【作者】 胡渊渊；

【导师】 张旺锋；

【作者基本信息】 石河子大学 ， 作物栽培学与耕作学， 2013， 博士

【摘要】 作物叶片通常被认为是主要光合器官，但许多作物的非叶绿色器官或组织，也能形成或含有叶绿素，并具有实际或潜在的光合能力，对产量形成具有一定的贡献。随着作物产量水平的提高，进一步增加单产的难度加大。重视作物非叶绿色器官的光合能力，提高作物整体光能利用效率，对作物生产水平的提高具有重要意义。本研究从棉花非叶绿色器官光合作用对产量形成的贡献、叶片和非叶绿色器官光合特性差异、水分亏缺条件下非叶绿色器官的光合生理适应性等3个方面入手，较系统的研究了棉花产量形成期各绿色器官的光合特性，揭示了非叶绿色器官光合作用对棉花产量形成的重要作用，明确了棉花不同非叶绿色器官光合作用及光保护机制，探讨了水分亏缺下棉花不同绿色器官光合作用的适应性。研究结果对进一步挖掘棉花光合物质生产潜力，提高单产奠定了理论基础，为棉花高产栽培及抗逆品种选育提供了理论依据。1．研究了棉花不同生育时期叶片、主茎秆、苞叶和铃壳的光合面积、光合放氧能力和光合关键酶活性的变化，揭示了棉花各绿色器官光合作用对产量的相对贡献率。在棉花生育后期，叶片开始衰老，非叶绿色器官的光合面积增加至整体植株的38.2%；苞叶和铃壳的光合放氧能力和光合关键酶活性的下降幅度均低于叶片。结合各器官光合面积及其光合放氧能力，估算出各绿色器官光合对植株整体产量的相对贡献率，其中棉花生育后期茎杆和果实（铃壳和苞叶）对植株整体的相对贡献率分别达12.7%和23.7%；棉铃和茎杆对铃重的相对贡献率分别为24.1%和9%。因此，棉花生育后期非叶绿色器官的光合作用对其产量形成具有重要的作用。2．研究了不同棉花品种（杂交种）非叶绿色器官的光合作用特性，阐明了杂交棉超高产形成的生理机理。研究表明，开花后5-15天，2个杂交棉新陆早43号和石杂2号叶片的光放氧能力较常规品种新陆早33号高，盛花期干物质积累速率快；随开花后天数的延长，石杂2号各绿色器官光合性能均表现出明显的下降趋势；3个不同品种（杂交种）间茎秆单位面积的光合放氧速率无显著差异，2个杂交棉生育后期茎秆具有较高的群体光合速率主要是由于株高及茎秆光合面积较高所致；与常规品种新陆早33号相比，2个杂交棉铃壳具有较高的群体光合速率，且在生育后期仍能维持较稳定的值，与杂交棉单株结铃较多、铃壳总光合面积较大有关，这是杂交棉新陆早43号和石杂2号生育后期仍能保持较高光合能力的重要原因。3．由于棉铃具有较高的呼吸速率，在苞叶和棉铃之间形成一个高浓度CO₂的微环境。本研究揭示了棉花苞叶适应高浓度CO₂微环境的生理机制。测定结果表明，光照下棉铃（苞叶和铃）的胞间CO₂浓度是500-1300μmol·mol^-1。推理认为这种高浓度CO₂微环境早在110万年前四倍体棉花出现时就存在。因此，推测认为棉花苞叶具有适应高浓度CO₂微环境的能力，并从棉花叶片、苞叶的形态和生理等方面来检验所提出的这个假说。结果表明，与叶片相比，较低气孔导度的苞叶具有较高的瞬时水分利用效率；气体交换和蛋白组分分析均表明苞叶具有较高的J_max/V_cmax比率和Rieske FeS/Rubisco比值。这些结果均与理论上提出的植物适应高浓度CO₂的机制一致，这表明苞叶可作为研究植物适应高浓度CO₂的材料。4．PSII的光失活可导致植物光化学效率下降，产量降低。植物体形成了多种保护机制来保护PSII免受光失活，然而有关非叶绿色器官光保护机制的研究较少。本文研究了棉花叶片、苞叶、主茎秆和铃壳的光保护机制，结果表明，苞叶具有较低的抗氧化酶活性，较高的ΔpH-叶黄素循环热耗散(Φ_NPQ)；主茎秆则倾向于通过依赖光和非依赖光的光化学耗散及较好的抗氧化酶体系；铃壳主要是通过其非常强的抗氧化酶体系和丰富的类胡萝卜素含量来进行热耗散，因为它具有较低的Φ_NPQ。因此，棉花各绿色器官具有不同的光保护机制。5．本研究提出了一种采用P700氧化还原动力学原理非损伤测定棉花叶片的光失活速率常数（ki）和修复速率常数（k_r）的新方法。P700氧化还原动力学面积与气相氧电极所测得的单闪脉冲的放氧量呈线型相关，表明该方法可以精确测定功能性的PSII的相对含量。采用此方法，研究了棉花叶片不同轴面接触溶液（封闭气孔效应）条件下ki和k_r的变化规律。结果表明，ki与光强有关，远轴面朝向水溶液的棉花叶片ki略高些。黑暗中两种方式放置的棉花叶片k_r相差不大。当近轴面朝向水溶液时其k_r由光强决定。当远轴面朝向水溶液时，在中度光强下k_r达到峰值，而在高光强下k_r减小。当近轴面朝向水溶液时，其k_r在弱光下先增强，此后平缓增加，高光强下k_r显著增加。高光强下，近、远轴面分别朝向水溶液叶片之间的k_r存在很大差异，这可能是由于不同程度的氧胁迫导致的修复速率常数不一致。P700氧化还原动力学测定方法能快速、无损伤地测定棉花圆叶片的功能性PSII的相对含量，对研究棉花叶片光合能力差异及其内在机制具有重要意义，为未来通过P700氧化还原动力学方法深入分析棉花非叶绿色器官的光合能力差异及其内在机制提供了重要的技术支撑。6．水分亏缺是导致作物产量降低的重要因素。研究了水分亏缺对棉花各绿色器官光合生理变化的影响机制，包括各绿色器官水分状况、光合速率、RuBPC活性及保护酶活性的变化等。水分亏缺严重降低了棉花各绿色器官的光合面积，但非叶绿色器官的下降幅度相对较小；随棉铃的发育，水分亏缺下棉花非叶绿色器官（苞叶和铃壳）的光合放氧速率、RuBPC和抗氧化酶活性的下降幅度均较叶片小，棉花非叶绿色器官的光合作用对棉株生物量积累的相对贡献率增加。更多还原

【Abstract】 Although leaf was considered as the main photosynthetic organ, many parts of crop suchas non-foliar organs which contain chlorophyll can also performance photosynthesis,contributing to carbon acquisition and yield. This research was conducted from threeperspectives:1) changes in photosynthetic capacity of non-foliar organs in cotton and relativecontribution to yield during growth stages;2) differences in photosynthesis charactertics ofnon-foliar organs in cotton and3) the photosynthetic adaptations of green organs in cottonrespond to water stress. On the basis of the three points above, photosynthetic charactertics,relative contribution to its yield and adaptation respond to water stress of non-foliar organs incotton were studied to elucidate a) the changes in photosynthetic rate of green organs incotton during growth stages and the important photosynthetic contribution of non-foliar organto yield formation especially at later growth stage, b) differences in photosynthesischaractertic and photoprotection mechanism of non-foliar organ, and c) effects of waterdeficit on physiological process and the relative contribution of each organ to yield in cottonwas explored. This research may help to increase the potential of photosynthate production,thereby improving cotton yield. Additionally, the results obtained can provide theoreticalbasis for high-yielding