Combined effect of shading time and nitrogen level on grain filling and grain quality in japonica super rice

There is limited information about the combined effect of shading time and nitrogen(N) on grain filling and quality of rice. Therefore, two japonica super rice cultivars, Nanjing 44 and Ningjing 3, were used to study the effect of shading time and N level on the characteristics of rice panicle and grain filling as well as the corresponding yield and quality. At a low N level(150 kg N ha~(–1), 150 N), grain yield decreased(by 21.07–26.07%) under the treatment of 20 days of shading before heading(BH) compared with the no shading(NS) treatment. These decreases occurred because of shortened panicle length, decreased number of primary and secondary branches, as well as the grain number and weight per panicle. At 150 N, in the treatment of 20 days of shading after heading(AH), grain yield also decreased(by 9.46–10.60%) due to the lower grain weight per panicle. The interaction of shading and N level had a significant effect on the number of primary and secondary branches. A high level of N(300 kg N ha~(–1), 300 N) could offset the negative effect of shading on the number of secondary branches and grain weight per panicle, and consequently increased the grain yield in both shading treatments. In superior grains, compared with 150 N NS, the time to reach 99% of the grain weight(T_(99)) was shortened by 1.6 to 1.7 days, and the grain weight was decreased by 4.18–5.91% in 150 N BH. In 150 N AH, the grain weight was 13.39–13.92% lower than that in 150 N NS due to the slow mean and the maximum grain-filling rate(GR_(mean )and GR_(max)). In inferior grains, grain weight and GR_(mean) had a tendency of 150 N NS150 N BH150 N AH. Under shaded conditions, 300 N decreased the grain weight due to lower GR_(mean) both in superior and inferior grains. Compared with 150 N NS, the milling and appearance qualities as well as eating and cooking quality were all decreased in 150 N BH and 150 N AH. Shading with the high level of 300 N improved the milling quality and decreased the number of chalky rice kernels, but the eating and cooking quality was reduced with increased chalky area and overall chalkiness. Therefore, in the case of short term shading, appropriate N fertilizer could be used to improve the yield and milling quality of rice, but limited application of N fertilizer is recommended to achieve good eating and cooking quality of rice.     

谷子对拔节期弱光胁迫的光合生理响应

为阐述拔节期弱光胁迫降低谷子产量的光合生理机制,以张杂谷5号和晋谷21号为研究对象,在拔节期分别进行30%、60%和85%的遮阴处理15 d,以不遮阴作为对照,探究谷子叶片的光合色素含量、光合特性、叶绿素荧光参数及产量对其的响应规律。结果表明,遮阴处理降低了2个品种谷子叶片的光合色素含量、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、表观光合电子传递速率(ETR)、PSⅡ实际光化学量子产量(ΦPSⅡ)、光化学猝灭系数(q P)、非调节性能量耗散量子产量[Y(NO)]、穗长、穗重、穗粒重和产量,却显著提高了胞间CO2浓度(Ci)和调节性能量耗散量子产量[Y(NPQ)]。张杂谷5号的表观光合电子传递速率(ETR)、PSⅡ实际光化学量子产量(ΦPSⅡ)和产量在遮阴30%时显著下降,而晋谷21号在遮阴程度超过60%时才显著变化。总之,拔节期弱光胁迫下,谷子叶片的光合色素含量降低,捕捉利用光能的能力减弱,PSⅡ光化学活性降低,光合作用变弱,最终影响产量;张杂谷5号比晋谷21号对弱光胁迫更为敏感。本研究结果为拔节期通过改善谷子叶片的光合功能来增强抗弱光胁迫以达到稳产指明了方向,并为选育耐弱光胁迫谷子提供了依据。     

遮阴处理对红龙草生长的影响

试验对红龙草在1层和2层遮阴处理下的生长状况进行了对比试验,结果表明:(1)红龙草为喜阴草本,在遮阴条件下生长良好。且1层遮阴处理下其植株的密度和高度增加幅度最大;(2)遮阴影响红龙草叶片颜色的改变。遮阴越强,红色叶片数量越多;遮阴越小,红色叶片数量越少,而绿叶数增多。红色叶片多集中生长于植株的上半部;(3)1层遮阴处理的红龙草其叶片数量增长幅度明显大于自然光照下或2层遮阴处理的红龙草植株。     

草本植物遮荫效应的研究进展

从遮荫对草本植物的生长环境、生理生化特性、形态解剖结构、营养分配及产量影响方面进行了综述.遮荫可明显改变草本植物的生长环境,进而对其生理生化特性及产量产生较大的影响.草本植物为适应荫蔽的环境,导致在光合作用单位、电子传递、光合色素含量、内源激素及酶活性、植株形态解剖结构、营养物质的吸收及分配等方面产生变化,以保证在遮荫下仍能充分利用光能,维持生长所需的能量平衡,进行正常的生命活动.     

