提高霍山石斛仿生态栽培成活率方法的研究

霍山石斛仿生态栽培成活率低下一直是制约其规模化发展的主要因素,本文在对影响霍山石斛栽培成活率因素进行分析的基础上,认为种苗繁殖方法的个体差异、炼苗后的适应性及栽培技术差异是影响成活率的主要原因,并提出在茎段组培解决霍山石斛种苗育苗质量后,解决炼苗期的炼苗质量和配套栽培技术的方法与思路,使得霍山石斛的仿生态栽培成活率得到质的提升,对科研和生产开发均具有重要的指导意义。     

美国红枫组培苗生根移栽试验

以美国红枫微茎段为试验材料,研究生根基质、炼苗时间、育苗基质、育苗穴盘类型等因素对美国红枫组培苗生根移栽影响。结果表明:用以草炭土为基质的培养基代替琼脂培养基对美国红枫生根率影响差异不大;生根后炼苗3d时的移栽成活率最高;以1号基质(进口草炭土∶珍珠岩=2∶1)为育苗基质的美国红枫组培苗移栽成活率最高且长势最好;以32孔的穴盘成活率较高,且便于后期养护管理。     

铁皮石斛组培苗移栽基质筛选试验

试验设松磷:木屑=1:1、松磷:木屑:山核桃壳=1:1:1、松磷:山核桃壳=1:1、松磷4种基质处理对铁皮石斛(Dendrobium officinale)组培苗成活率及生长情况的影响,结果表明:移栽540 d后,铁皮石斛组培苗成活率、单株分支数、茎长以基质松磷:木屑=1:1中最佳,分别为95.9%、9.9支/株和7 cm;在基质松磷:山核桃壳=1:1中茎粗最粗,达到0.5 cm,但在该基质中铁皮石斛组培苗成活率最低。     

米老排组培苗移植及其影响因素

为提高主要栽培珍贵树种米老排(Mytilaria laosensis)组培苗的移植成活率,以选育的优良无性系组培生根苗为材料,研究炼苗方式、基质、苗木规格、植后施肥及移植季节等对移植成活率和苗木生长发育的影响.结果表明:松盖炼苗3 d,出瓶苗高度大于2 cm,植后3 d喷施1 MS大量元素营养液是较好的处理,在大棚条件下移植,不带黄心土的轻基质和河沙都是适合基质,移植成活率90%以上,在大田条件下移植,以黄心土:泥炭土=1:1或黄心土:蛭石=1:1为基质移植成活率较高.移植季节以4月成活率最高,9月、10月其次,考虑到我国南方地区最佳造林季节为3—5月,为减少苗圃管理成本,米老排组培苗生产安排在9—10月出瓶移植是比较合理的选择.     

铁皮石斛在潞江干热河谷的集约化栽培

对铁皮石斛在潞江干热河谷的集约化栽培技术开展研究,结果表明:铁皮石斛在潞江干热河谷2-5月移栽成活率高,恢复生长快;驯化组培苗、扦插苗和未驯化组培苗(瓶苗)移栽成活率都超过90%,成活率差异不显著,但投产后产量差异较大,驯化组培苗极显著高于未驯化组培苗(瓶苗)和扦插苗,未驯化组培苗极显著高于扦插苗,从投资成本考虑建议用未驯化组培瓶苗做种苗;配方基质能够提高铁皮石斛产量,杉木皮+山基土+碎木屑+牛粪(1∶1∶1∶1)的配方基质产量最高。     

紫叶稠李组培苗生根及移栽研究

以紫叶稠李组培瓶苗为实验材料,研究了不同苗高、基部茎粗和不同植物生长调节剂以及不同基质对组培苗生根、移栽成活的影响,结果表明,组培瓶苗的苗高、基部茎粗和植物生长调节剂以及不同基质对组培苗生根、移栽成活有显著影响,选用瓶苗高为2.5～3.0cm,基茎粗0.06～0.1cm的苗接种到添加生长素IBA0.2mg/L和NAA0.5mg/L的基本培养基中生根,生根率可达86.13%,将生长健壮的生根苗移栽在细河沙、熟表土和草炭土基质上炼苗,成活率达93.3%。     

大叶栎容器育苗试验

对大叶栎容器育苗不同基质,芽苗移栽不同截根长度、不同发育期,苗生长期遮荫试验表明:芽苗移栽时截根留2～4 cm有利于苗木的生长;茎芽幼叶展开期移栽成活率高,达97.53在%;全光照育苗对苗木生长明显大于遮荫条件下生长苗木;黄心土基质的苗木成活率、苗高、根系数量及生物量均最高.     

