Oscillatory Transpiration in a Cotton Plant: II. A MODEL

A generalized conceptual model of oscillatory transpirationin a cotton plant growing in a nutrient solution under constantenvironmental conditions is presented. The model is based uponthe results and observations of an experimental study and thecontemporary literature. It incorporates the values of parameters,of initial and boundary conditions, and of significant variablesin the transpiration stream. A non-linear coupling consistingof a hysteresis loop with a time-variant constraint acting betweenthe guard cell potential and stomatal resistance is proposed.Mathematical equations based upon the network variables weresolved via a simulation language (CSMP—IBM/360). The modelshowed gradually damped oscillations early in the light periodand sustained oscillations later in the light period. The resultingsimulation output agrees satisfactorily with pattern of oscillationsobserved in vivo. Root resistance changes through the day causedminimal effect on oscillation. The principal causal effect foroscillatory behaviour appeared to be due to stomatal effects.     

Oscillatory Transpiration in a Cotton Plant: I. EXPERIMENTAL CHARACTERIZATION

A resistance-capacitance model of oscillatory transpirationin a cotton plant under constant environmental conditions isdiscussed. Experimental results showed that a cotton plant exposedto a sudden and large evaporative demand went through a periodof self-adjustment indicating the presence of negative feedbackmechanisms. Phase relationships between flow in stem, leaf waterpotential, water uptake by roots, and leaf turgor were characterizedthrough the day. The water-based oscillatory processes are explainedthrough a proposed model based upon a hysteresis-controlledfunction and delayed coupling in the leaf component. The periodof oscillation was found to be about 30 min. Results also indicatedthat the lag between the transpiration and water uptake ratesduring oscillations was strongly influenced by the capacitanceof the leaf and that stem capacitance was negligible.     

棉花矮化突变体的遗传分析

陆地棉科遗２号×中棉完紫的种间杂交衍生后代群体中分离出一株矮秆小叶突变体,经多年选择育成了矮早棉１号。在北京气候条件下,矮早棉１号成熟时,株高只有４５ｃｍ,不到正常陆地棉的１／２。遗传分析揭示矮早棉１号的矮化早熟特性系由两对隐性基因控制,其基因符号定名为ｄ_１和ｄ_２,矮早棉１号为双隐性纯合子,基因型为ｄ_１ｄ_１ｄ_２ｄ_２。正常陆地棉ＴＭ－１、中棉所１２及中棉所１６均为显性纯合子,基因型为Ｄ_１Ｄ_１Ｄ_２Ｄ_２。控制棉花株高的两对基因Ｄ_１／ｄ_１和Ｄ_２／ｄ_２间表现重叠作用。矮早棉１号在棉花早熟育种中有重要价值。     

Cotton domestication: dramatic changes in a single cell

Investigations on the nature of genetic changes underpinning plant domestication have begun to shed light on the evolutionary history of crops and can guide improvements to modern cultivars. A recent study focused on cotton fiber cells tracks the dramatic genome-wide changes in gene expression during development that have accompanied selection for increased fiber yield and quality.     

Stomatal Opening as a Practical Indicator of Moisture Stress in Cotton

The response of stomata to varying soil moisture content was studied in cotton by means of a new type of porometer suitable for field work. The results showed that maximum stomatal aperture was only attained when soil moisture was near the upper limit of the so called “available range”. These results indicate the possibility of making practical use of the new type of porometer for the purpose of determining soil moisture deficiency under field conditions, thus aiding in irrigation practices.     

Demonstration of Aflatoxin Inhibitory Activity in a Cotton Seed Coat Xylan

An inhibitor of aflatoxin biosynthesis localized in the seed coats of developing cotton was partially purified and characterized. Aqueous extracts from 25-day postanthesis seed coat tissue inhibited aflatoxin (B(inf1)) production in liquid cultures of Aspergillus flavus AF13. Inhibition was concentration dependent, with a 50% effective dose of 173 (mu)g of crude extract per ml of medium. The inhibitor was neutral in charge. Two active fractions were obtained from crude preparations by gel filtration chromatography (BioGel P-100). The purest fraction eluted in the void volume. Carbohydrate composition analysis of this void volume inhibitor indicated a composition of xylose (>90%) and mannose. Aflatoxin production in vitro was inversely related to inhibitor concentration in the fermentation medium (log of aflatoxin versus log of [inhibitor]; r(sup2) = 0.82; P < 0.002). The void volume inhibitor had a 50% effective dose of 6.2 (mu)g/ml, a 28-fold purification of the inhibitor material. These data support the hypothesis that seed coat inhibitory activity is associated with a cottonseed-specific xylan.     

近30年我国棉花需水特征

利用1981—2010年我国棉花全生育期和各生育阶段降水资料,分析在不同年降水量保证率条件下,棉花全生育期降水和需水量的变化特征.结果表明: 我国棉花全生育期降水分布总体稳定少变,由南至北降水量递减;棉花全生育期需水量分布情况相似,新疆地区需水量较全国其他地方多;降水盈亏0毫米线在35° N附近,最大亏缺量在1000 mm左右,最大盈余量在800～1200 mm.各生育阶段需水量以下降趋势为主,尤其是开花-吐絮期更为明显,棉花全生育期需水量Kendall倾斜度为-3.6673～-0.3733.     