cotton production and drought-tolerant cotton breeding. Below are themain results in this thesis:1. The relative photosynthetic contribution of leaves, main stem, bracts and capsule wallsin cotton was revealed by measuring their time-course of surface area development, O2evolution capacity and photosynthetic enzyme activity. Because of the early senescence ofleaves, non-foliar organs increased their surface area up to38.2%of total at late growth stage.Bracts and capsule wall showed less ontogenetic decrease in O2evolution capacity per areaand photosynthetic enzyme activity than leaves at the late growth stage. The total capacity forO2evolution of stalks and bolls （bracts plus capsule wall） was12.7%and23.7%, respectively,as estimated by multiplying their surface area by their O2evolution capacity per area. We alsokept the bolls （from15days after anthesis） or main stem （at the early full bolling stage） indarkness for comparison with non-darkened controls. Darkening the bolls and main stemreduced the boll weight by24.1%and9%, respectively. Thus, we conclude that non-foliarorgans significantly contribute to the yield at the late growth stage.2. The photosynthetic charactertics of non-foliar organs in super-high-yielding cottonduring growth stages were explored. Compared with traditional cotton Xinluzao33, thephotosynthetic rate of the main leaf of hybrid cotton Xinluzao43and Shiza2was higherduring5-15days after anthesis, which reason for faster dry matter accumulation rate ofXinluzao43and Shiza2cotton during early growth stage （Full Flowering）. However, more decrease in photosynthetic rate of green organs of Shiza2during the growth stages, whichcaused its early senescence. There was no significance in photosynthetic rate of main stemamong these three cultivars. Thus, we suggested that the high height and larger surface area ofhybrid cotton result in their better canopy photosynthetic rate of stalks at later growth stage.The photosynthetic rate of capsule wall in hybrid cotton Xinluzao43and Shiza2was higherthan that in traditional cotton Xinluzao33, and maintain stable photosynthetic rate during latergrowth stage, company with their larger surface area which all contribution their highercanopy photosynthetic rate of fruits at later growth stage.3. The rapid respiration rate of cotton （Gossypium hirsutum L.） fruits （bolls） produces aconcentrated CO₂micro-environment around the bolls and bracts. Elucidation of themechanisms by which plants adapt to elevated CO₂is needed. However, most studies of themechanisms investigated the response of plants adapted to current atmospheric CO₂. Weobserved that the intercellular CO₂concentration of a whole fruit （bract and boll） ranged from500to1300μmol mol1depending on the irradiance, even in ambient air. Arguably, this CO₂micro-environment has existed for at least1.1million years since the appearance of tetraploidcotton. Therefore, we hypothesized that the mechanisms by which cotton bracts have adaptedto elevated CO₂will indicate how plants will adapt to future increased atmospheric CO₂concentration. To test the hypothesis, the morphological and physiological traits of bracts andleaves of cotton were measured, including stomatal density, gas-exchange and proteincontents. Compared with leaves, bracts showed significantly smaller stomatal conductancewhich resulted in a significantly higher water use efficiency. Both gas-exchange and proteincontent showed a significantly greater RuBP regeneration/RuBP carboxylation capacity ratio(J_max/V_cmax) in bracts than in leaves. These results agree with the theoretical prediction thatadaptation of photosynthesis to elevated CO₂requires increased RuBP regeneration. Cottonbracts are readily-available material for