Phosphorus concentrations in the leaves of defoliated white clover affect abscisic acid formation and transpiration in drying soil

Increased leaf phosphorus (P) concentration improved the water-use efficiency (WUE) and drought tolerance of regularly defoliated white clover plants by decreasing the rate of daily transpiration per unit leaf area in dry soil. Night transpiration was around 17% of the total daily transpiration. The improved control of transpiration in the high-P plants was associated with an increased individual leaf area and WUE that apparently resulted from net photosynthetic assimilation rate being reduced less than the reductions in the transpiration (27% vs 58%). On the other hand, greater transpiration from low-P plants was associated with poor stomatal control of transpirational loss of water, less ABA in the leaves when exposed to dry soil, and thicker and smaller leaf size compared with high-P leaves. The leaf P concentration was positively related with leaf ABA, and negatively with transpiration rates, under dry conditions ( P < 0.001). However, leaf ABA was not closely related to the transpiration rate, suggesting that leaf P concentration has a greater influence than ABA on the transpiration rates.     

Soil phosphorus fractionation and phosphorus-use efficiencies of tropical rainforests along altitudinal gradients of Mount Kinabalu, Borneo

We studied soil phosphorus (P) fractionation and P-use efficiencies (PUEs) of rainforests along altitudinal gradients (700–3100 m) on two types of parental rocks (sedimentary versus ultrabasic) on Mount Kinabalu, Borneo. Sedimentary rocks were known to contain more quartz (which does not adsorb P) than ultrabasic rocks. The pool (top 30 cm) of total P was always greater on sedimentary (ranging from 34.9 to 72.6 g m^–2) than on ultrabasic (9.0–29.2 g m^–2) rocks at comparable altitudes. Accordingly, the pools of organic P and labile inorganic P were always greater on sedimentary than on ultrabasic rocks. The pool of primary mineral, calcium P increased upslope from 1.7 to 4.3 g m^–2 on sedimentary rock, suggesting that the altitudinal sequence of the sites reflected a decreasing magnitude of soil weathering upslope. The pool of calcium P on ultrabasic rock did not vary consistently with altitude (1.2–2.8 g m^–2), probably reflecting the greater between-site variability of primary mineral P in parent rocks. When all sites were compared, the pool of most labile, bicarbonate-extracted inorganic P increased (ranging from 0.02 to 1.85 g m^–2) with increasing calcium P. Calcium P was therefore considered to be an important P source to the biota on Kinabalu. Gross patterns in the variation of PUE (indexed as the reciprocal of the P concentration in litter) were best explained by the pool size of actively cycling P (total P minus occluded inorganic P). PUE, however, demonstrated distinct altitudinal patterns to generate an intricate conrol of P use pattern by soil P pools and altitude. Received: 2 August 1998 / Accepted: 28 November 1999     

The intensity of respiration and heat emission from seedlings of Festuca pratensis (Hud.) and Hordeum vulgare L. during pathogenesis caused by Bipolaris sorokiniana (Sacc.) Shoem

The presented work was conducted on seedlings of spring barley and meadow fescue which differ in the degree of sensitivity to leaf spot pathogen Bipolaris sorokiniana (Sacc.) Shoem. The seedling reaction to inoculation with mycelium and conidia was examined in glasshouse conditions on the basis of respiration intensity and heat production. The leaf respiration was measured using Clark-type electrode, while heat emission was evaluated by means of isotermic microcalorimeter. The measurements were performed after 1, 3, 6, 10, 24, 48, 72, 168 and 240 hours since the inoculation moment. Leaves of meadow fescue were characterized by the most intense respiration at the 6^th hour, while barley leaves at the 24^th and 72^nd hour after inoculation. In the case of meadow fescue the greatest heat production was noted in the period between 24 and 168 hours after inoculation. Simultaneously, at the 48^th hour the smallest rate of respiration was observed. Barley leaves emitted the greatest amount of heat only in the first 3 hours of the pathogenesis. In these hours the smallest respiration rate was noted. The observed, opposing reaction of respiration intensity and heat emission in the infected seedlings of both species may illustrate a disorder in metabolic processes in plants during pathogenesis. The plants studied differed in the time of their reaction to pathogen attack: barley responded earlier in heat production, while fescue extended respiration rate in the first hours after inoculation. This is clearly observable, when coefficients of metabolic inefficiency (heat rates per mole O₂) are compared. In the case of barley the highest rates were noticed just after inoculation, whereas in fescue at the 48^th hour. In both species attack of pathogen caused high metabolic efficiency.     