Phyllosphere of Cotton as a Habitat for Diazotrophic Microorganisms

Positive nitrogenase activities ranging from 0.18 to 0.78 nmol of C₂H₄ cm⁻² h⁻¹ were detected on the leaf surfaces of different varieties of cotton (Gossypium hirsutum L. and G. herbaceum L.) plants. Beijerinckia sp. was observed to be the predominant nitrogen-fixing microorganism in the phyllosphere of these varieties. A higher level of phyllosphere nitrogen-fixing activity was recorded in the variety Varalaxmi despite a low C/N ratio in the leaf leachates. Leaf surfaces of the above variety possessed the largest number of hairy outgrowths (trichomes) which entrapped a majority of microbes. Immersion of plant roots in nutrient medium containing ³²P_i led to the accumulation of label in the trichome-borne microorganisms, thereby indicating a possible transfer of nutrients from leaf to microbes via trichomes. Extrapolation of acetylene reduction values suggested that 1.6 to 3.2 kg of N ha⁻¹ might be contributed by diazotrophs in the phyllosphere of the variety Varalaxmi during the entire growth period.     

Population Dynamics of Belonolaimus longicaudatusin a Cotton Production System

Belonolaimus longicaudatus is a recognized pathogen of cotton (Gossypium hirsutum), but insufficient information is available on the population dynamics and economic thresholds of B. longicaudatus in cotton production. In this study, data collected from a field in Florida were used to develop models predicting population increases of B. longicaudatus on cotton and population declines under clean fallow. Population densities of B. longicaudatus increased on cotton, reaching a carrying capacity of 139 nematodes/130 cm³ of soil, but decreased exponentially during periods of bare fallow. The model indicated that population densities should decrease each year of monocropped cotton, if an alternate host is not present between sequential cotton crops. Economic thresholds derived from published damage functions and current prices for cotton and nematicides varied from 2 to 5 B. longicaudatus/130 cm³ of soil, depending on the nematicide used.     

Growth Promoting Effect of a Transpiration Suppressant on Cotton

The transpiration suppressant Tag 16 (polyethylene emulsion), which is known to form thin films on leaves, was sprayed on cotton plants grown under varying weather and soil moisture conditions. In hot, dry weather and under restricted water supply 10 and 15% solution of the original Tag 16 promoted extension growth and increased fresh and dry weight of plants. In hot, humid weather three sprays at weekly intervals did not have any effect on plant height, fresh and dry weight, leaf number and flowering.     

棕色棉和绿色棉遗传多样性的比较研究

选用240条随机引物,从中筛选出6条对棕色棉新彩1、新彩2和绿色棉新彩3、新彩4及47个彩色棉品种间杂种作了RAPD多态性分析,并在棕色棉、绿色棉和棕绿彩棉3个水平进行聚类和相似性分析。结果表明,棕色棉之间、绿色棉之间及棕绿彩棉之间的遗传距离和相似性差异不显著,它反映了棕、绿彩棉之间的遗传基础比较狭窄,遗传多样性水平相当。可能是因为共同的基础种质资源、相同的育种目标及相近的育种方法造成此结果。 Abstract:Genetic diversity analysis of brown cotton Xincai 1 and Xincai 2 and green cotton Xincai 3 and Xincai 4 and other 47 color cottons was conducted by the random amplified polymorphism DNA (RAPD) techniques,using 6 random primers.Cluster and similarity analysis of these cottons showed that the differences in genetic relationship and similarity among the brown cottons,green cottons and brown-green cottons are not remarkable.The results also reflect that the genetic bases of the brown and green cottons are narrow,and they are at the same genetic diversity level.These results are probably due to the same basic germplasms,the same breeding aims and the similar breeding approaches.     

陆地棉HB红花性状特异SCAR分子标记的开发

利用Operon系列引物筛选到1个与HB红花性状基因连锁的RAPD标记OPA15^1160,对差异条带进行克隆与核苷酸测序,根据测序结果设计SCAR引物,在HB红花近等基因系及其白花轮回亲本中进行PCR扩增程序优化和鉴定,筛选出一对引物可稳定扩增出与HB红花性状基因连锁的特异片段,获得了与HB红花性状基因紧密连锁的SCAR标记HB^-330。利用具黄色花瓣紫红色基斑的海岛棉与粉红花瓣的红叶棉等种质材料以7LHB红花近等基因系与白花轮回亲本杂交的F1、BC1F1、F2群体,对该SCAR标记的特异性与准确性进行了鉴定与验证,在红花植株中扩增出了330bp大小的片段而在白花植株中未扩增出,证明该标记准确性高、重复性好。HB红花是通过远缘杂交转自野生二倍体比克氏棉的性状,已成功地应用于性状标记杂交棉育种。该SCAR标记不仅为HB红花标记杂交种的纯度鉴定提供了有效技术手段,也为新品种保护提供了技术支持,促进了红花性状杂交种的分子标记辅助育种进程。