铁皮石斛组培快繁技术

以铁皮石斛无菌苗的茎段为外植体,通过诱导丛生芽,进行壮苗生根,建立了一套快繁体系。结果显示,铁皮石斛试管苗在MS培养基中生长状况最好,当添加NAA的浓度为0.1 mg/L,6-BA的浓度为2.0 mg/L时,铁皮石斛丛生芽的增殖率达到最高。铁皮石斛幼苗壮苗的较佳培养基为MS+0.5 mg/L IBA+0.5 mg/L NAA。同时,单独使用0.5 mg/L NAA的培养基中小苗生根快,根数多。香蕉泥能促进幼苗根系的生长。组培苗移栽到纯树皮的基质中,成活率最高。     

桃儿七组织培养苗炼苗移栽技术

从炼苗时间、移栽基质、移栽季节等方面对桃儿七组培苗炼苗移栽技术进行了研究。结果表明,一定范围内,炼苗时间越长组培苗移栽成活率越高,开瓶炼苗5d最适宜出瓶移栽;移栽基质选用草炭土与珍珠岩按2∶1比例混合,成活率最高,25～30d均有新叶和新根长出。在兰州地区,10—11月和3—4月适宜进行桃儿七组培苗的移栽,成活率最高达98.1%。移栽后10个月,植株生长健壮,根系发达。本研究结果为利用组织培养技术进行桃儿七的快速繁殖提供技术支撑。     

霍山石斛微体快繁技术研究

以霍山石斛茎段为外植体,利用MS或1/2MS作基本培养基研究不同浓度和比例的NAA、6-BA、KT、2,4-D、IBA对霍山石斛微体快繁的影响。结果表明,利用霍山石斛带节茎段作外植体,可以实现其微体快繁。1/2MS较MS作基本培养基更有利于外植体诱导出芽,且以1/2 MS+6-BA 1.0mg/L+NAA 1.0mg/L处理下丛芽平均芽数和诱导率最高,分别为2.45个和87%。丛芽增殖培养基配方以NAA 0.5mg/L+6-BA 0.8mg/L效果最佳,60d时增殖数和增殖倍数分别达到395和3.95。继代增殖培养基配方以MS+2,4-D 0.2mg/L+6-BA 0.8mg/L效果最佳,新增苗数和增殖倍数分别达到182和2.82。生根培养基配方以IBA 0.1mg/L+NAA 0.4mg/L效果最佳,平均根数、平均根长和生根率分别为7.0条、4.68cm和100%,且根系生长快,生长健壮。用经发酵的树皮作基质,霍山石斛组培苗较其他基质生长健壮、生长速度快,成活率达到92%。     

Effects of xylem cavitation and freezing injury on dieback of yellow birch (Betula alleghaniensis) in relation to a simulated winter thaw

Shoot dieback, shoot growth, stem xylem cavitation, stem and root freezing injury, and root pressure were measured in 2-year-old, cold-hardened, potted yellow birch (Betula alleghaniensis Britt.) seedlings that had been subjected to a simulated winter thaw for 0, 5, 10, 19 or 27 days followed by 10 weeks at -10 degrees C. Stem xylem cavitation was determined as percent loss of hydraulic conductivity. Stem freezing injury was measured as electrolyte leakage (EL). Root freezing injury was determined by EL and by triphenyl tetrazolium chloride (TTC) reduction. Thaw duration was significantly correlated with dieback, new shoot growth, stem xylem cavitation, stem and root freezing damage, and root pressure (P < 0.05). In particular, shoot dieback was positively correlated with stem xylem cavitation (P < 0.001), residual stem xylem cavitation (P < 0.01) and root freezing injury (P < 0.010), but only weakly correlated with stem freezing damage (P < 0.05). In roots, freezing damage was negatively correlated with root pressure (P < 0.05), which, in turn, was negatively correlated with residual stem xylem cavitation after root pressure development. In stems, there was no correlation between freezing damage and xylem cavitation. We conclude that long periods of winter thaw followed by freezing resulted in freezing injury to roots concomitant with a reduction in root pressures, leading to poor recovery from freezing-induced xylem embolism.     