遮阴对三种豆科牧草光合特性和叶绿素荧光参数的影响

为了探讨豆科牧草在遮阴条件下生态适应性及寻求适度的遮阴比例,系统研究了不同程度的遮阴处理(0%,48%,70%,95%)对3种豆科牧草的光合特性和叶绿素荧光参数的影响。结果表明,随着遮阴强度的提高,白三叶的光补偿点和光饱和点减小,紫花苜蓿与草木樨在适度遮阴条件下可维持较低的光补偿点和光饱和点;3种豆科牧草叶片叶绿素a、叶绿素b和叶绿素a+b的含量逐渐降低,且相同遮阴处理下白三叶均高于其他2种豆科牧草,紫花苜蓿在Y3处理条件下表现为叶绿素a/b值最大;3种豆科牧草PSⅡ受到损伤的程度为紫花苜蓿＞草木樨＞白三叶;遮阴会使白三叶与草木樨的ΦPSⅡ和qP略有降低,但在Y3处理条件下,白三叶的ΦPSⅡ和qP会略有增加,而紫花苜蓿随着遮阴强度的提高,其ΦPSⅡ和qP呈先增加后减小的趋势。3种豆科牧草的耐阴强度顺序为:白三叶＞草木樨＞紫花苜蓿,其中,白三叶在70％以上的遮阴强度下仍然可以长势良好,而草木樨在48％的遮阴强度下有利于生长,紫花苜蓿则受遮阴影响较大。     

遮光对茶秆竹笋外观形态及不同部位间营养成分含量的影响

目的 探究不同光照强度对茶秆竹笋的外观形态和各部位间营养成分含量的影响,为茶秆竹笋品质调控和科学培育提供指导。 方法 用套袋的方式对竹笋遮光,设置CK（自然光照）、L1（50%自然光照）和L2（完全遮光）3种光照处理,采样后测定分析竹笋外观形态指标和各部位间营养成分含量的变化。 结果 遮光后茶秆竹笋的基径、长度和笋个体质量下降,中度遮光下可食率降低,完全遮光后可食率升高;笋箨与笋肉的L*值、a*值和b*值均上升,笋箨叶绿素含量减少,花青素含量增加,色素含量与色泽指标间存在显著相关性。随着光照强度减弱,笋尖部的蛋白质和脂肪含量增加,笋中部的氨基酸总量与必需氨基酸比例先升高后降低,笋基部的甜味、苦味和芳香类氨基酸比例先下降后上升,各部位的灰分含量先增多后减少,可溶性糖含量先降低后升高,维生素C、纤维素和酚类物质的含量减少。 结论 遮光后茶秆竹笋的外观品质更佳,苦味物质含量减少,口感明显提升,不同光照强度下各部位营养成分含量的变化存在差异。     

Effects of shading stress during the reproductive stages on photosynthetic physiology and yield characteristics of peanut(Arachis hypogaea Linn.)

In intercropping systems,high-positioned crops often exert shading stress on low-positioned crops,thus affecting the agronomic characteristics of the low-positioned crops.This study determined the mechanisms of photosynthetic,physiological and yield variations among peanut cultivars under shading stress.Four peanut cultivars,S60,C4,P12,and YS151,were grown in the field and subjected to shading stress for 77 days during reproductive stages.S60 and P12 showed lower yield and reduced biomass accumulation than C4 and YS151 under shading stress.Shading stress induced higher antioxidant enzyme activities in S60 and P12,relative to C4 and YS151.Under shading stress,S60 and P12 showed a higher lighttrapping capability than C4 and YS151,which was associated with changes in chlorophyll (Chl) a and b contents,and Chl a/b ratio.The net photosynthetic rate,stomatal conductance and transpiration rates of C4 and YS151 were decreased,but the intercellular CO_2 concentration increased under shading stress.The results demonstrated that non-stomatal limiting factors decreased the photosynthetic capacity of peanut under shading stress.The maximum photochemical efficiency of PSII(F_v/F_m) and non-photochemical quenching (NPQ) were higher in S60 and P12 than in C4 and YS151 under shading stress.These results suggest that S60 and P12 could absorb more light energy from weak light environments for photosynthesis than C4 and YS151 and dissipate the excess energy in the form of heat to improve their light protection ability.This study explains the inter-variety differences in shading stress tolerance in peanut and provides physiological parameters for guiding the selection of shade-tolerant cultivars.     

