摘 " "要:【目的】中華獼猴桃金奉果皮極薄,在生產(chǎn)中極易因碰傷、擦傷而導(dǎo)致果實(shí)受損,非常不利于貯藏和長(zhǎng)距離運(yùn)輸。通過(guò)植物生長(zhǎng)調(diào)節(jié)劑和礦質(zhì)元素處理,以期篩選出適宜金奉獼猴桃果皮增厚和提高果實(shí)品質(zhì)的有效處理措施。【方法】使用不同種類和不同質(zhì)量濃度的植物生長(zhǎng)調(diào)節(jié)劑和礦質(zhì)元素的處理組合,對(duì)金奉獼猴桃幼果進(jìn)行浸果或葉面噴施處理,檢測(cè)處理后的金奉獼猴桃果實(shí)品質(zhì)、果實(shí)解剖結(jié)構(gòu)和果皮細(xì)胞壁代謝相關(guān)酶活性的變化情況?!窘Y(jié)果】不同處理均顯著增加了果實(shí)的縱徑和單果質(zhì)量,且對(duì)果實(shí)內(nèi)在品質(zhì)有不同程度的改善效果。100 mg·L-1 GA3 + 5 g·L-1 CaCl2處理組合的果實(shí)品質(zhì)最佳,但對(duì)果皮厚度改善的效果并不明顯。不同質(zhì)量濃度的6-BA和NAA處理均顯著增加了外果皮厚度。其中,25 mg·L-1 NAA葉面噴施處理、25 mg·L-1 和50 mg·L-1 6-BA浸果處理對(duì)金奉獼猴桃外果皮增厚的效果最為顯著?!窘Y(jié)論】綜合各處理對(duì)金奉獼猴桃果實(shí)品質(zhì)和果皮厚度的影響,以及操作技術(shù)的簡(jiǎn)單易行,確定25 mg·L-1 NAA葉面噴施為最佳的處理。
關(guān)鍵詞:金奉獼猴桃;植物生長(zhǎng)調(diào)節(jié)劑;果實(shí)品質(zhì);果皮厚度;NAA
中圖分類號(hào):S663.4 文獻(xiàn)標(biāo)志碼:A 文章編號(hào):1009-9980(2025)01-0123-10
Effects of plant growth regulators on fruit quality and peel thickness of Jinfeng kiwifruit
TAO Junjie1, CHEN Shuangshuang1, 2, ZHONG Wenqi1, WU Mengting1, HUANG Lihong1, HUANG Yi-qian1, XU Yi1, HUANG Chunhui1*
(1College of Agronomy, Jiangxi Agricultural University, Nanchang 330045, Jiangxi, China; 2Fruit Tree Technology Extension Station of Huangyan District, Taizhou 318020, Zhejiang, China)
Abstract: 【Objective】 Kiwifruit is a berry with pericarp that can be divided into exocarp, mesocarp, and endocarp. The exocarp, known as the peel, protects the flesh from the adverse external environment and plays an important role in maintaining the hardness of the fruit and moisture in the fruit. Jinfeng kiwifruit (also known as Fenghuang No. 1) is a new yellow-fleshed kiwifruit cultivar selected from the seedlings of Actinidia chinensis. It has the comprehensive advantages such strong vigor, large single fruit weight, uniform fruit shape, delicate flesh, and high sugar and dry matter contents. This cultivar is a medium-to-late cultivar. It has the characteristics of strong adaptability, good stress resistance, high quality, and high yield. However, the peel of this cultivar is extremely thin and prone to bruises, abrasions, scratches, etc., which is very unfavorable for storage and long-distance transportation and thus limits the production and sales of the cultivar. In this study, plant growth regulators and mineral elements were used to treat the young fruit of Jinfeng, to screen out the effective treatment measures suitable for thickening the peel and improving the fruit quality of Jinfeng kiwifruit and provide technical support for its application. 【Methods】 Three plant growth regulators, 6-BA (6-benzylaminopurine, at 25 mg·L-1, 50 mg·L-1 or 75 mg·L-1), GA3 (gibberellic acid, at 50 mg·L-1 or 100 mg·L-1), and NAA (naphthylacetic acid, at 25 mg·L-1 or 50 mg·L-1) were selected. At the same time, different concentrations and combinations of CaCl2 and Zn (NO3)2 were also applied, and the treatments were divided into two types: fruit soaking and foliar spraying. For fruit soaking treatments, the fruit was completely soaked in the treatment solutions for at least three seconds 15 days after full bloom to ensure that the entire