【作者】 杨天仪；

【导师】 黄丹枫； 王世平；

【作者基本信息】 上海交通大学 ， 生物化学与分子生物学， 2007， 博士

【摘要】 根域限制在抑制果树营养生长、提高果实品质等方面的效果几乎被所有研究所肯定,根域限制条件下果树树体的氮素营养和碳素营养状况发生了显著的变化。但这些变化究竟发生在氮素与碳素代谢的哪些环节尚不是很清楚,而这一问题正是理解根域限制的作用机制,了解果树氮素吸收、氮素与碳素同化和运转规律的“瓶颈”问题。为此,本研究以葡萄树氮素和碳素两大营养代谢作为切入点,探索了根域限制条件下葡萄树体氮素和碳素营养所发生的变化,以及这些变化与根域限制控长、提高果实品质之间的关系,得出以下结果:1.根域限制条件下“藤稔”葡萄树体的生长、结果与营养状况分析表明:根域限制葡萄树新梢生长受到明显抑制,从幼果膨大期开始新梢长度显著低于对照;叶片面积也表现出相同的趋势;叶片光合速率日变化也始终低于对照,其中在8:00、10:00和12:00出现了显著或极显著差异;根域限制显著提高了果皮花青素和果实中可溶性固形物含量,降低了果实中酸的含量,从而提高了果实的品质;尽管不同器官、组织在不同发育阶段存在差异,但新叶、成熟叶、新根和褐根等器官中的全N、NO3-、NH4+、P、K+、Mg2+等矿质元素含量低于对照。2.根域限制条件下“峰后”葡萄根系的NO3-吸收动力学研究表明:根域限制提高了NO3-的吸收速率,降低了葡萄根系NO3-高亲和转运子(HATS)的Km值,增大了HATS的Vmax值,即增强了HATS对NO3-的亲和力和HATS与LATS的NO3-吸收速率,但是由于它显著地降低了根系的鲜重,所以导致了根系对NO3-净吸收量的显著降低。3.根域限制下“藤稔”葡萄树氮素代谢相关酶活性日变化研究表明:叶片与根系中硝酸还原酶(NR)、亚硝酸还原酶(NiR)与谷酰氨合成酶(GS)活性的日变化在6:00最低,10:00达到最高值,此后开始下降,18:00有小幅回升。成熟叶片中NR的活性整天都低于对照,从10:00到18:00褐根中NR活性低于对照,在12:00以后根域限制树白根中NR的活性也低于对照;在10:00根域限制的新叶、成熟叶、褐根、白根的NiR活性都低于对照,14:00成熟叶、褐根NiR活性变小但仍低于对照,18:00新叶中的NiR活性又低于对照,且存在显著差异;从6:00到14:00新叶中GS活性显著低于对照,在成熟叶中根域限制处理和对照的GS活性没有出现显著性差异,在14:00褐根中GS活性,在18:00白根中GS活性均低于对照。可见,根域限制不同程度地降低了NO3-同化的关键酶的活性,从而降低了NO3-的同化。4.采用“浆果杯”技术,研究了根域限制条件下“峰后”葡萄果实的韧皮部24h糖卸载,发现其变化大体上呈现“三峰型”曲线,峰值分别出现在9:00、17:00和21:00前后,上午峰值分别为下午和晚上的1.7和1.2倍左右。两个谷值则分别出现在15:00和3:00左右,下午谷值约为凌晨的1.5倍左右;糖卸载量白天(6:00-19:00)约为晚上(20:00-5:00)的1.7-2.0倍,上午(6:00-11:00)为下午(12:00-16:00)的1.7-3.1倍,前半夜(17:00-23:00)为后半夜(0:00-5:00)的2.5倍;单位果实鲜重的糖卸载量根域限制处理始终高于对照,约为对照的1.5倍。可见,根域限制促进了葡萄果实的韧皮部糖卸载。5.外源脱落酸(ABA)处理明显促进了“峰后”葡萄果实韧皮部的糖卸载,外源玉米素(ZT)处理对糖卸载的效果则取决于内源ABA的浓度及ABA与细胞分裂素(CTK)二者的平衡;糖运输的能量或载体抑制剂曙红B(EB)与乙二醇双乙胺醚-N ,N ,N′,N′-乙酸(EGTA)处理表明了根域限制处理“峰后”葡萄近成熟果实韧皮部糖卸载的途径未发生改变,与对照一样属于质外体卸载途径,是需要载体和能量的。综上所述,根域限制处理降低了葡萄树对NO3-等矿质元素的吸收与同化,导致了树体内氮素等矿质营养水平的降低,是树体营养生长受到抑制的主要原因;尽管EB与EGTA处理表明了根域限制近成熟葡萄果实韧皮部糖卸载的途径未发生改变,但通过外源ABA与ZT处理发现,根域限制显著促进葡萄果实韧皮部的糖卸载是由于内源于根系的CTK和ABA的浓度发生变化所致,是根域限制葡萄果实糖分积累增加、果实品质提高的重要或主要原因。本研究的这些发现,为果树根域限制栽培奠定了理论基础。更多还原

