中国野生种毛葡萄光合特性的研究

毛葡萄（ＶｉｔｉｓｑｕｉｎｑｕａｎｇｕｌａｒｉｓＲｅｈｄ）的净光合速率日变化值明显高于山葡萄、宝石、白玉霓，且无栽培品种光合作用的“午休”现象。毛葡萄的净光合速率与其它野生种葡萄和栽培品种比较也表现出较高水平。在进行ＣＯ２饱和点和补偿点测定时，毛葡萄也较栽培品种白玉霓有较强的光合作用，因此，毛葡萄是葡萄高光合效率育种的优良野生种质资源。     

农作物抗旱性鉴定仪的研制和应用

依据陈毓荃等首次提出的连续升温电导法，研制了ＮＫＪ－１型农作物抗旱性鉴定仪，对１４种小麦抗旱性的鉴定结果与田间观测结果一致，也适于果树抗热性鉴定。     

包心菜无菌苗子叶及叶片原生质体高频分裂和高频植株再生

以包心菜子叶和叶片原生质体为材料。经不同液体培养基(Bp1,Bp2,B1)浅层培养,再生细胞高频分裂并形成愈伤组织。愈伤组织经扩增后转移到分化培养基上诱导植株分化,从这两种原生质体中获得了再生植株。在原生质体培养过程中,原生质体及细胞团的褐化程度与培养基中的有机成分的多少有关。原生质体的分化频率与培养基中植物激素种类关系甚大。在植株分化时,谷氨酰胺和腺嘌呤对植株分化有很大促进作用。另外,原生质体的来源及原生质体培养基对原生质体植株分化能力均有不同的影响。     

桃果实蒸腾强度对源叶净光合效率及相关生理反应的影响

在果核硬化期和果实最后迅速生长期,对艳丰一号桃果实浸涂10倍和100倍的液体石蜡溶液,与果实未浸涂液体石蜡的对照相比,果实蒸腾强度分别降低了57.9%和41.4%,且源叶净光合效率(Pn)和气孔导度(Gs)降低而叶表面温度(Tl)升高,并在果实迅速生长期间,果实浸涂液体石蜡处理和对照之间存在显著性差异。进一步研究表明,无论是在果核硬化期还是在果实最后迅速生长期,当Gs小于0.2mol/m2·s时,Pn和Gs呈极显著直线正相关关系,且果实浸涂液体石蜡处理的源叶的Tl随Gs减小急剧升高。源叶Pn对Tl的响应均呈极显著抛物线相关关系,但同一Tl条件下,果实浸涂液体石蜡处理的Pn低于对照。因此认为,果实蒸腾强度可能通过作用叶片的Gs调节Tl进而对源叶的Pn进行调控,气孔开张度减小、Tl升高,可能是果实蒸腾强度减弱时调控Pn重要机制之一。     

Physiological processes associated with salinity tolerance in an alfalfa half‐sib family

We previously reported an alfalfa half‐sib family, HS‐B, with improved salt tolerance, compared to parental plants, P‐B. In this study, we conducted additional experiments to address potential physiological mechanisms that may contribute to salt tolerance in HS‐B. Vegetatively propagated HS‐B and P‐B plants were treated with a nutrient solution (control) or a nutrient solution containing NaCl (EC = 12 dS/m). Shoots and roots were harvested at various time points after treatment for quantification of proline, soluble sugar, and H₂O₂ using spectrophotometers. Subcellular localization and quantification of Na in roots were conducted using a Na⁺‐specific dye under a confocal microscope. HS‐B produced 86 and 89% greater shoot and root dry biomass, respectively, compared to parental plants, P‐B, under salinity in the greenhouse. Under saline conditions the HS‐B shoots accumulated 115% and roots 55% more soluble sugars than P‐B counterparts. The non‐saline HS‐B shoots, however, showed 72% less soluble sugars than the non‐saline P‐B plants. Under saline conditions HS‐B accumulated 39% less proline in shoots, while roots accumulated 56% more proline, compared to their P‐B parents. HS‐B plants also showed a greater reduction of stomatal conductance under mild saline stress. HS‐B shoots and roots contained 3–4 times less reactive oxygen species (H₂O₂) after salt treatment compared to P‐B plants. Sodium localization and distribution analysis using Na⁺‐specific dye revealed HS‐B plants accumulated 88% and 48% less Na⁺ in stele and xylem vessels compared to P‐B. The study provides insights into the potential mechanisms that may contribute to salt tolerance in HS‐B: maintaining RWC by accumulating soluble sugars while reducing transpiration, maintaining healthy status by reducing oxidative stresses, and preventing salt toxicity by reducing accumulation of Na⁺ inside root cells and xylem.     

Genotypic Variation for Tolerance to Transient Drought During the Reproductive Phase of Brassica rapa

Brassica rapa L. is a genetically diverse parent species of the allotetraploid species, oilseed rape (B. napus) and a potential source of drought tolerance for B. napus. We examined the effect of a 13‐day drought stress period during the early reproductive phase, relative to a well‐watered (WW) control, on subsequent growth and development in nine accessions of B. rapa and one accession of Brassica juncea selected for their wide morphological and genetic diversity. We measured leaf water potential, stomatal conductance, water use, and leaf and bud temperatures during the stress period and aboveground dry weight of total biomass at maturity. Dry weight of seeds and reproductive tissue were not useful measures of drought tolerance due to self‐incompatibility in B. rapa. The relative total biomass (used as the measure of drought tolerance in this study) of the 10 accessions exposed to drought stress ranged from 47 % to 117 % of the WW treatment and was negatively correlated with leaf‐to‐air and bud‐to‐air temperature difference when averaged across the 13‐day stress period. Two wild‐type (B. rapa ssp. sylvestris) accessions had higher relative total and non‐reproductive biomass at maturity and cooler leaves and buds than other types. We conclude that considerable genotypic variation for drought tolerance exists in B. rapa and cooler leaves and buds during a transient drought stress in the early reproductive phase may be a useful screening tool for drought tolerance.     