fruit surface was wetted. Three trees with basically the same vigor were selected for each treatment, and at least 50 fruit were randomly treated for each tree. For foliar spraying treatment, a sprayer was used to spray the leaves of the test trees at 15, 25, and 35 days after full bloom until both sides of the leaves were dripping. After the fruit reached the commercial maturity (soluble solids content ≥ 8%), at least 30 fruit of the same size and free of diseases and pests were picked for each treatment. The fruit were brought back to the laboratory immediately after harvest, and the fruit appearance indexes (transverse diameter, longitudinal diameter, single fruit weight, and fruit shape index) were measured. After the fruit placed at room temperature reached the edible state (soluble solids content ≥ 17.5%), the internal quality indexes of the fruit were determined. The soluble solid content was determined by a handheld digital sugar meter. The soluble sugar content was determined by anthrone colorimetry, and the total content of titratable acid was determined by the NaOH neutralization titration method. The content of ascorbic acid was determined by molybdenum blue colorimetry. The dry matter content of the fruit was determined by the drying method. The peel at the equatorial part of the fruit was fixed with FAA (alcohol formalin acetate mixed fixative solution), stained with the saffron solid green, and then observed and photographed with an upright white light photographing microscope. The number of epidermal cell layers, epidermal thickness, length and width of the peel cells were measured with the Image-Pro Plus 6.0 software. Finally, the activities of enzymes related to cell wall metabolism, including phenylalanine ammonialyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), cellulase, and pectinase, were measured. SPSS 22.0 was used for analyses of difference significance and correlation. Origin 2018 was used for graph drawing. 【Results】 All the treatments increased the length and single fruit weight of Jinfeng kiwifruit. The average single fruit weight in the foliar treatment of 1 g·L-1 Zn (NO3)2 + 25 mg·L-1 NAA was the highest. Saffron solid green staining showed that the main component of the peel of Jinfeng is lignin. Paraffin section observation showed that different plant growth regulator treatments significantly increased the thickness of Jinfeng kiwifruit peel, among which 25 mg·L-1 NAA foliar spray treatment, and 25 mg·L-1 and 50 mg·L-1 6-BA fruit soaking treatments had the most significant effect on the thickening of Jinfeng kiwifruit peel. The combination of 100 mg·L-1 GA3 + 5 g·L-1 CaCl2 treatment had the best fruit quality, but the effect in improving peel thickness was not obvious. The storage time of Jinfeng kiwifruit treated with 25 mg·L-1 NAA was significantly prolonged with the increase of peel thickness. 【Conclusion】 Based on the effects of each treatment on fruit quality and peel thickness of Jinfeng kiwifruit, as well as the simplicity of operation technique, 25 mg·L-1 NAA foliar spray is the best treatment.
