrough these changes were related to cold acclimation,deleterious to sugar transport.7.It was found that the treatment of 9℃in night led to sugar accumulation in vascularbundles of side branches and fruit stem.The contents of fructose and raffinose were higher than control after treatment for 3 d,while the increase of glucose,sucrose and stachyoseoccured after treatment for 9 d in vascular bundles of side branches.The content of galactinoldrcreased compared with control,yet other carbohydrates were opposite in vascular bundlesof fruit stem.What was more,the amount of accumulated sugar in vascular bundles of fruitstem was more than that in vascular bundles of side branches,in paticular sucrose,suggestingthat the restriction degree of sugar transport in vascular bundles of fruit stem may be biggerthan vascular bundles of fruit stem and further verification was obtained that vascular bundlesof fruit stem may be more sensitive to low temperature.After treatment of 12℃in night for 6d,the content of galactinol was lower than control in vascular bundles of side branches andother carbohydrate had no change.Meanwhile,the contents of glucose,fructose and raffmosewere higher than control with significant difference at the end of treatment and othercarbohydrate had no change in vascular bundles of fruit stem.8.It was found that the sink strength was affected by different night low temperature ondifferent degree,especially 9℃in night.The factors related to sink strength were sugar-metabolizing enzymes activities,endogenous hormone and polyamine contents.The changeof sugar-metabolizing enzymes activities in fruit indicated that acid invertase（AI）,netutralinvertase（NI）andα-galactosidase activities enhanced,but sucrose synthase（SS）activities andsucrose phosphate synthase（SPS）activities declined with extraodinary significant differenceafter treatment of 9℃in night.What was more,the effects of 12℃in night onsugar-metabolizing enzymes activities was small,with no significant difference.9.The content of endogenous hormone had a great change after treatment of night lowtemperature.After the treatment of 9℃in night,GA₃,ZT and IAA reduced in evidence.GA₃/ABA and ZT/ABA was also reduced significantly,and ABA increased in the last stage offruit enlarging period with the extraordinary significant difference,but after the treatment of12℃in night,GA3,IAA and ABA added until the later of fruit enlarging period.In addition,the analysis of the relationship between fruit endogenous hormone and the increment rate ofsingle fruit indicated that whether treatments or control,there exists extreme positivesignificant linear relationship between GA₃/ABA and increment rate of single fruit,withdetermination coefficient bigger.However,except for control,there was no significant linearrelationship between ZT/ABA and increment rate of single fruit.10.The effect of different night low temperature on polyamine content in melon fruitwas observed in this paper.The contents of total PA,Spd and Put decreased at the beginningof treatment of 9℃in night,and the content of Spm reduced overall.Moreover,the contentof Put was lower than control with significant difference at the beginning of treatment of 12℃in night,whereas Spd and total PA were almost invariable.From the analysis of relatinshipbetween polyamine and increment rate of single fruit,it was indicated that the contents of Put,Spd and total PA contents in fruit were positively correlated to fruit enlarging.更多还原