Effect of nitrogen fertilizer on biomass production and nodulation behavior of Pongamia pinnata Pierre seedlings under nursery conditions

At the seedling stage, a small amount of N is required to boost growth of leguminous plants. A pot experiment was conducted to observe the effect of N fertilizer on various growth parameters and nodulation behavior of Pongamia pinnata under nursery conditions. After the establishment of seedlings, four nitrogen treatments, 0, 40, 80 and 100 kg·ha^?1 N were applied in two equal splits. Monthly observations were taken for the morphological parameters viz. plant height, collar diameter, leaf number, root length, root shoot ratio, nodule number and weight per plant. Maximum plant height was recorded after application of N at 40 kg·ha^?1. Seasonally, the difference in collar diameter in rainy season was significantly higher than in winter or summer. However, more leaves were produced per plant at N-40 and N-100 treatments in winter and rainy seasons. Higher root length was recorded in rainy season than in winter or summer. Root biomass was higher than for stems or leaves. Seasonal effects of N-80 and N-40 treatments on leaf dry weight were significantly higher than for N-100 or N-0. Stem dry weight was higher at N-40 than at other treatments in winter and summer seasons. Root:shoot ratio was higher throughout winter to early summer. Nodule biomass was 2–3 times higher in rainy season compared to winter or summer. Maximum nodule number and biomass per plant were highest at N-40, followed by N-0, N-80 and N-100 treatments. New nodule formation started from June to the end of September. Maximum biomass per plant was recorded at N-40, followed by N-80, N-100 and N-0. Nitrogen treatment effect and seasonal behaviour interaction were not significant. Significantly higher numbers of nodules per plant were recorded in rainy season followed by summer and winter for all treatments. Higher nitrogen doses suppressed growth while lower doses promoted growth in Pongamia pinnata. Therefore, the lower nitrogen dose i.e., N-40 Kg·ha^?1 applied in two equal splits was suitable at the initial nursery stage for the increase in nodulation and biomass production.     

Dynamics of nonstructural carbohydrates and biomass yield in a fodder legume tree at different harvest intensities

Tropical tree fodder is harvested by frequent prunings, and resprouting depends on nonstructural carbohydrate reserves in the remaining tree parts. We studied the effects of three pruning intensities (removal of all leaves and branches leaving 1 m of stem once a year (T-12), or every 6 months (T-6), and about 50% pruning every 2 months (P-2)) on regrowth and the dynamics of soluble sugars and starch in the legume tree Gliricidia sepium (Jacq.) Walp. growing under humid tropical conditions in Guadeloupe, Lesser Antilles. Carbohydrates were sampled in roots, stems and branches. Among pruned trees, trees in the T-6 harvest regime had the highest leaf fodder yield (0.73 kg tree(-1) year(-1)). High litter loss reduced leaf yield of T-12 trees, but compared with the other treatments, T-12 trees produced the most branch biomass (3.43 kg tree(-1)). Among treatments, P-2 trees had an intermediate leaf fodder yield and the lowest branch production. Sucrose, glucose and fructose were the most common sugars in all biomass compartments. Mannose, pinitol and an unidentified cyclitol were relatively abundant in branches. Root sugar and starch concentrations were unaffected by harvest regime. There was a significant interactive effect of harvest intensity and regrowth time on stem sugar concentration. Stem starch concentration was highest in T-12 trees. After a year of fodder harvesting, whole-tree reserves of nonstructural carbohydrates were highest in T-12 trees; however, a larger proportion of reserves were located in roots and stems of T-6 and P-2 trees. These reserves, which were not lost in pruning and contributed to regrowth of G. sepium after pruning, may explain the relatively small effects of harvesting regime on soluble sugar and starch concentrations.     