Key words: Jinfeng kiwifruit; Plant growth regulators; Fruit quality; Peel thickness; NAA
獼猴桃隸屬獼猴桃科(Actinidiaceae)獼猴桃屬(Actinidia Lindl.),為多年生功能性雌雄異株木質(zhì)藤本植物[1]。獼猴桃果實(shí)營(yíng)養(yǎng)價(jià)值高,風(fēng)味獨(dú)特,富含糖、酸、酚類、氨基酸和維生素,尤其以富含維生素C而聞名。獼猴桃根、莖、葉、花中富含獼猴桃堿等多種生物活性成分,是一種藥食同源的食物,具有很高的綜合開發(fā)利用價(jià)值[1]。獼猴桃果實(shí)為漿果,果皮可分為外果皮、中果皮和內(nèi)果皮三部分。其中,外果皮即通常所說(shuō)的果皮,將果肉和外界環(huán)境分隔開,起到保護(hù)果實(shí)、保持水分、防止病菌侵害等作用[2]。獼猴桃外果皮通常較薄,這使其在生長(zhǎng)過(guò)程中易遭受風(fēng)吹擦傷、日曬灼傷及刺吸式害蟲叮傷,導(dǎo)致果實(shí)表面疤痕累累,不利于果實(shí)采后貯藏和運(yùn)輸,增加了果實(shí)損耗,降低了果實(shí)的商品價(jià)值。
植物生長(zhǎng)調(diào)節(jié)劑在果實(shí)生產(chǎn)中被廣泛使用,從而達(dá)到增厚果皮、改善果實(shí)品質(zhì)及防止果實(shí)開裂等目的。資陽(yáng)香橙砧清見雜柑果皮厚度的差異是IAA、GA3、ZT及其代謝相關(guān)酶活性和基因表達(dá)共同作用的結(jié)果。在一定范圍內(nèi),IAA、GA3和ZT含量越高,合成相關(guān)酶活性和基因表達(dá)量越高,果皮生長(zhǎng)發(fā)育程度越高,果皮越厚[3]。在荔枝果實(shí)發(fā)育早期進(jìn)行細(xì)胞分裂素處理,可降低果實(shí)采后失水和果皮褐變,延長(zhǎng)荔枝果實(shí)的貯藏期[4]。外源ABA和CaCl2處理櫻桃果實(shí),可顯著降低櫻桃果實(shí)開裂,顯著提高果實(shí)表面的蠟質(zhì)含量、角質(zhì)層和表皮厚度[5]。外源GA3處理可以有效地降低柑橘裂果的發(fā)生率,而不會(huì)顯著影響果實(shí)品質(zhì)[6]。IAA有很強(qiáng)的吸引與調(diào)運(yùn)養(yǎng)分的效應(yīng),葉面噴施IAA能顯著增加秋葵植株的高度、枝條數(shù)、葉片數(shù)、花朵數(shù)、果實(shí)質(zhì)量和果實(shí)中可溶性固形物含量[7],IAA處理也可使辣椒幼果迅速膨大并增加產(chǎn)量[8]。
金奉(曾用名奉黃1號(hào))獼猴桃是從中華獼猴桃金豐實(shí)生后代中選育而來(lái)的黃肉獼猴桃新品種,具有生長(zhǎng)勢(shì)強(qiáng)、單果質(zhì)量大、果形均勻一致、果肉金黃、肉質(zhì)細(xì)膩、含糖量高、干物質(zhì)含量高等綜合優(yōu)勢(shì)[9]。該品種在江西省宜春市奉新縣地區(qū)為中晚熟黃肉獼猴桃,在當(dāng)?shù)卦耘啾憩F(xiàn)出適應(yīng)性和抗逆性強(qiáng)、優(yōu)質(zhì)、豐產(chǎn)等特點(diǎn)。然而,生產(chǎn)中發(fā)現(xiàn)該品種果皮極薄,極易發(fā)生碰傷、擦傷、刮傷等,非常不利于貯藏和長(zhǎng)距離運(yùn)輸,對(duì)生產(chǎn)和銷售造成了極大的影響,在一定程度上影響了該品種的推廣[9]。為了改善金奉獼猴桃果皮薄的狀況,筆者在本研究中選用多種植物生長(zhǎng)調(diào)節(jié)劑和礦質(zhì)元素,進(jìn)行了不同種類、不同質(zhì)量濃度和不同組合的處理,通過(guò)檢測(cè)處理后的金奉獼猴桃果實(shí)品質(zhì)、果實(shí)解剖結(jié)構(gòu)和果皮細(xì)胞壁代謝相關(guān)酶活性的變化情況,篩選出有利于金奉獼猴桃果皮增厚和提高果實(shí)品質(zhì)的有效措施,為其推廣應(yīng)用提供技術(shù)支撐。