光敏核不育水稻等位突变系的AFLP分析

通过对NK58S和NK58F这一对光敏核不育水稻等位突变系的AFLP分析,比较了AFLP,RAPD及RFLP检测DNA多态性的相对效率。结果表明,这三种分子标记的DNA多态性检出效率依次为AFLP>RAPD>RFLP;找出了水稻AFLP分析的最适反应条件;通过AFLP和集群混合分析(Bulked segregating analysis,BSA),筛选出了一批与水稻光敏核不育(PGMS)基因连锁的多态性AFLP产物,已完成了对4个多态性AFLP产物的克隆,Southern杂交证明其中2个为单拷贝顺序,另外2个为低拷贝顺序。对上述三种分子标记各自的优缺点及它们在DNA多态性检测中的适用之处进行了分析探讨。     

褐藻叶绿体的制备

在4℃条件下,采用CaCl₂溶液浸泡褐藻裙带菜（Undaria pinnatifida）的叶状体,观察CaCl₂溶液的浓度和浸泡时间对裙带菜叶绿体提取率及其荧光特性的影响.结果表明,裙带菜的叶状体经过CaCl₂溶液浸泡后,其叶绿体的提取率有明显地提高.根据裙带菜叶绿体的提取率和室温荧光发射光谱的测定结果,认为最适的方法是采用0.2 mol/L的CaCl₂溶液浸泡10 min.在这种条件下,裙带菜叶绿体的提取率是传统制备方法的5倍.室温荧光发射光谱的测定结果说明叶绿体的完整性较好.     

不同小麦品种的根系生理特性,磷的吸收及利用效率对产量影？…

不同小麦品种的分蘖数、叶片数、干物量与根系总吸收面积及活跃吸收面积呈正相关,在低磷处理的相关性均达到显著水平。此各品种收获得期的干物量及籽粒产量亦与株吸磷量及利用效率呈正相关。通过各因素的比较,鉴定出在低磷条件下可获较高产量的品种。     

磷高效基因型小麦对缺磷胁迫的根际适应性反应

采用奶箱分隔栽培试验法,进行了磷高效与磷低效小麦基因型根际土壤ＰＨ与有效磷变化的研究,结果表明：小麦根际土壤ＰＨ和有效磷含量皆明显低于外围土壤,表现出明显的根际效应特征;磷高效基因型小麦的根际ＰＨ和有效磷含量明显低于磷低效基因型,ＰＨ变异范围和磷素亏缺区也表现明显较大。为了进一步验证磷高效小麦基因型这的这一根际特征,同时进行了施用水溶性,枸溶性磷肥的试验研究,结果表明,以水溶性磷肥对根际ＰＨ和有效     

离子注入水稻愈伤组织提高农杆菌转化效率的初步研究

通过ＧＵＳ报告基因表达的组织化学染色分析,我们发现低能氮离子束注入水稻愈伤组织可显著提高根癌农杆菌介转基因效率,这为克服单子叶植物对根癌农杆菌不敏感性、提高遗传转化效率的研究提供了一条新的途径。     

干旱胁迫对水稻水分利用效率的影响

通过特殊自然干旱胁迫的方法,研究不同干旱胁迫对水稻的水分利用效率（ＷＵＥ）的影响,在一定供水量时,水稻的ＷＵＥ随供水量的增加而下降,但水稻旱种时,却因供水量过低,干旱胁迫严重,ＷＵＥ值为最低。不同品种的水稻ＷＵＥ存在较大的差异,抗旱性强的品种具有较高ＷＵＥ,因此选用具有较高ＷＵＥ的品种,是水稻节水栽培的关键。