Responses of xylem cavitation,freezing injury and shoot dieback to a simulated winter thaw in yellow birch seedlings growing in different nursery culture regimes

Seedlings of yellow birch originating from the same seed source were treated with two levels of fertilizers during two growing seasons. The lower level of fertilizers, such as 50 (11:41:08 N:P:K ratio), 100 (20:08:20) and 35 ppm of nitrogen (08:20:30) were applied as the starter, grower and finisher, respectively. The higher level ones consisted of 75, 150, and 100 ppm of nitrogen in the same fertilizers. After 2 years growth, seedlings treated with the higher level of fertilizers, had fewer lateral branches, greater height and larger stem diameter. After natural hardening from November to February, seedlings were subjected to 0, 5, 10, 19 and 27 days of a simulated winter thaw followed by 10 weeks at −10°C. After the thaw-refreeze treatments, series of measurements were carried out. Stem xylem cavitation and root freezing injury significantly increased with thaw duration regardless of levels of fertilizer treatments. Stem freezing injury also significantly increased with thaw duration in all stem segments of seedlings treated with the higher level of fertilizers, but only in the top segments for the seedlings provided with the lower level of fertilizers. However, seedlings treated with the higher level of fertilizers developed cavitation more quickly. After 1 month of growth in the greenhouse following the thaw and freeze treatment, both types of seedlings showed significant decrease in the length of new shoot growth and increase in percent length of shoot dieback with thaw duration. The length of new shoots, however, was always greater for the plants treated with the higher level of fertilizers. No difference of shoot dieback between the seedlings of the two different nursery treatments were observed. Correlation analyses showed that the length of new shoots was highly related to root and stem freezing injury, while dieback was best correlated with root freezing injury and stem xylem cavitation regardless of the levels of fertilizer treatments. It was concluded that (1) the higher level of fertilizer applied during the culture of yellow birch seedlings can accelerate xylem cavitation and dehardening in the stem following freeze–thaw events; (2) stem xylem cavitation was unlikely the cause of stem freezing injury; and (3) root freezing injury and stem xylem cavitation are the most reliable measurements for predicting dieback of potential planting stock, but both root and shoot freezing injury are relate well to regrowth of new shoots in stock exposed to prolonged thaw.     

Drought resistance of two hybrid Populus clones grown in a large-scale plantation

Poplar hybrids were grown with irrigation in a large-scale plantation to investigate the mechanisms underlying clonal differences in drought resistance. Beginning in spring 1992, Populus trichocarpa x P. deltoides (TD) and P. deltoides x P. nigra (DN) cuttings received 46, 76, or 137 cm year(-1) of irrigation to supplement the 18-20 cm of annual precipitation, and all trees received the same fertilization regime. Stem volume, assessed as the square of stem diameter at breast height times tree height (D(2)H), and water relations of the trees were studied from the end of their second growing season until the end of their fifth growing season. By the end of the second growing season, stem volume of Clone TD was 40-146% larger than that of Clone DN, but stem volume growth was independent of irrigation in excess of 46 cm year(-1) in both clones. During the third growing season, stem volume growth of both clones was limited by both the 46- and 76-cm irrigation treatments, so that by the end of the third growing season trees in the 46-cm irrigation treatment were only half the size of trees in the 137-cm irrigation treatment. These treatment differences were maintained through the fifth growing season. Although stem volumes of Clone TD trees in the 76- and 137-cm irrigation treatments were larger than the corresponding values for Clone DN trees at the end of the third growing season (1994), these clonal differences gradually decreased in subsequent years and were not detectable after 5 years, because stem volume relative growth rate of Clone DN was greater than that of Clone TD in all treatments. Although both clones exhibited similar predawn leaf water potentials, Clone DN typically maintained higher midday leaf water potentials, suggesting better stomatal control of water loss. Clonal and treatment differences in osmotic potential at full turgor were minimal and could not explain the clonal differences in drought resistance. Root density and root density to stem volume ratio increased more in response to moderate drought in Clone DN than in Clone TD, resulting in enhanced drought resistance (high stem volume growth rate under moderate drought conditions) and an increased capacity to withdraw water from the soil. We conclude that the greater drought resistance of Clone DN compared with Clone TD was the result of the maintenance of a more favorable water balance by stomatal regulation and greater carbon allocation to roots during the early stages of drought. However, the low root density to stem volume ratio in Clone DN growing in the 46-cm irrigation treatment suggests that severe water limitation restricted the preferential allocation of carbon to belowground tissues, so that both root and shoot growth were constrained by severe drought.     