1 材料和方法
1.1 試驗(yàn)材料
以中華獼猴桃品種金奉為試材。該品種種植在江西省奉新縣新西藍(lán)現(xiàn)代農(nóng)業(yè)示范園,嫁接于美味獼猴桃金魁砧木上,樹齡6 a(年)。栽培架式為大棚架,常規(guī)管理。選用6-芐氨基嘌呤(6-BA)、赤霉素(GA3)和萘乙酸(NAA)三種植物生長(zhǎng)調(diào)節(jié)劑,質(zhì)量濃度設(shè)置如下:6-BA質(zhì)量濃度分別為25、50和75 mg·L-1;GA3質(zhì)量濃度分別為50和100 mg·L-1;NAA質(zhì)量濃度分別為25和50 mg·L-1。植物生長(zhǎng)調(diào)節(jié)劑處理的同時(shí)亦進(jìn)行了CaCl2和Zn(NO3)2不同質(zhì)量濃度、不同組合的處理。處理分為浸果和葉面噴施兩種,具體處理組合和處理方式詳見表1。對(duì)于浸果處理,于盛花后15 d將果實(shí)完全浸沒(méi)在處理液中至少3 s,以確保整個(gè)果面濕透。每個(gè)處理選擇生長(zhǎng)勢(shì)基本一致的3株樹,每株樹隨機(jī)選擇50個(gè)主花果進(jìn)行浸果處理。對(duì)于葉面噴施處理,則于盛花后15、25、35 d分別使用農(nóng)用噴霧器對(duì)試驗(yàn)樹進(jìn)行葉面噴施,需噴至葉片正反兩面滴水。每個(gè)處理均選擇生長(zhǎng)勢(shì)基本一致的3株樹。以清水浸果或噴施處理作為對(duì)照(CK)。果實(shí)達(dá)到商業(yè)采摘期[可溶性固形物含量(w,后同) ≥ 8%]后采摘,每個(gè)處理和對(duì)照各采摘至少30個(gè)大小一致、無(wú)病蟲害的果實(shí)。采后立即運(yùn)回實(shí)驗(yàn)室,并進(jìn)行果實(shí)外觀品質(zhì)指標(biāo)的檢測(cè)。果實(shí)室溫放置達(dá)到可食狀態(tài)(可溶性固形物含量 ≥ 17.5%)后進(jìn)行果實(shí)內(nèi)在品質(zhì)指標(biāo)的測(cè)定。
1.2 果實(shí)外觀品質(zhì)測(cè)定
每個(gè)處理每次重復(fù)隨機(jī)選擇10個(gè)果實(shí),使用千分之一電子天平測(cè)定單果質(zhì)量。使用數(shù)顯游標(biāo)卡尺測(cè)量果實(shí)的橫徑、縱徑,并計(jì)算出果形指數(shù)。
1.3 果實(shí)內(nèi)在品質(zhì)測(cè)定
采用手持式數(shù)顯糖度計(jì)(ATAGO,PAL-1)測(cè)定可溶性固形物含量。采用蒽酮比色法測(cè)定可溶性糖含量,采用NaOH中和滴定法測(cè)定果實(shí)可滴定酸總含量[10];采用鉬藍(lán)比色法測(cè)定抗壞血酸含量[11]。采用烘干法測(cè)定果實(shí)干物質(zhì)含量,即在獼猴桃果實(shí)赤道部位切取約2 mm厚的帶皮薄片,放置于60 ℃的恒溫干燥箱內(nèi)烘干至恒質(zhì)量,干質(zhì)量與鮮質(zhì)量的比值即為干物質(zhì)含量。
1.4 果皮石蠟切片制作
取果實(shí)赤道部位的果皮,切成0.3~0.5 cm長(zhǎng)寬的長(zhǎng)方形,用FAA(乙醇醋酸福爾馬林混合固定液,按90 mL 70%乙醇 + 5 mL冰醋酸 + 5 mL甲醛的比例配制)進(jìn)行固定,采用番紅-固綠染色法進(jìn)行染色觀察,然后用正置白光拍照顯微鏡(Nikon,Eclipse Ci-L)進(jìn)行觀察拍照。采用Image-Pro Plus6.0軟件進(jìn)行圖片測(cè)量分析,在垂直果實(shí)表面的軸線上測(cè)量表皮厚度,并測(cè)量表皮細(xì)胞的長(zhǎng)徑和短徑。
