Leaf recruitment and elongation: an adaptive response to flooding in Villarsia reniformis

Villarsia reniformis (Menyanthaceae) responds to flooding by rapid leaf elongation and continual recruitment of young, submerged leaves (4.3–6.5 per week). Leaf production is influenced by nutrient availability and water depth. Leaves are submerged and die as the water level rises, but are replaced by younger leaves able to broach the surface. Young petioles may elongate at more than 10 cm per day, but lose the ability to elongate after the blades are exposed to air more than twice. Young petioles produce new cells and existing cells elongate, but in older petioles fewer new cells are produced and cell elongation, whilst limited, is the main mechanism for petiole elongation. Continual recruitment implies a high cost for production of structural tissue, but ensures that leaves capable of rapid extension are within reach of the water surface and the plants can respond quickly to flooding.     

川芎高频再生体系的建立

为建立川芎(Ligusticum chuanxiong Hort.)高频再生体系,优化了诱导和分化培养基及培养条件.以叶柄为外植体,以MS为基本培养基,KT2.0 mg/L+ IAA0.5mg/L的激素组合对不定芽分化最有利.在此基础上,针对外植体来源、培养条件和愈伤组织继代时间3个因素进行优化.结果表明:采用川芎无菌苗叶柄作为外植体,黑暗条件下诱导出愈伤组织,再在光照下继代培养15d后转入分化培养基中对不定芽诱导最为有利,分化率为44.4％.分化后得到的不定芽在含NAA0.5 mg/L和IBA 0.5 mg/L的1/2MS培养基上生根率达90％,移栽存活率为95％.     

布迪椰子不同器官热值的季节变化研究

对布迪椰子的幼叶、成熟叶、叶柄和根在不同季节的干重热值、去灰分热值和灰分含量进行了研究,结果表明:干重热值四个季节的平均值为成熟叶(20.65kJg-1)>幼叶(19.84kJg-1)>根(19.55kJg-1)>叶柄(18.77kJg-1),秋季的干重热值明显高于其它三个季节的干重热值,冬季的干重热值最低,去灰分热值与干重热值的变化趋势基本相同。灰分含量四个季节的平均值为根(5.14%)>叶柄(4.33%)>幼叶(4.21%)>成熟叶(3.97%)。成熟叶的灰分含量一直维持在比较低的水平,而幼叶的在秋季明显下降,在冬季明显上升,幼叶灰分含量的季节变化趋势与成熟叶的相同,叶柄灰分含量在冬季明显低于根部。布迪椰子这种不同器官在不同季节的热值和灰分的变化规律显示其具有较强的耐寒适应性。     

凹唇姜属(Boesenbergia O.Kuntze)和山柰属(Kaempferia L.)(姜科)叶的解剖学

通过凹唇姜属（Boesenbergia curtisii,B.Prainana,B.rotunda和B.plicata)和山柰属（Kaempferia pulchra,D.galanga.K.gilbertii,K.rotunda,K.parviflora和K.angustifolia)种间叶解剖学变化的研究,寻找能用于鉴别种的解剖学特征,结果显示变化表现在气孔的类型,中脉的结构,叶缘和叶柄横切面轮廓,叶片的远 轴面或近轴面下皮层和毛状体的出现或缺如,研究表明这些特征的联合对已研究的种的鉴别是有用的。     

川芎高频再生体系的建立

为建立川芎(Ligusticum chuanxiong Hort.)高频再生体系,优化了诱导和分化培养基及培养条件。以叶柄为外植体,以MS为基本培养基,KT 2.0 mg/L+IAA 0.5 mg/L的激素组合对不定芽分化最有利。在此基础上,针对外植体来源、培养条件和愈伤组织继代时间3个因素进行优化。结果表明:采用川芎无菌苗叶柄作为外植体,黑暗条件下诱导出愈伤组织,再在光照下继代培养15 d后转入分化培养基中对不定芽诱导最为有利,分化率为44.4%。分化后得到的不定芽在含NAA 0.5 mg/L和IBA 0.5 mg/L的 1/2MS培养基上生根率达90%,移栽存活率为95%。     

Uptake and distribution of phosphorus in tomato plants

Summary The uptake and distribution of phosphorus was examined in tomato plants, cv. Kirdford Cross, grown in peat to which phosphate was added (P₂) or omitted (P₁). The plants received a liquid feed containing either a high (N₂) or low (N₁) concentration of ammonium nitrate. Initially, all plants were grown in peat containing an intermediate level of phosphate.There was a rapid net export of P from the leaves of plants transferred to the P₁ medium resulting in deficiency symptoms before the fruit on the first truss had ripened. Most of the P absorbed by 11-week-old plants in the N₁P₂ and N₂P₂ treatments was located in the developing fruit, in the laminae of the mature leaves and in the lower parts of the stem. In the P₁ treatments, the lowest fruit truss was the dominant sink for the limited supply of P, but there was also a significant concentration of P in the shoot apex and in the laminae. Increasing the supply of N to plants in the P₂ treatment promoted the transport of P to the shoot and to the fruit trusses and also increased the total P uptake. However, plants in the N₂ treatment required a significantly higher level of tissue P to prevent the symptoms of P deficiency occurring in the laminae. Generally, symptoms occurred in laminae of mature leaves containing less than 0.13 per cent P. Increases in concentration of tissue P in response to raising the level of applied P were greatest in the petioles of the mature leaves, and it is suggested that these petioles are the most suitable tissues for the assessment of the P status of tomato plants.     

A high affinity pyruvate decarboxylase is present in cottonwood leaf veins and petioles: A second source of leaf acetaldehyde emission?

Considerable evidence indicates that acetaldehyde is released from the leaves of a variety of plants. The conventional explanation for this is that ethanol formed in the roots is transported to the leaves where it is converted to acetaldehyde by the alcohol dehydrogenase (ADH) found in the leaves. It is possible that acetaldehyde could also be formed in leaves by action of pyruvate decarboxylase (PDC), an enzyme with an uncertain metabolic role, which has been detected, but not characterized, in cottonwood leaves. We have found that leaf PDC is present in leaf veins and petioles, as well as in non-vein tissues. Veins and petioles contained measurable pyruvate concentrations in the range of 2 mM. The leaf vein form of the enzyme was purified approximately 143-fold, and, at the optimum pH of 5.6, the K_m value for pyruvate was 42 μM. This K_m is lower than the typical millimolar range seen for PDCs from other sources. The purified leaf PDC also decarboxylates 2-ketobutyric acid (K_m = 2.2 mM). We conclude that there are several possible sources of acetaldehyde production in cottonwood leaves: the well-characterized root-derived ethanol oxidation by ADH in leaves, and the decarboxylation of pyruvate by PDC in leaf veins, petioles, and other leaf tissues. Significantly, the leaf vein form of PDC with its high affinity for pyruvate, could function to shunt pyruvate carbon to the pyruvate dehydrogenase by-pass and thus protect the metabolically active vascular bundle cells from the effects of oxygen deprivation.