根冠關(guān)系對(duì)作物水分利用的調(diào)控

1、根冠關(guān)系對(duì)作物水分利用的調(diào)控博 士 生： 張歲岐學(xué)科專(zhuān)業(yè)名稱： 植物學(xué)研 究 方 向： 植物水分生理生態(tài) 指 導(dǎo) 教 師： 山侖研究員水分不足是干旱半干旱地區(qū)農(nóng)業(yè)生產(chǎn)的主要限制因子， 這種環(huán)境下的農(nóng)業(yè)生產(chǎn)必須以 水分的高 效利用為中心，為此，除采取工程、農(nóng)藝措施以減少農(nóng)田水分的徑流、蒸發(fā)、滲 漏損失外，提高作物 本身的水分利用效率（ WUE ）應(yīng)是實(shí)現(xiàn)作物高效用水的中心和潛力所 在。本研究以不同倍性的小麥進(jìn)化材料和不同玉米品種為材料，在盆栽、管栽和大田條件 下，就作物 根系行為（根系大小、分布、功能） 、根冠關(guān)系對(duì)其 WUE 的影響進(jìn)行了研究， 同時(shí)以玉米雜交種 戶單四號(hào)為材料在盆栽條件下就N

2、、 P 營(yíng)養(yǎng)影響作物根冠關(guān)系從而調(diào)控其 WUE 的機(jī)理進(jìn)行了研究。獲得如下主要結(jié)果：1玉米上，葉片水分狀況和根源 ABA 濃度共同控制玉米葉片的氣孔行為， 且根源 ABA 濃度 與氣孔阻力的關(guān)系更為密切， 木質(zhì)部汁液 pH 也在調(diào)控氣孔行為方面有作用， pH 值的 增加降低了 玉米葉片的氣孔開(kāi)度； 玉米根源 ABA 濃度與其葉片的光合和蒸騰速率成拋物線 關(guān)系，但由于光合 和蒸騰對(duì)根源 ABA 濃度反應(yīng)的敏感性區(qū)間存在差異，因而玉米的葉片 WUE 也與其根源 ABA 濃度 成顯著拋物線關(guān)系， 過(guò)高或過(guò)低的根源 ABA 濃度均會(huì)降低玉米 的葉片 WUE ；在可以長(zhǎng)期產(chǎn)生 ABA 的情況下，根源 A

3、BA 濃度與玉米產(chǎn)量和 WUE 成顯著 負(fù)相關(guān)關(guān)系，兩者均隨根源 ABA 濃度的增加 而降低，且以子粒產(chǎn)量計(jì)的 WUE 對(duì)根源 ABA 濃度的敏感性要大于以生物量計(jì)的 WUE 對(duì)根源 ABA 濃度的敏感性， 雖然根源 ABA 濃度對(duì) 地上部生長(zhǎng)的影響要大于對(duì)產(chǎn)量的影響； 玉米根系生長(zhǎng)與根 源 ABA 濃度也成顯著負(fù)相關(guān)關(guān) 系，但根、 冠生長(zhǎng)對(duì)根源 ABA 濃度的敏感性不同， 其對(duì)根系生長(zhǎng) 的擬制要小于對(duì)冠層生長(zhǎng) 的擬制。雜交種戶單四號(hào)由于在干旱下有相對(duì)較低的根源 ABA 濃度，因而 在葉片氣體交換 能力、生物量、產(chǎn)量和 WUE 上均高于其相應(yīng)親本，干旱下單葉 WUE 分別較兩個(gè) 親本高 38%

4、和 33% ，整株水平 WUE 分別高 25%和 17%。2根系水力導(dǎo)度 Lp 是反映根系吸水能力的重要水力學(xué)參數(shù)，玉米葉片的光合和蒸騰 速率均隨 其 Lp 的增加而線性增加， Lp 也與玉米葉片 WUE 成拋物線關(guān)系，過(guò)高或過(guò)低的 Lp 均會(huì)降低玉米 的葉片 WUE ，且這種關(guān)系存在品種間差異；而 Lp 與玉米生物量、產(chǎn)量 和 WUE 均成正相關(guān)關(guān)系， 隨 Lp 的增大而增加， 雜交種戶單四號(hào)與其親本相比有較高的根 系 Lp 。2n 6n 進(jìn)化過(guò)程中，小. 作物的根、冠大小對(duì)其水分利用有明顯調(diào)控作用，在小麥麥根系大小與其整株水平 WUE 成顯著負(fù)相關(guān)， WUE 隨根重的增大而減小，地上部生物