1.5 果皮細(xì)胞壁代謝相關(guān)酶活性測(cè)定
苯丙氨酸解氨酶(phenylalanine ammonia-lyase,PAL)活性參考高俊鳳[11]的方法測(cè)定;過(guò)氧化物酶(peroxidase,POD)活性采用愈創(chuàng)木酚法[12]測(cè)定;多酚氧化酶(polyphenol oxidase,PPO)活性采用鄰苯二酚法[13]測(cè)定;纖維素酶(cellulase)和果膠酶(pectinase)活性測(cè)定分別采用酶聯(lián)免疫分析(ELISA)試劑盒A138和A140-1-1(南京建成生物工程研究所)進(jìn)行,具體測(cè)定步驟參照試劑盒使用說(shuō)明書。
1.6 數(shù)據(jù)分析
使用Microsoft Excel 2020進(jìn)行數(shù)據(jù)整理。使用SPSS 22.0軟件進(jìn)行單因素方差分析(one-way ANOVA),采用Duncan’s多重極差檢驗(yàn)進(jìn)行樣本間差異顯著性分析(p<0.05)。利用Origin 2018進(jìn)行繪圖。
2 結(jié)果與分析
2.1 不同處理對(duì)金奉獼猴桃果實(shí)外在品質(zhì)的影響
利用不同種類、不同質(zhì)量濃度的植物生長(zhǎng)調(diào)節(jié)劑和礦質(zhì)元素的處理組合對(duì)金奉獼猴桃果實(shí)進(jìn)行處理,外在品質(zhì)指標(biāo)變化結(jié)果如表2所示。除T9處理外,其他處理果實(shí)的橫徑均顯著大于對(duì)照,其中T12處理的橫徑數(shù)值最大,達(dá)到58.11 mm,與CK相比增加了24.48%。所有處理均促進(jìn)了果實(shí)縱徑和單果質(zhì)量的增加,其中T12的單果質(zhì)量達(dá)到最大值,為147.50 g,與CK相比升高了83.68%;T4、T9處理的果形指數(shù)與CK差異顯著,其余處理與CK之間無(wú)顯著差異。
2.2 不同處理對(duì)金奉獼猴桃果實(shí)內(nèi)在品質(zhì)的影響
不同植物生長(zhǎng)調(diào)節(jié)劑和礦質(zhì)元素處理后金奉獼猴桃果實(shí)內(nèi)在品質(zhì)的變化情況如表3所示。結(jié)果表明,所有樣品的可溶性固形物含量在14.6%~18.1%之間,其中T3和T6的可溶性固形物含量與CK無(wú)顯著差異,其余處理均顯著低于CK。干物質(zhì)含量方面,T3干物質(zhì)含量最高,其次為CK。T1、T6、T9與CK之間無(wú)顯著差異,其余處理均顯著低于CK。所有樣品的可滴定酸含量在0.96%~1.19%之間,其中T12最高,且顯著高于CK,其他處理的可滴定酸含量均顯著低于CK,T4和T6的可滴定酸含量最低。糖酸比是影響口感的重要因素,T4的糖酸比值最高,達(dá)到13.42。T5、T12與CK無(wú)顯著差異,T8、T9和T11糖酸比顯著低于CK。所有樣品的抗壞血酸含量在97.84~119.82 mg·100 g-1之間,T3、T6處理的抗壞血酸含量最高,分別為119.82、119.12 mg·100 g-1,T4、T5、T7、T8處理抗壞血酸含量均顯著高于CK,其余處理的抗壞血酸含量與CK無(wú)顯著差異。
2.3 不同處理對(duì)金奉獼猴桃果皮解剖結(jié)構(gòu)的影響