Physiological Response of Multiple Contrasting Rice (Oryza sativa L.) Cultivars to Suboptimal Temperatures

The physiological response of multiple rice cultivars, eighteen initially and eight cultivars later on, to suboptimal temperatures (ST) conditions was investigated in laboratory and outdoor experimental conditions. Treatment with ST decreased growth in different extents according to the cultivar and affected the PSII performance, determined by chlorophyll fluorescence fast‐transient test, and stomatal conductance, regardless the experimental condition. Two groups of cultivars could be distinguished on the base of their growth and physiological parameters. The group of cultivars presenting higher growths displayed optimal JIP values, and higher instantaneous water use efficiency (WUE_i), due to a lower Gs under ST, unlike cultivars showing lower growth values, which presented worse JIP values and could not adjust their Gs and hence their WUE_i. In this work, we detected at least two cultivars with superior tolerance to ST than the cold tolerant referent Koshihikari. These cultivars could be used as parents or tolerance donors in breeding for new crop varieties. On other hand, positive and significant correlations between data obtained from laboratory and outdoor experiments suggest that laboratory measurements of most of the above mentioned parameters would be useful to predict the response of rice cultivars to ST outdoor.     

Effects of CO2 Enrichment and Drought on Photosynthesis,Growth and Yield of an Old and a Modern Barley Cultivar

Susceptibility of crops to drought may change under atmospheric CO₂ enrichment. We tested the effects of CO₂ enrichment and drought on the older malting barley cultivar Golden Promise (GP) and the recent variety Bambina (BA). Hypothesizing that CO₂ enrichment mitigates the adverse effects of drought and that GP shows a stronger response to CO₂ enrichment than BA, plants of both cultivars were grown in climate chambers. Optimal and reduced watering levels and two CO₂ concentrations (380 and 550 ppm) were used to investigate photosynthetic parameters, growth and yield. In contrast to expectations, CO₂ increased total plant biomass by 34 % in the modern cultivar while the growth stimulation was not significant in GP. As a reaction to drought, BA showed reduced biomass under elevated CO₂, which was not seen in GP. Grain yield and harvest index (HI) were negatively influenced by drought and increased by CO₂ enrichment. BA formed higher grain yield and had higher water‐use efficiency of grain yield and HI compared to GP. CO₂ fertilization compensated for the negative effect of drought on grain yield and HI, especially in GP. Stomatal conductance proved to be the gas exchange parameter most sensitive to drought. Photosynthetic rate of BA showed more pronounced reaction to drought compared to GP. Overall, BA turned out to respond more intense to changes in water supply and CO₂ enrichment than the older GP.     

The Alleviating Effect of Elevated CO2 on Heat Stress Susceptibility of Two Wheat (Triticum aestivum L.) Cultivars

This study analysed the alleviating effect of elevated CO₂ on stress‐induced decreases in photosynthesis and changes in carbohydrate metabolism in two wheat cultivars (Triticum aestivum L.) of different origin. The plants were grown in ambient (400 μl l^?1) and elevated (800 μl l^?1) CO₂ with a day/night temperature of 15/10 °C. At the growth stages of tillering, booting and anthesis, the plants were subjected to heat stress of 40 °C for three continuous days. Photosynthetic parameters, maximum quantum efficiency of photosystem II (PSII) photochemistry (F_v/F_m) and contents of pigments and carbohydrates in leaves were analysed before and during the stress treatments as well as after 1 day of recovery. Heat stress reduced P_N and F_v/F_m in both wheat cultivars, but plants grown in elevated CO₂ maintained higher P_N and F_v/F_m in comparison with plants grown in ambient CO₂. Heat stress reduced leaf chlorophyll contents and increased leaf sucrose contents in both cultivars grown at ambient and elevated CO₂. The content of hexoses in the leaves increased mainly in the tolerant cultivar in response to the combination of elevated CO₂ and heat stress. The results show that heat stress tolerance in wheat is related to cultivar origin, the phenological stage of the plants and can be alleviated by elevated CO₂. This confirms the complex interrelation between environmental factors and genotypic traits that influence crop performance under various climatic stresses.     

Effect of water deficit in different growth stages on stem sap flux of greenhouse grown pear-jujube tree

The effects of water deficit in different fruit growth stages on the variation of stem sap flux of 6-year old greenhouse-grown pear-jujube trees were investigated. Treatments included sufficient water supply during the whole fruit-growing period (T₁), mild water deficit during the flowering–fruit setting stage (T₂), moderate water deficit during the fruit rapid growth stage (T₃) and severe water deficit during the fruit maturing stage (T₄). Results showed that significant compensation effect on stem sap flux after re-watering was observed in T₂, but not in T₃ and T₄ stages. At the end of rapid growth stage, the diurnal variation of stomatal conductance generally had a similar trend as that of stem sap flux, but with a distinct midday depression from 12:00 to 14:00 p.m. In addition, a linear relationship between the relative available soil water content (RAWC) and the ratio of daily stem sap flux to that of sufficient water treatment was observed (R² = 0.4489).