5、量 與其整 株水平 WUE 成拋物線關(guān)系， 過(guò)大或過(guò)小的冠部生長(zhǎng)均會(huì)降低小麥的整株水平 WUE ， 根冠比與其 WUE成負(fù)相關(guān)關(guān)系。這說(shuō)明在小麥從 2n八6n的進(jìn)化過(guò)程中，根系生長(zhǎng)存在著對(duì) WUE不利的冗余，而這種根系生長(zhǎng)的冗余隨染色體倍性的增加而減小，從而使其整株 水平 WUE 增大。 在玉米上， 根 重和生物量與其 WUE 成拋物線關(guān)系， 過(guò)大的根系生長(zhǎng)反而 會(huì)降低玉米的 WUE ，雜交種戶單四號(hào) 合適的根冠比、深層根系的較多分布有利于提高其 水分利用。因此過(guò)大的根系生長(zhǎng)反而對(duì)水分高效利 用有不利影響。?在小麥從 2nT6n 的進(jìn)化過(guò)程中，隨染色體倍性的增加，小麥的生物量呈遞增進(jìn)化趨勢(shì)，而

6、根系生長(zhǎng)則呈遞減進(jìn)化趨勢(shì)（根重、根長(zhǎng)、根系表面積均降低） ，根冠比也呈遞 減進(jìn)化趨勢(shì)，并因此 造成小麥整株水平 WUE 呈遞增進(jìn)化趨勢(shì)， WUE 隨小麥染色體倍性的 增加而增加。?所有二倍體材料中，以法國(guó)黑麥（染色體組型RR ）的 WUE 為最高，而以斯卑爾脫山羊草（ BB ）的 WUE 為最低。在其根冠生長(zhǎng)方面，冠層生長(zhǎng)以法國(guó)黑麥為最大，以斯卑爾脫山羊草為最??；而根系則以一粒小麥和斯卑爾脫山羊草為最大，以節(jié)節(jié)麥（ DD ） 為最小， 且四組材料根系在土壤剖面的分布存在差異， 50cm 以下， A、 B 兩染色體組小麥 的根重 明顯大于 D 、R 組小麥， A、B 兩組小麥的根冠比也明顯大于

7、D、R 組小麥?？梢?jiàn)， 不同染色體組 在控制小麥生長(zhǎng)和 WUE 方面的作用不同。6? N、P 影響了干旱下玉米葉片的氣體交換能力，表現(xiàn)為提高了干旱下玉米葉片的氣孔導(dǎo)度和光合速率， 且N的作用要大于P的作用；N具有同時(shí)降低玉米葉片光合作用的氣孔和非氣孔限制的作用，而 P 提高玉米光合則主要是由于降低了干旱下的非氣孔限制。施 用 N、P 明顯改變了干旱下 玉米的根系行為，表現(xiàn)為降低了干旱下根源ABA 濃度，也同時(shí)降低了其ZRs濃度；N、P提高了玉米根系的水力導(dǎo)度，且N的作用要明顯大于 P的作用；促進(jìn)了玉米的生長(zhǎng)， 但由于 P 對(duì)玉米根系生長(zhǎng)的較大促進(jìn)作用，使得 N 降低了玉米的根冠比，而 P 提高

8、了玉米的根冠比。由于施用N、 P 對(duì)玉米根系行為和根冠關(guān)系的影響，因而明顯提高了玉米的葉片和整株水平 WUE ，且在嚴(yán)重干旱下 P 的促進(jìn)作用更為明顯。7 ?較大的根系、較高的根源 ABA 濃度是作物適應(yīng)干旱的重要機(jī)制，但其對(duì)作物在干 旱下生存 的重要性要大于其對(duì)生產(chǎn)力和水分利用的重要性， 因此， 通過(guò)人為措施減小根系 生長(zhǎng)、 降低根源 ABA 濃度，增強(qiáng)根系功能（吸水能力）應(yīng)在提高作物 WUE 方面有重要作 用 關(guān)鍵詞 ：根冠關(guān)系，根系行為，水分利用效率，調(diào)控Regulation of Root-shoot Relations to Crop Water UsePh.D. Student:

9、Zhang SuiqiSupervisor: Prof. Shan LunWater availability is a major determinate of crop productivity in arid and semi-arid regions of the world, thus the high use efficiently of water should be center of the crop production in this regions. One solution to this problem is to irrigate in dry environme

10、nt, i.e. to modify the environment to suit the crops. Another solution is to select and cultivate crops requiring less water for growth (increase crop water use efficiency), i.e. to modify the crop to suit the environment better. Water use efficiency (WUE) may be expressed at various level. A higher

11、 WUE at equal water uptake is a desirable trait for crop because, both in rain-fed and in irrigated crops, more biomass or yield will be produced with the available water. Therefore it is not surprising that there have been extensively studied in WUE of crop, but most is focused on the crop response

12、s of shoot, root as a sensor of soil environment change, its effect on WUE is studied less. The present potted、 piped and field experiments were designed toinvestigate the effects of crop root behavior (root size 、 profile distribution 、 function 、 concentration of ABA in root xylem sap et al) and r