金奉獼猴桃果皮石蠟切片如圖1所示。番紅可使木質(zhì)化細(xì)胞壁呈現(xiàn)紅色,角質(zhì)化細(xì)胞壁呈現(xiàn)透明粉紅色,固綠使細(xì)胞質(zhì)和含有纖維素的細(xì)胞壁呈藍(lán)綠色。金奉獼猴桃果皮外部細(xì)胞層結(jié)構(gòu)是由幾層壓縮放射狀排列的死細(xì)胞組成。這些死細(xì)胞全部被番紅染為紅色,證明其主要成分為木質(zhì)素。死細(xì)胞層下面是厚壁組織,由兩到三層排列緊密的放射狀壓縮細(xì)胞構(gòu)成。與厚壁組織相鄰的是薄壁細(xì)胞,薄壁細(xì)胞富含淀粉,更為細(xì)長(zhǎng),呈放射狀扁平,相比于厚壁組織排列較為疏松,近七八層薄壁細(xì)胞的大小和形狀基本一致。此外,在這一區(qū)域還散布著體積較大的石細(xì)胞。
不同處理的金奉外果皮厚度具有較大差異(圖2-A)。T1~T3為不同質(zhì)量濃度的6-BA處理,其外果皮厚度隨試劑質(zhì)量濃度的增加而下降,T10、T11為不同質(zhì)量濃度的NAA處理,存在同樣的規(guī)律。T4~T9、T13與CK之間無(wú)顯著差異,其余處理的外果皮厚度較CK均有顯著增加(圖2-A)。
表皮細(xì)胞的長(zhǎng)短徑受不同處理影響較?。▓D2-B、C)。T13的表皮層細(xì)胞長(zhǎng)徑最長(zhǎng),其次為T11,均顯著高于其他處理。T5的表皮細(xì)胞長(zhǎng)徑最短,顯著小于CK。其余處理與CK無(wú)顯著差異。T6、T7、T11、T12處理的表皮層細(xì)胞短徑均顯著高于CK,其余處理與CK無(wú)顯著差異(圖2-C)。不同處理對(duì)表皮細(xì)胞面積的影響也較小,除T11、T13處理外,其余處理與CK不存在顯著差異(圖2-D)。
2.4 不同處理對(duì)金奉獼猴桃果皮細(xì)胞壁代謝相關(guān)酶活性的影響
不同處理對(duì)金奉獼猴桃果皮細(xì)胞壁相關(guān)代謝酶活性的影響如圖3所示。不同處理均不同程度地降低了PAL的活性(圖3-A)。CK的PAL活性最高,其次為T9處理,T13的PAL活性最低,約為CK的46%(圖3-A)。不同處理間POD活性變化較大(圖3-B)。T3、T10~T12處理具有較高的POD酶活性,約為CK的1.5倍,T8、T9的POD活性較低,約為CK的60%,并顯著低于所有處理,T4~T7、T13與CK之間無(wú)顯著差異(圖3-B)。不同處理間PPO活性差異明顯(圖3-C)。T10的PPO活性最高,而T1、T3、T4、T6的PPO活性最低,且顯著低于其他所有處理。T9、T11與CK之間無(wú)顯著差異。T6的果膠酶活性與CK無(wú)顯著差異,T7~T9、T11、T13的果膠酶活性顯著低于CK,其余處理的果膠酶活性均顯著高于CK(圖3-D)。T4的纖維素酶活性顯著高于CK和其他處理,T1、T3、T5、T6、T8、T10等與CK無(wú)顯著差異,T2、T7、T12顯著低于CK,其中T7的纖維素酶活性最低(圖3-E)。
3 討 論
筆者在本研究中針對(duì)金奉獼猴桃果皮較薄的問(wèn)題,主要應(yīng)用植物生長(zhǎng)調(diào)節(jié)劑和礦質(zhì)元素進(jìn)行不同質(zhì)量濃度、不同方式的處理,通過(guò)測(cè)定果實(shí)品質(zhì)、細(xì)胞壁代謝酶活性,果皮解剖結(jié)構(gòu)觀察進(jìn)行比較分析,以期篩選出促進(jìn)金奉獼猴桃果皮增厚和果實(shí)品質(zhì)提升的最佳處理。