遮阴对印度紫檀苗木成活率的影响

采用90％、75％和50％不同透光度的阴网进行遮阴培育印度紫檀苗木,以不遮阴为对照,在小苗移植后45,90,210d调查苗木成活率,结果表明：印度紫檀幼苗期生长不需要全日照,用遮阴网遮阴其成活率可提高40．6～44．2个百分点。用透光度为75％或50％的阴网遮阴较适宜幼苗生长。     

Effect of green infrastructures supported by adaptative solar shading systems on livability in open spaces

Lack of thermal comfort in the existing building stock in many warm summer climates and the COVID-19 pandemic have increased residents' temporary occupation of urban open spaces. However, climate change and other effects such as urban heat islands are also negatively affecting the livability of these spaces. Therefore, strategies are needed to improve the thermal conditions in these areas. In this context, the research designs, simulates and assesses an urban green infrastructure supported by an adaptative solar shading system. For this purpose, a public square to be renovated in Seville (Spain) is chosen. After an analysis of the current situation, more vegetation is added. However, trees are not planted fully grown, so their cover is not enough in the short term and an artificial system that protects from the sun by casting shade and that adapts to both their growth and the seasons is included. The urban space is characterized by on-site measurements, proposing four (initial, intermediates and final) scenarios using computational fluid dynamics simulations in an holistic microclimate modelling system. In turn, changes in thermal comfort are analyzed using the COMFA model. Results show that the air and surface temperature are decreased, reducing the number of hours in discomfort by 21% thanks to incorporating the green structure and by 30% due to the vegetation. It can be concluded that the use of these temporary urban prostheses enables urban spaces regenerated with vegetation to be enjoyed without waiting 20 or 30 years for the trees to mature, encouraging people to spend more time outdoors from the start of the intervention.     

Decreased panicle N application alleviates the negative effects of shading on rice grain yield and grain quality

Light deficiency is a growing abiotic stress in rice production. However, few studies focus on shading effects on grain yield and quality of rice in East China. It is also essential to investigate proper nitrogen (N) application strategies that can effectively alleviate the negative impacts of light deficiency on grain yield and quality in rice. A two-year field experiment was conducted to explore the effects of shading (non-shading and shading from heading to maturity) and panicle N application (N_DP, decreased panicle N rate; N_MP, medium panicle N rate; N_IP, increased panicle N rate) treatments on rice yield- and quality-related characteristics. Compared with non-shading, shading resulted in a 9.5–14.8% yield loss (P<0.05), mainly due to lower filled-grain percentage and grain weight. N_MP and N_IP had higher (P<0.05) grain yield than N_DP under non-shading, and no significant difference was observed in rice grain yield among N_DP, N_MP, and N_IP under shading. Compared with N_MP and N_IP, N_DP achieved less yield loss under shading because of the increased filled-grain percentage and grain weight. Shading reduced leaf photosynthetic rate after heading, as well as shoot biomass weight at maturity, shoot biomass accumulation from heading to maturity, and nonstructural carbohydrate (NSC) content in the stem at maturity (P<0.05). The harvest index and NSC remobilization reserve of N_DP were increased under shading. Shading decreased (P<0.05) percentages of brown rice, milled rice, head rice, and amylose content while increasing (P<0.05) chalky rice percentage, chalky area, chalky degree, and grain protein. N_MP demonstrated a better milling quality under non-shading, while N_DP demonstrated under shading. N_DP exhibited both lower chalky rice percentage, chalky area, and chalky degree under non-shading and shading, compared with N_MP and N_IP. N_DP under shading decreased amylose content and breakdown but increased grain protein content and setback, contributing to similar overall palatability to non-shading. Our results suggested severe grain yield and quality penalty of rice when subjected to shading after heading. N_DP improved NSC remobilization, harvest index, and sink-filling efficiency and alleviated yield loss under shading. Besides, N_DP would maintain rice’s milling, appearance, and cooking and eating qualities under shading. Proper N management with a decreased panicle N rate could be adopted to mitigate the negative effects of shading on rice grain yield and quality.