studying adaption to elevated CO₂.4. Photoinactivation of Photosystem II （PS II） during photosynthesis can lead to the lossof photochemical efficiency and decrease in crop yield. Plants have evolved variousphotoprotective strategies to ameliorate photoinactivation of PS II. Non-leaf organs of cottonalso contribute to carbon gain, but it is not clear how they photoprotect themselves. This studyinvestigated the photoprotective mechanisms in the leaf, bract, main stem and capsule wall ofcotton. Our results suggested that the bract mainly relies on high activities of antioxidativeenzymes and high ΔpH-and xanthophyll-regulated thermal dissipation (Φ_NPQ) forphotoprotection. The main stem preferentially dissipated its absorbed light energy vialight-regulated as well as light-independent non-photochemical quenching, aided by themoderately high activities of antioxidative enzymes. The capsule wall was less able to removereactive oxygen species due to lower activities of antioxidative enzymes, and less able todissipate energy via heat due to its lower Φ_NPQ. Its main photoprotective mechanisms seem tobe （a） direct quenching of the energy by abundant carotenoids and （b） light-independentconstitutive thermal dissipation via Φf,D. The green organs of cotton have different ways touse or dissipate energy. 5. Here we report on a whole-tissue determination of the rate coefficient ofphotoinactivation ki, and that of repair k_rin cotton leaf discs. The P700kinetics area, directlyproportional to the oxygen yield per single-turnover, saturating flash, was used to obtain bothkiand k_r. Changes in kiand k_rof two orientations （abaxial/adaxial surface contacting water）were investigated in this study. The value of ki, directly proportional to irradiance, wasslightly higher when CO₂diffusion into the abaxial surface （richer in stomata） was blocked bycontact with water. The value of k_r, sizable in darkness, changed in the light depending onwhich surface was blocked by contact with water. When the abaxial surface was blocked, k_rfirst peaked at moderate irradiance and then decreased at high irradiance. When the adaxialsurface was blocked, k_rfirst increased at low irradiance, then plateaued, before increasingmarkedly at high irradiance. At the highest irradiance, k_rdiffered by an order of magnitudebetween the two orientations, attributable to different extents of oxidative stress affectingrepair. The P700kinetics area is a rapid, whole-tissue and in vivo measurement of relativeassay of functional PSII content, can help to explore the differences and underlyingmechanisms in photosynthetic capacity of leaf in cotton and also provide technical basis forexploring the differences and underlying mechanisms in photosynthetic capacity of variousgreen organs in cotton.6. Water deficit is one of the most important causes of decreased yield in cultivatedplants. The physiological response of each organ to water deficit has not beencomprehensively studied in relation to the water status, photosynthetic rate, photosyntheticenzyme activity, antioxidant enzymes. Water deficit significantly decreased the surface area ofeach organ, but to a lesser extent in non-foliar organs. Non-foliar organs （bracts and capsulewall） showed less ontogenetic decrease in O2evolution capacity and in RuBPC activity （perdry weight） as well as better antioxidant systems than leaves at various days after anthesis. Addition ally, the relative contribution of biomass accumulation of non-foliar organs to thewhole cotton plant was estimated from the surface area, photosynthetic duration and the O2evolution capacity per area. Our result s showed that the relative contribution of biomassaccumulation of non-foliar organs increased under water deficit.更多还原