生長(zhǎng)素能刺激細(xì)胞壁合成、細(xì)胞擴(kuò)大和細(xì)胞分裂,對(duì)延緩葉片衰老和果實(shí)成熟有著重要的作用。噴施IAA能顯著提高花生葉片光合速率,促進(jìn)莖、穗和花的生長(zhǎng),最終提高花生平均單莢質(zhì)量和單株產(chǎn)量[14]。在番茄[15]、梨[16]、藍(lán)莓[17]和草莓[18]等植物上的研究表明,適宜濃度的NAA對(duì)促進(jìn)果實(shí)發(fā)育和膨大、防止落果、提高果實(shí)品質(zhì)等具有顯著的效果。筆者在本研究中使用不同質(zhì)量濃度的NAA噴施金奉獼猴桃,結(jié)果顯示NAA處理后果實(shí)單果質(zhì)量顯著增加,表明NAA有很強(qiáng)的吸引與調(diào)運(yùn)養(yǎng)分的效應(yīng),能使果實(shí)幼期迅速膨大,增加產(chǎn)量。NAA處理的獼猴桃果實(shí)可滴定酸含量顯著降低,而抗壞血酸含量與CK無(wú)顯著差異,表明NAA在提升金奉獼猴桃產(chǎn)量的同時(shí),其營(yíng)養(yǎng)價(jià)值未受明顯影響。PAL是催化苯丙氨酸合成途徑的第一步,被認(rèn)為是控制植物木質(zhì)素積累的關(guān)鍵起始酶[19]。POD由多基因編碼且定位在細(xì)胞壁上,參與植物木質(zhì)素的生物合成、細(xì)胞伸長(zhǎng)、脅迫防御和種子萌發(fā)等多種生物過(guò)程[20-21]。使用不同質(zhì)量濃度NAA處理后,獼猴桃果皮中PAL活性顯著低于CK,而POD活性卻顯著高于CK。在煙草[22]和山楊[23]中的研究表明,木質(zhì)素含量隨POD活性降低而顯著降低。擬南芥POD編碼基因功能缺失突變體中木質(zhì)素含量也顯著減少[24]。在本研究中,施用不同質(zhì)量濃度NAA處理后獼猴桃果皮中POD活性均顯著高于CK,而不同質(zhì)量濃度的NAA處理均顯著增加了獼猴桃表皮死細(xì)胞層的厚度,這表明POD可能參與了獼猴桃表皮細(xì)胞木質(zhì)素合成的調(diào)控,與獼猴桃表皮細(xì)胞木質(zhì)素含量的積累相關(guān)。此外,在試驗(yàn)中筆者還發(fā)現(xiàn)NAA處理的果實(shí)在相同的室溫條件下比其他處理的果實(shí)推遲10~15 d變軟,這說(shuō)明NAA處理延緩了金奉果實(shí)的成熟,延長(zhǎng)了其軟熟時(shí)間。與CK相比,NAA處理的果實(shí)采后果腐病發(fā)生概率也較低,這表明NAA還提高了金奉獼猴桃果實(shí)的抗病性。
6-BA為人工合成的細(xì)胞分裂素類物質(zhì),能通過(guò)促進(jìn)細(xì)胞分裂維持新陳代謝與營(yíng)養(yǎng)物質(zhì)運(yùn)輸,改善果實(shí)品質(zhì),實(shí)現(xiàn)增產(chǎn)增收[25-26]。在本研究中,T1(25 mg·L-1 6-BA)、T2(50 mg·L-1 6-BA)、T3(75 mg·L-1 6-BA)處理均顯著增加了獼猴桃果實(shí)的單果質(zhì)量。此外,6-BA處理的果實(shí)品質(zhì)也得到一定的提升,如降低了果實(shí)可滴定酸含量,提高了果實(shí)可溶性糖含量,提高了糖酸比和抗壞血酸含量。6-BA處理顯著提高了POD酶活性,且該酶活性隨6-BA質(zhì)量濃度的增加而升高。施用不同質(zhì)量濃度的6-BA均顯著增加了外果皮厚度,表明6-BA處理可促進(jìn)木質(zhì)素含量的積累和果皮增厚。
GA3是一種高效的植物生長(zhǎng)調(diào)節(jié)劑,具有促進(jìn)細(xì)胞、莖伸長(zhǎng),打破種子休眠,促進(jìn)果實(shí)生長(zhǎng)發(fā)育的作用。外源赤霉素能夠促進(jìn)梨的花梗發(fā)育,特別是加速木質(zhì)部和韌皮部組織的增大,進(jìn)而增加梨果實(shí)的大小[27]。外源GA3處理可有效抑制棗果皮細(xì)胞壁水解酶活性,從而影響果皮原果膠、纖維素含量,最終增強(qiáng)了果皮的破裂應(yīng)力,降低了裂果率[28]。外源施用適宜濃度的GA3處理可促進(jìn)菠蘿果實(shí)膨大、提高果實(shí)質(zhì)量和改善果實(shí)品質(zhì)[29]。在本研究中,不同質(zhì)量濃度的GA3(T4和T5)處理均顯著增加了獼猴桃果實(shí)的單果質(zhì)量,說(shuō)明GA3可促進(jìn)營(yíng)養(yǎng)物質(zhì)向果實(shí)的轉(zhuǎn)運(yùn)。較低質(zhì)量濃度的GA3處理可顯著降低果實(shí)可滴定酸含量,增加果實(shí)可溶性糖含量、糖酸比和抗壞血酸含量,明顯地改善果實(shí)的內(nèi)在品質(zhì)指標(biāo),但是對(duì)外果皮厚度影響不大。
