【作者】 温明霞；

【导师】 石孝均；

【作者基本信息】 西南大学 ， 植物营养学， 2012， 博士

【摘要】 钙是柑橘(Citrus L.)生长的必需营养元素,是细胞壁及膜系统的构成成分,果实中钙含量的高低,决定着果实细胞的结构牢固性和膜系统的稳定性,与果实生理性病害的发生密切相关。重庆是柑橘生长的最适宜生态区之一,柑橘种植面积已达1.26×105hm2,柑橘产业已成为重庆三峡库区经济发展的支柱产业。但是重庆市柑橘裂果、油胞下陷等生理性病害问题突出,果实采后不耐贮藏,严重阻碍了柑橘产量、品质和经济效益的进一步提高。这些生理性病害的发生是否与钙素营养有关目前尚不清楚,国内外对落叶果树(苹果、梨等)的钙素营养进行了大量研究,对柑橘钙素营养的研究相对较少,在柑橘对钙的吸收及分配规律等方面尚未见报道；在钙与果实品质及生理性病害发生的关系上,大多是通过采后补钙来进行研究,缺乏在果实生长期补钙对果实内在品质及贮藏性影响的相关报道。因此,调查重庆市柑橘园的钙素营养现状,研究柑橘对钙的吸收及分配规律,弄清钙调控果实品质及生理性病害的潜在机制,对于改善柑橘钙素营养,减少裂果等生理性病害的发生,延长果实贮藏寿命,制定柑橘钙素优化管理措施等都具有重要意义。本文采用调查研究、田间试验、贮藏试验和采样分析相结合的方法,以重庆市主产区柑橘园为研究对象,开展柑橘园土壤、叶片钙营养现状的调查研究,分析土壤钙与叶片钙含量之间的关系以及不同品种间钙含量的差异,明确重庆市柑橘园钙素营养现状及影响因子,以期为重庆市柑橘园的钙素调控提供基础数据。以重庆市大面积栽培的鲜食品种锦橙(citrus sinensis Osbeck)为研究对象,通过在年生长周期内的不同发育阶段进行树体解析,来研究成龄柑橘树对钙的吸收及分配特征,明确柑橘对钙的需求规律,旨在为柑橘钙素的优化管理提供科学依据。以容易发生裂果的柑橘品种-锦橙为研究对象,开展正常果与裂果果实及营养母枝叶片养分含量的分析,明确影响柑橘裂果的关键因子；采用田间试验在花前及幼果期进行树体喷钙处理,研究钙对裂果、果皮结构物(果胶)及其水解酶类、活性氧清除酶类、多酚氧化酶(PPO)活性的影响,明确钙调控柑橘果实裂果的生理机制。在柑橘生长的不同时期进行树体补钙,研究钙对果实生长、果实品质及贮藏性的影响,探讨钙影响果实品质及贮藏性的生理机制,为合理调控柑橘园钙素营养、有效防止果实裂果和延长果实的贮藏保鲜期提供理论和技术支撑。通过对重庆市218个柑橘园土壤和叶片的采样分析,研究结果表明,重庆市柑橘园土壤钙含量丰富,平均为3316.7mg/kg,其中49.5%的土壤有效钙含量较高(>3000mg/kg),缺钙的土壤(<1000mg/kg)仅占17.9%；但是柑橘叶片钙含量(<30g/kg)低量或缺乏的柑橘园占38.3%,叶片钙含量(>70g/kg)过高的仅占0.3%；叶片钙含量不足的样本数明显高于缺钙土壤,说明土壤中充足的钙并不能完全保障柑橘对钙素营养的需求。土壤钙含量与土壤pH呈极显著正相关,随着土壤pH的降低,土壤有效钙含量呈降低趋势。长期施肥等人为因素加剧了土壤pH的变化,进而明显影响钙素含量。与背景样相比,重庆市84.6%的柑橘园土壤pH值呈下降趋势,平均降幅为9.6%,土壤pH值小于5.5的柑橘园明显增加,占调查总数的32.7%,在柑橘生产中应防止土壤酸化等造成土壤缺钙进而影响树体的钙素营养。土壤钙与柑橘叶片钙含量的关系因土壤钙含量的不同而存在差异,当土壤有效钙含量低(<1000mg/kg)时,叶片钙含量也低(<30g/kg),在此范围内叶片钙含量随土壤有效钙的增加而升高,二者呈极显著的正相关：y=0.0151x+16.459(r=0.608**, n=39, r0.01=0.408);当土壤有效钙含量在高量或过量范围时,二者的相关关系不显著,叶片缺乏和过量现象并存。说明缺钙土壤必然造成叶片钙营养不足,而钙含量高的土壤上也可能发生叶片缺钙现象,土壤施钙对叶片钙含量的提高作用是有限的。不同种类柑橘叶片钙含量差异较大,其中以脐橙最高,锦橙最低,主要与树体本身的遗传特性及对养分的吸收利用不同有关；不同种植区柑橘园叶片钙含量平均为32.7g/kg,除永川和江津低于适宜范围外,其它各地均处于适宜范围；叶片钙含量与镁呈极显著正相关,与氮、磷、钾、铁、锰呈显著负相关,与其它养分不相关。柑橘对钙吸收和分配的研究结果表明,年生长周期内,7年生的北碚447锦橙(Citrus sinensis Osbeck cv. Jinchen)树每株从土壤中吸收了119.4g钙,其中81.0%用于地上部的生长和消耗,19.0%用于根系的生长需求。果实膨大期和萌芽抽梢期是柑橘需钙最多的时期,这两个时期吸收的钙分别占全年吸钙总量的66.3%和32.7%,因此在这两个时期是补充树体钙素营养的关键期。成熟期柑橘树体中钙含量为：叶片>枝>根>果实,柑橘树体吸收的钙大部分贮藏于枝梢和叶片,枝、叶、根、果实的钙素累积量分别占整株钙累积总量的50.7%、25.0%、21.2%和3.1%,在不同枝梢中,主干为钙素的主要贮藏场所,成熟期果实的钙含量和累积量均表现为最低,是果实容易发生生理性病害的原因之一柑橘不同器官钙含量大小表现为：叶片钙含量高于枝条,1年生枝条钙含量高于多年生枝条；随着新生器官的生长,成龄枝梢的钙含量降低,而幼嫩器官钙含量呈增加趋势；枝梢皮层的钙含量远高于其木质部的钙含量,随着枝条的加粗变老,皮层钙含量和累积量逐渐增加,而木质部的钙含量则与之相反。柑橘不同器官在不同生长期对钙素的需求量不同,果实的主要需钙期在幼果期和果实膨大生长期；新生枝梢和根系对钙的吸收需求主要发生在萌芽抽梢期和果实膨大生长期；成龄枝梢的主要需钙期为果实膨大生长期。由于果实蒸腾力弱,根系吸收的钙难以到达果实,因此在幼果期和果实膨大生长期喷施钙是调控果实缺钙的关键措施。通过对北碚447锦橙果园的调查研究和采样分析,研究了裂果和正常果功能叶片、果皮和果肉中N、P、K、Ca含量及相关酶的活性,探讨了钙与锦橙裂果的关系及其生理机制。结果表明,裂果植株叶片和裂果果皮、果肉的钙含量均显著低于正常果,裂果率与果皮中的钙呈极显著的负相关；裂果果皮中多酚氧化酶(PPO)、多聚半乳糖醛酸酶(PG)、纤维素酶(CX)的活性较高,而过氧化氢酶(CAT)的活性较低；果实的裂果率与果皮中的PPO活性成显著正相关,与CAT活性和原果胶(PP)含量呈极显著的负相关。果皮中钙含量不足导致细胞壁水解酶(PG、CX)和PPO活性提高、维持果皮强度和延展性的原果胶含量降低是锦橙裂果发生的主要原因。喷钙处理显著降低了果皮中MDA的含量和PPO、POD、PG、CX活性,提高了SOD、CAT活性,果皮中原果胶的含量显著增加,提高了果皮的弹性和抗裂能力,从而降低了果实膨大生长期的裂果率。因此,在果实生长期补充钙是减少锦橙裂果的有效措施。柑橘生长期喷钙能显著增加果实钙含量,提高果实成熟时的Vc含量,并抑制果实贮藏过程中Vc等物质的氧化分解,提高果实可溶性固形物含量和糖酸比,改善果实风味和品质。在柑橘生长的不同时期喷钙均能提高果皮和果肉中抗氧化酶(CAT、SOD)活性,降低细胞壁水解酶(PG、CX)、过氧化物酶(POD)活性,减轻脂质过氧化程度,果胶的分解转化速度减慢,丙二醛、可溶性果胶的含量明显降低,从而维持果皮具有一定的强度,延缓了果实的衰老,降低烂果的发生率,延长了果实的贮藏保鲜期。其中以幼果期喷钙在提高果实钙含量、改善贮藏性等方面的效果最佳,其次是果实膨大生长期喷钙,成熟期喷钙效果最差。因此在幼果期和果实膨大生长期喷钙是改善柑橘钙素营养、减少柑橘果实裂果、提高果实品质、延长采后果实贮藏保鲜期的重要措施。更多还原