Prediction of stem profile of Picea abies using a process-based tree growth model

We built a simple tree growth model for Norway spruce (Picea abies (L.) Karst.) that describes the biomass and stem radial growth of one tree in a stand. Growth is controlled by an external height growth function that accounts for site quality. Crown recession is represented by an empirical function that accounts for the limitation to crown development caused by mechanical contacts with neighboring trees. The model describes biomass growth based on carbon budget (photosynthesis, respiration and senescence) and carbon partitioning between foliage, stem and root compartments. An internal regulation is introduced based on a functional balance between crown and root development. Stem annual growth is distributed along the stem by means of an empirical rule. Stem profile is the final output of the model and can be used to check the overall consistency of the model and as an aid in wood quality studies. The underlying assumptions of the model are described.     

Fine root dynamics in organic and mineral soil layers of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> D. Don plantation

Fine root dynamics and root architecture were studied in the organic and mineral soil layers of a Cryptomeria japonica plantation. Fine root biomass (<1 mm) showed seasonal changes whereas fine root biomass (1–2 mm) was unchanged over the study period. Root tips were grouped into size classes based on root tip diameter, including <0.5, 0.5–1, and 1–2 mm. Root tip density (<1 mm) was significantly correlated with fine root biomass (<1 mm). Root tip density and fine root biomass (<1 mm) increased in summer and decreased in winter, and both showed a similar seasonal pattern. Root tip dynamics influenced fine root dynamics. Root architecture as expressed by branching intensity changed with root tip production and mortality. Branching intensity also showed a similar seasonal pattern of root tip density dynamics. Root tips of both <0.5 and 0.5–1 mm were mainly produced in the organic soil layer, while root tips of 0.5–1 mm were mainly produced in the mineral soil layer. Because of the high RT1 root tip production in the organic soil layer, branching intensity was higher in the organic soil than in the mineral soil layer during summer. Root tip dynamics influenced fine root dynamics and the architecture of root systems in both organic and mineral soil layers.     

樟子松切根育苗试验

对樟子松进行切根育苗试验,结果表明,机械切根苗苗木质量优于移植苗和留床苗。切根２０ｃｍ的苗高、地径分别比移植苗高９４ｃｍ和粗０２ｃｍ,大于１ｍｍ的侧根数量,平均比移植苗多１１８条,比留床苗多１０条。机械切根可使２年生樟子松产苗量,比人工移植提高２４２９％～３７１４％,每公顷增加收入１５２８５～３０１１１元。     

Morphology of the Structural Root System of Sitka Spruce 2. Computer Simulation of Rooting Patterns

In a previous paper (Henderson et al. 1983), it was suggestedthat the processes of root growth and development proceed witha geometric regularity and that, as a consequence, root distributionis further extended and spatially more even than if growth wereat random. We examine this hypothesis and the relative importanceof the component growth processes through computer simulationof a model for root distribution at a fixed time. Root segments were measured on 16 year trees and statisticaldistributions fitted to the occurrence of lengths, branchingfrequencies and growth directions. These distributions comprisethe model which assumes that a root system consists of a numberof first-order roots originating at the stem, a number of second-orderroots originating on first-order ones and so on. Each root includesa number of bends and lateral branching points and terminatesin either a fork or when diameter reaches 5 mm, smaller rootsnot being included. Parameter manipulation of the fitted distributions and furthersimulation showed that some regular growth mechanisms were necessaryfor the simulation of realistic rooting patterns. In particularit was important that direction changes at bends and of newroots at forks were typically small to ensure that the systemspread outwards, away from the stem. Lateral branches neededto subtend large angles to their parents in order to exploitseparate soil regions. Other necessary rules were that first-orderroots were almost regularly distributed around the stem andfor a tendency for azimuth changes at bends to be alternatelyclockwise then anticlockwise. Simulations were also used to examine the possibility of estimatingtotal root length from a study of only part of a root system.An example of excavating one quarter of the system is consideredand the results indicate that root systems may be so variablethat no reliable estimate can be obtained.