【Abstract】 Many experiments in fruit trees revealed that root restriction inhibited vegetative growth and improved fruit quality, which suggested that nitrogen and carbon metabolisms might be changed. However, up to date, it is still unknown the key steps exactly where the alterations of nitrogen and carbon metabolism took place, and these are bottle-necked problems for well understanding the root restriction mechanism and the rules of nitrogen absorption, as well as the nitrogen and carbon assimilation and translocation. Therefore, the present study, with nitrogen nutrition as a cut-in point, aimed at the sugar accumulation in fruit, probed into the changes of nitrogen and carbon metabolisms in grapevines under root restriction and their relations with vegetative growth and fruit quality. The results showed as follows: 1. The analysis of vegetative growth, fruit quality and the grapevine nutrition of“Fujiminori”under root restriction showed that the shoot growth was inhibited and the shoot length was significantly shorter than that of control after little berry enlargement stage; the leaf area also showed the same trend as the shoot length; leaf photosynthetic rate was lower than that of control all the while and reached significant level at 8:00, 10:00 and 12:00; root restriction significantly increased the anthocyanin content in skins and total soluble solids in fruits, and decreased the acid content in fruits, thereby improved fruit quality; the concentrations of total N in new leaves and brown roots, NO3- in all leaves and roots, NH4+ and P in new leaves, K+ in new leaves and mature leaves and Mg2+ in mature leaves were lower than those of control, and the concentration of Ca2+ had no significant difference compared with control.2. Nitrate uptake kinetics of“Fenghou”grapevine under root restriction indicated that root restriction enhanced the nitrate uptake rate, decreased the Km value and increased Vmax value, that is to say, root restriction depressed the affinity of nitrate high-affinity transport system (HATS) and improved the nitrate uptake rates of both high (HATS) and low-affinity transport system (LATS). However, the amount of net nitrate uptake decreased significantly because of the reduction of root fresh weight under root restriction. 3. The daily variation of enzyme activities related to nitrogen metabolism in“Fujiminori”grapevine under root restriction showed that NR, NiR and NR activity displayed similar trend, the minimum appeared at 6:00 and reached the maximum at 10:00, then declined and with a little rise at 18:00; NR activity in mature leaves all the daytime, in brown roots from 10:00 to 18:00, in white roots after 10:00 were lower than those of control; NiR activity in new leaves, mature leaves, brown roots and white roots at 10:00, in mature leaves and brown roots at 14:00, in new leaves at 18:00 were also lower than control; and GS activity in new leaves from 6:00 to 14:00, in brown roots at 14:00, in white roots at 18:00 were lower compared with control. So, root restriction reduced the key enzyme activities related to nitrate metabolism, thereby decreased nitrate assimilation.4. By using“berry-cup”technique, the 24h variations of sugar phloem unloading in ripening grape berries were determined. Their variations exhibited three peaks and two bottoms. The peaks appeared at 9:00, 17:00 and 21:00, the peak value in the morning was about 1.7 and 1.2 fold higher than those in the afternoon and evening, respectively. The two bottoms appeared at 3:00 and 15:00, the bottom value in the afternoon was about 1.5 fold higher than that in the early morning. Moreover, the amount of sugar phloem unloading at daytime (6:00-19:00) was 1.7 (control)-2.0 (RR) fold higher than that at night (20:00-5:00), and that in the morning (6:00-11:00) were 1.7 (control)-3.1 (RR) fold, and before midnight (17:00-23:00) were 2.5 fold higher than that in the afternoon (12:00-16:00) and after midnight (0:00-5:00), respectively. Compared with the control, the amount of sugar phloem unloading per fresh weight of root-restricted berries was higher all the time (about 1.5 fold), therefore root restriction enhanced sugar phloem unloading of grape berries.5. Sugar phloem unloading of“Fenghou”grape berries was accelerated by external abscisic acid (ABA) application. However, the effect of external zeatin (ZT) treatment on sugar phloem unloading was determined by the concentrations of endogenous ABA and cytokinin (CTK) and their balance in grapevine. Treated with erythrosin B (EB) and ethyleneglycol-bis (β-aminoethyl ether)-N, N, N′, N′-tetraacetic acid (EGTA), the inhibitors of energy or transporters needed by sugar transport, the variations of sugar phloem unloading indicated that the pathway of sugar phloem unloading of ripening“Fenghou”grape berries did not changed and was the same as control, which belongs to apoplastic pathway and needs transporters and energy.From all above, root restriction decreased the uptake and assimilation of mineral elements such as NO3- etc and lowered mineral element content in grapevines, which it is maybe the main cause resulting in the inhibitory vegetative growth of grapevines. In addition, although the sugar phloem unloading pathway of root restricted grape ripening berries did not change (confirmed by EB and EGTA treatment experiments), however, it is the concentration alterations of endogenous ABA and CTK under root restriction that led to sugar phloem unloading being enhanced (confirmed by external ABA and ZT application experiments), which was the very important or main reason why root restriction could improve fruit quality significantly. The findings of the present study may provide a theoretical base for root restriction of fruit trees.更多还原