【Abstract】 Calcium (Ca), as an essential element for citrus growth, constituent of cell wall and membrane system, has important effects on yield and quality of citrus fruit. Ca concentration of fruit is closely related to cell structure soundness and membrane stability with the result that impacts physiological diseases of fruit. Chongqing is one of best regions to meet the need of citrus growth where the citrus area amounts to1.26×105hm2and citrus has been a mainstay industry for the development of Three Gorges reservoir area. But the physiological diseases such as fruit cracking and oleocellosis occurred frequently, the shelf life of citrus fruit after harvest was so short that hindered citrus yield increase and quality improvement. Whether these physiological diseases related to Ca nutrition has not been certain. Many researches have been carried out on Ca nutrition of fruit trees and mainly concentrated on Ca absorbed by deciduous fruit trees, for example, apple and pear, but few on Ca nutrition of citrus especially on Ca absorption, accumulation and distribution in citrus trees. The relation of Ca and fruit quality and physiological diseases was studied by Ca supplement after fruit harvested but few reported about the effect of Ca sprayed during fruit growth on the quality and storage property of fruit.Therefore, it is necessary to research Ca nutrition in Chongqing citrus orchards and the absorption and distribution of Ca in citrus trees to make clear the physiological mechanism of Ca on fruit quality and diseases so that prevent fruit from physiological diseases, prolong the storage time and propose comprehensive management measures.The study was carried out by investigation, field test, storage test and sampling determination. It was researched that nutrition concentration of soil and leaves in Chongqing citrus orchards to make clear Ca nutrition status, the relation of Ca and other nutrient elements, the differences of Ca nutrition among citrus cultivars to determine the important factors of Ca in citrus orchards and regulate Ca nutrition reasonably in Chongqing; Ca absorption and distribution in citrus tree was studied to propose basic data for regulating Ca nutrition of citrus by digging and separating Beibei447Jincheng orange (citrus sinensis Osbeck) trees cultivated7years under field condition into different parts in a growth cycle; Beibei447Jincheng orange was investigated to research the differences of N, P, K, Ca concentrations and enzyme activities in leaves, peel and pulp between cracked fruits and normal ones. The effect of calcium on pectin, malonaldehyde (MDA) and enzymes related to hydrolysis and reactive oxygen species clearing and polyphenol oxidase (PPO) of citrus peel were studied by spraying calcium nitrate before blossom and young fruit period on Beibei447Jincheng orange to determine the physiological mechanism of fruit cracking; The effects of Ca on growth, quality and storage property of fruit and its physiological mechanism were studied by spraying Ca on citrus trees in different growth periods to propose comprehensive management measures for Ca nutrition of citrus orchards.Ca in soil and leaves of218citrus orchards in Chongqing were studied and the results showed that there was abundant Ca in Chongqing citrus orchards with the average of3316.7mg/kg, soil Ca concentration in49.5%citrus orchards exceeded3000mg/kg belonging to excessive