13、oot-shoot relations on its WUE, using wheat evolution genotype with different ploidy chromosomes sets and different corn varieties (Zea May) under various water conditions. The major results are as follows:The instantaneous water use efficiency at the leaf level ( WUEi) and the long-term water use e

14、fficiency (WUE l) at whole plant level of corn hybrid HuDan 4 is higher than that of its parent under severe drought because of relative lower ABA concentration in root xylem sap, larger root growth and root-shoot ratio, more root distribution in deeper soil layer and higher root hydraulic conductiv

15、ity(Lp) compared with its parent, which result in higher stomatal conductance (Gs) and photosynthesis rate (Pn); WUEl of HuDan 4 is higher than that of its parent under moderate and irrigated conditions, but its WUEi is lower than that of parent because of large root growth and higher root hydraulic

16、 conductivity which is advantageous to water uptake of root and transpiration loss of leaf.Stomatal behaviour of corn is controlled integratedly by both leaf water status and ABA concentration in root xylem sap under drought conditions , but it is more closely related to ABA concentration in root xy

17、lem sap than to the leaf water status. Gs of corn decrease with increase of pH in root xylem sap. Pn and transpiration rate (Tr) of corn leaf is parabolic correlated with ABA concentration in root xylem sap. WUEi is also parabola correlated with ABA concentration in xylem sap because the sensitivity

18、 of Pn and Tr to ABA concentration in root xylem sap is different. Under long term drought conditions, corn biomass, yield and WUEl are negative correlated with ABA concentration in root xylem sap, they decrease with the increase of ABA concentration in root xylem sap, and the sensitivity of yield W

19、UEl to ABA concentration in root xylem sap are larger than that of biomass WUEl, although the effect of ABA concentration in root xylem sap to biomass production is larger than that to yield. Meanwhile, root growth of corn is reduced by ABA, but its decrease is less than that of biomass. The sensiti

20、vity of different corn varieties to ABA concentration in root xylem sap is different, its order is HuDan 4 ?478?Tian 4. Therefore, it is possible to increase WUE by regulating ABA concentration in root xylem sap.Pn and Tr of corn leaf is linearity correlated with its root hydraulic conductivity (Lp)

21、, both increase with Lp increase. WUEi is parabolic correlated with root hydraulic conductivity (Lp), much or less Lp may decrease WUEi. Biomass, yield and their WUEl of corn are positive correlated with Lp, they enhance with the increase of Lp.During evoluti on process from 2n 6n, biomass and WUEI

22、of wheat in crease with the increase of chromosome ploidy sets, and root growth (root dry weight, root length and root surface area) decrease with the increase of chromosome ploidy sets, thus the ratio of root to shoot decrease with the increase of chromosome ploidy sets.Biomass and WUEl of wheat wi

23、th R chromosome set (France rye) is largest in all diploidy material, and that with B chromosome set is least in all diploidy material. Meanwhile, the root growth of wheat with A and B chromosome set is largest, and that with D chromosome set is least in all diploid material. Root profile distributi

24、on is different in all diploid material, root distribution of wheat with A and B chromosome set is greater than that with D and R chromosome set below 50 cm in soil profile, and ratio of root to shoot also is large in wheat with A and B chromosome set. Therefore, the role of various chromosome set i

25、s different in controlling growth and WUEl of wheat. Biomass and WUEl of cultivated variety with A chromosome set are greater than that of corresponding wild variety. Ratio of root to shoot of cultivated variety with A chromosome set is larger compared with corresponding wild variety. Root distribut

26、ion pattern is different between cultivate and wild variety, root distribution of wild variety with A chromosome set is larger than that of corresponding cultivated variety above 50 cm soil layer, and is reverse below 50 cm soil layer.During wheat evolution process, WUEl of wheat is negative correla

27、ted its root size, it decrease with increase of root size; and WUEl of wheat is parabolic correlated with its biomass, much or less biomass may decrease WUEl of wheat; WUEl of wheat is negative related with ratio of root to shoot. Therefore, root growth of wheat exists disadvantageous redundancy for

28、 its WUEl during evolution process, and this disadvantageous redundancy reduce with the increase of chromosome diploidy set, which result in the increase of WUEl of wheat. Biomass and yield of corn is positive correlated with its root and leaf growth, and its WUEl is parabola with root weight and bi

29、omass, much or less root and shoot growth may decrease WUEl of corn, which mean that much root growth is disadvantageous for high efficient water use of crop.Gas exchange ability of corn leaf is improved by application of N and P nutrient, but the role of N nutrient is larger than that of P nutrient

30、; Pn is increased by application of N nutrient resulted from decrease of stomatal and non-stomatal limit, but Pn is increased by P nutrient resulted from mainly decrease of non-stomatal limit. Root behaviors of corn is changed by application of N and P nutrient under drought conditions, including decrease of ABA and ZRs concentrat