T6(100 mg·L-1 GA3 + 5 g·L-1 CaCl2)、T7(50 mg·L-1 GA3 + 50 mg·L-1 NAA)、T12(1 g·L-1 Zn(NO3)2 + 25 mg·L-1 NAA)、T13(5 g·L-1 CaCl2 + 25 mg·L-1 NAA)為植物生長(zhǎng)調(diào)節(jié)劑的組合處理。這些處理組合均能顯著增加果實(shí)單果質(zhì)量,其中T6的可溶性固形物以及干物質(zhì)含量與CK無(wú)顯著差異;T12處理的糖酸比與CK無(wú)顯著差異,其余處理均顯著增加了果實(shí)的糖酸比;抗壞血酸含量方面,T6、T7較CK有顯著提升。IAA、GA3以及6-BA無(wú)論是單獨(dú)處理還是混合處理,均能提高獼猴桃的產(chǎn)量,尤其是T6處理,在增加產(chǎn)量的前提下,顯著提高獼猴桃果實(shí)的各項(xiàng)內(nèi)在品質(zhì)指標(biāo)。果皮解剖結(jié)構(gòu)觀測(cè)顯示,除T12處理外,其余混合處理不能明顯增加外果皮的厚度。4個(gè)組合處理明顯降低了苯丙氨酸解氨酶活性;T12的POD酶活性顯著高于CK,其余處理POD活性與CK無(wú)顯著差異;T12的PPO酶活性顯著高于CK,其余處理PPO活性顯著低于CK;T6的果膠酶與CK無(wú)顯著差異,T12的果膠酶活性顯著高于CK,其余處理均顯著降低果膠酶活性;T6的纖維素酶活性與CK無(wú)顯著差異,其余處理的纖維素酶活性顯著低于CK。
鈣是細(xì)胞壁的重要組成成分,主要在細(xì)胞壁的胞間層沉積,在維持細(xì)胞壁的完整性中起著重要作用[30]。噴施不同濃度的CaCl2溶液均顯著增加了果實(shí)的單果質(zhì)量,而未影響果實(shí)品質(zhì)。CaCl2處理的PAL、POD和果膠酶活性均顯著降低。鈣處理使南果梨木質(zhì)素及其前體羥基肉桂酸類物質(zhì)的含量顯著降低,木質(zhì)素合成相關(guān)基因的表達(dá)水平也明顯下調(diào),抑制了木質(zhì)素單體的合成[31]。在本研究中,CaCl2處理的外果皮厚度與CK之間無(wú)顯著差異,這可能是鈣處理抑制了木質(zhì)素的生成。
4 結(jié) 論
使用不同種類、不同質(zhì)量濃度和不同組合的植物生長(zhǎng)調(diào)節(jié)劑和礦質(zhì)元素處理金奉獼猴桃,結(jié)果表明,不同處理均顯著增加了果實(shí)的單果質(zhì)量,對(duì)果實(shí)品質(zhì)有不同程度的改善效果。其中,100 mg·L-1 GA3+ 5 g·L-1 CaCl2處理組合的果實(shí)品質(zhì)最佳,但對(duì)果皮厚度改善的效果并不明顯。不同質(zhì)量濃度的6-BA和NAA處理均顯著增加了外果皮厚度,其中,25 mg·L-1 NAA噴施處理、25 mg·L-1和50 mg·L-1 6-BA浸果處理對(duì)金奉獼猴桃外果皮增厚的效果最為顯著。綜合各處理對(duì)金奉獼猴桃果實(shí)品質(zhì)與外果皮厚度的影響,以及操作技術(shù)的簡(jiǎn)單易行,確定25 mg·L-1 NAA葉面噴施為最佳的處理。
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