range and that in17.9%citrus orchards was less than1000mg/kg under the range of deficiency but Ca concentration of leaves in38.3%citrus orchards (<30g/kg) under the range of deficiency and that only in0.3%citrus orchards exceeded70g/kg belonging to excessive range, which signified that soil with abundant Ca did not ensure the need of citrus trees to Ca nutrition.Soil Ca concentration was significantly positive correlated to soil pH and decreased with the decrease of soil pH value. Long-term fertilization and other anthropic factors aggravated soil acidification and then impacted Ca concentration in soil. Soil pH decreased by9.6%in84.6%citrus orchards. Soil pH was below5.5in32.7%citrus orchards. Fertilization could be main cause of soil acidification in citrus orchards. Effective measures should be taken to protect citrus orchards soil from acidification to avoid Ca deficiency in soil and citrus trees.The relation of Ca concentration in soil and citrus leaves was not certain because of the change of Ca concentrations in soil. Under the low range of available Ca concentration in soil, Ca concentration in leaves increased with the increase of soil Ca concentration and they were significantly positive correlation:y=0.0151x+16.459(r=0.608**, n=39, ro.o1=0.408); When soil Ca concentration was in low or high range, it was not correlated to Ca concentration of leaves in deficient or excessive range. As a result, deficient Ca in soil must lead to Ca deficientcy in leaves but excessive Ca in soil could result in deficient Ca in leaves, it was limited to increase Ca concentration in leaves by Ca fertilized in soil.There were large differences among Ca concentration in leaves of different citrus varieties with highest Ca in Naval orange and lowest Ca in Jincheng orange leaves, which might be related to their own hereditary character of absorption to Ca. Ca concentration of leaves in Yongchuan and Jiangjin citrus orchard were lower than optimum range but those in other areas were in the range of 30-45g/kg. Ca concentration in citrus leaves was significantly positive related to Magnesium (Mg) but negatively correlated to nitrogen (N), phosphorus (P), potassium (K), ferrum (Fe) and manganese (Mn).It was studied that Ca absorption and distribution in citrus trees and the results showed that a citrus tree absorbed119.4g Ca from soil in a growth cycle, among of it81.0%for the growth of above ground part and19.0%for roots. The crucial periods of absorption to Ca were germination period and fruit rapid-growth period which the average of Ca accumulation was66.3%and32.7%respectively. Spraying Ca on citrus trees in the two periods could be regarded as an important measure to improve Ca nutrition of citrus trees. The order of Ca concentrations in different organs of citrus trees was:leaves>branches>roots>fruits. Most of Ca absorbed by citrus tree accumulated in branches and leaves and the percentage of Ca accumulated in roots, branches, leaves and fruits were21.2%,50.7%,25.0%and3.0%, respectively. Trunk was one of major organs of citrus trees to store Ca nutrition. The concentration and accumulation of Ca in fruits were both lower than other organs, which could be one of reasons physiological diseases occurred frequently in fruits.The Ca concentrations of citrus organs were different from each other, which of leaves were higher than those of branches and those of1-year-old branches were higher than those of adult ones. The Ca concentration of young shoots increased but adult branches decreased with the growth of new organs. The Ca concentrations in cortex of branches were well above those in xylem of branches. Ca concentrations and accumulation in cortex of branches increased with the increase of branch diameter but the concentration of xylem was the opposite. There were differences in Ca requirements among citrus organs. Fruits accumulated more Ca during young fruit period and fruit rapid-growth period than other periods; Branches accumulated Ca mainly in fruit rapid growth period. Ca absorbed by roots was difficult to transport to fruit because of its low transpiration. As a result, spraying Ca in citrus trees during young fruit period and fruit rapid-growth period could be crucial measures to regulating and controlling Ca deficiency in fruits.Beibei447Jincheng orange was investigated to research the differences of N, P, K, Ca concentrations and enzyme activities in leaves, peel and pulp between cracked fruits and normal ones to study the relation of Ca and fruit cracking and its physiological mechanism. The results showed that the concentrations of Cain leaves, peel and pulp of normal fruits were higher than those of cracked ones. Fruit cracking rate was negatively correlated to Ca concentration in citrus peel significantly. The activities of polyphenol (PPO), polygalacturonase (PG) and cellulase (CX) of cracked fruits were higher than those of normal ones, but those of catalase (CAT) were lower. Fruit cracking rate was positively correlated to PPO and negatively correlated to CAT and the concentration of protopectin (PP) significantly. The concentration of MDA, the activities of PPO, PG, CX of citrus peel in fruit rapid-growth period decreased by spraying calcium while the activities of superoxide dismutase (SOD), CAT and the concentration of protopectin (PP) increased significantly. Low concentration of Ca in citrus peel resulted in increase of activities of enzymes (PPO, PG and CX) in cell-wall metabolism. The low protopectin concentration that might maintain intensity and extensibility of citrus peel was the main cause for fruit cracking. Spraying calcium to citrus trees decreased fruit cracking rate and could be regarded as an important measure to prevent fruit cracking of Jincheng orange.Ca concentration and vitamin C (Vc) concentration in citrus fruits increased significantly, the oxygenolysis of Vc was restrained, total soluble solid (TSS), the ratio of sugar and acid increased and the edible flavour maintained during storage time by spraying Ca on citrus trees in different growth periods. The activities of polygalacturonase (PG) and cellulase (CX) decreased but those of superoxide dismutase (SOD), catalase (CAT) increased because of high Ca concentration in fruits. The structure of cell was protected and lipid peroxidation was alleviated so that malonaldehyde (MDA) and soluble pectin concentration decreased, the senescence of fruit postponed and eventually kept the fruit in good during storage time. Spraying Ca on citrus trees in young fruit period was the best way to keep citrus fruit in good property during storage time.更多还原