Seasonal variation in root growth capacity during cultivation of container grown Pinus sylvestris seedlings

Root growth capacity (RGC) in Scots pine seedlings was studied from the time of sowing and during the following two growing seasons. The method used for measuring RGC is also described. In the first growing season root growth was intense during the period mid‐July to mid‐September with an earlier peak for early sowing dates. After a period of low growth activity during winter, RGC rose sharply in early spring. During periods of intensive shoot elongation in May and June root growth was depressed. After shoot elongation was completed, RGC rose again before declining during the autumn. During winter and the second growing season, higher RGC levels were obtained for seedlings sown in June compared to the ones sown in April. This result is discussed with regard to differences in cultivation regimes.     

Freezing temperatures in the root zone—effects on growth of containerized Pinus sylvestris and Picea abies seedlings

Roots of 1‐year‐old containerized seedlings of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) were experimentally frozen in December. The seedlings were then grown for 3 weeks in a growth chamber and evaluated with regard to root growth capacity (RGC) and shoot elongation. The subsequent RGC of Scots pine declined as root zone temperatures were lowered from ‐6°C to ‐11°C and from ‐11°C to ‐16°C. Almost no root growth was observed after exposure to ‐20°C. Shoot growth was also negatively affected by low root temperatures but less than root growth. Low root temperatures did not affect Norway spruce as much as Scots pine, although root and shoot growth of Norway spruce were reduced after exposure to the lowest test temperatures (‐16°C and ‐20°C). The length of exposure, ranging between 1 and 8 hours had no effect on subsequent growth.     

Planting performance potential of Pinus sylvestris seedlings as evaluated by root growth capacity and triphenyl tetrazolium chloride reduction methods

Root growth capacity (RGC) and root viability by the reduction of triphenyl tetrazolium chloride (TTC) of Scots pine (Pinus sylvestris L.) seedlings were measured in the winter and spring after freeze‐induced stress (0, ‐10, ‐15, ‐20°C). After freezing, seedlings were also stressed with different storage temperatures, and drying. Field performance during two years at two sites was used to determine the prediction abilities of the two test methods. RGC and TTC differed between the winter and spring tests. Coefficients of variation (CV) for RGC were larger in the winter than in the spring. The opposite applied for TTC. RGC was significantly lower in the winter than in the spring. TTC reduction was lower in the spring than in the winter. RGC‐ and TTC‐values decreased as freezing temperatures were lowered. Correlation coefficients between treatment means of RGC and TTC were low. Coefficients of determination (r ²) of linear regressions of RGC to the field performance attributes, first and second year diameter increment, height increment, and survival, were between 0.30 and 0.40. For TTC the revalues ranged from 0.50 to 0.80. In general, the TTC‐method seemed to be a better indicator of Scots pine seedling performance in the field.     

Influence of nursery culture on western red cedar

Western red cedar (Thuja plicata Donn) seedlings were grown in a greenhouse and subjected to six nursery cultural treatments (long-day wet (LDW), long-day moderate (LDM), long-day dry (LDD), short-day wet (SDW), short-day moderate (SDM), and short-day dry (SDD)) during mid-summer. Seedling attributes were measured before fall and spring planting.Short-day and moisture stress treatments reduced shoot but not root growth, resulting in reduced shoot to root ratios. Fall tested LDW seedlings had a higher osmotic potential at saturation and turgor loss point than other treatments. Fall tested short-day seedlings had lower resistance to plant water movement. The LDW seedlings had the greatest new root growth in fall testing, while one of the lowest in spring testing. In the fall, LDW seedlings had the greatest net photosynthesis (P_n) at 25 °C root temperature, with all treatments having a similar decline in P_n as root temperatures decreased to 1 °C. In the spring, all treatments had a similar decline in P_n with decreasing predawn shoot water potential. Moisture stress and short-day nursery cultural treatments applied in mid-summer will not harden western red cedar seedlings for all potential field conditions.Spring, compared to fall, tested seedlings had two times the shoot and three times the root dry weight. Spring tested seedlings had a lower osmotic potential, maximum modulus of elasticity, relative water content at turgor loss point and greater dry weight fraction. Fall, compared to spring, tested seedlings had lower resistance to plant water movement and greater cuticular transpiration. In general, fall tested seedlings had more root growth than spring tested seedlings. Spring, compared to fall, tested seedlings generally had greater stress resistance.     

Damage caused by Lygus rugulipennis Popp. (Heteroptera,Miridae), to Pinus sylvestris L. seedlings

The tarnished plant bug (Lygus rugulipennis) and occasionally L. punctatus were found to feed on pine seedlings in central Finland. Both the nymphs and adults of Lygus bugs injured the apical meristem of the seedlings. This led to the death of the apex, and the opening of the lateral buds, resulting in a seedling with multiple leaders. L. rugulipennis may also oviposit on pine seedlings and the development from egg to adult on pine alone is possible. In laboratory experiments it was shown that the main factor in the apical meristem injury is the mechanical damage caused by the bug's stylet. The feeding damage and artificial mechanical damage caused by needles to the apical meristem of pine seedlings resulted in increased numbers of multiple‐leader seedlings and reduced shoot length and dry weight of the shoot and root.     

Root water flow and growth of aspen (Populus tremuloides) at low root temperatures

Effects of root zone temperature on growth, shoot water relations, and root water flow were studied in 1-year-old aspen (Populus tremuloides Michx.) seedlings. Seedlings were grown in solution culture and exposed to day/night air temperatures of 22/16 degrees C and solution culture temperatures of 5, 10, or 20 degrees C for 28 days after bud flush. Compared with root growth at 20 degrees C, root growth was completely inhibited at 5 degrees C and inhibited by 97% at 10 degrees C. The 5 and 10 degrees C treatments severely reduced shoot growth, leaf size, and total leaf area. Root water flow was inhibited by the 5 and 10 degrees C treatments. However, when seedlings were grown for 28 days at 5 degrees C and root water flow was measured at 20 degrees C, there was an increase in flow rate. This increase in root water flow was similar in magnitude to the decrease in root water flow observed when seedlings were grown for 28 days at 20 degrees C and root water flow was measured at 5 degrees C. Reduced root water flow of seedlings grown at 5 and 10 degrees C resulted in decreased stomatal conductance, net assimilation, and shoot water potentials. Root water flow was positively correlated with leaf size, total leaf area, shoot length, and new root growth. Transferring seedlings from 5 to 20 degrees C for 24 h significantly increased root water flow, shoot water potential, and net photosynthesis, whereas transferring seedlings from 10 to 20 degrees C resulted in only a slightly increased shoot water potential. Transferring seedlings from 20 to 5 degrees C greatly reduced root water flow, stomatal conductance, and net photosynthesis, whereas shoot water potential decreased only slightly.     

Drought tolerance and transplanting performance of holm oak (Quercus ilex) seedlings after drought hardening in the nursery

Drought stress is the main cause of mortality of holm oak (Quercus ilex L.) seedlings in forest plantations. We therefore assessed if drought hardening, applied in the nursery at the end of the growing season, enhanced the drought tolerance and transplanting performance of holm oak seedlings. Seedlings were subjected to three drought hardening intensities (low, moderate and severe) for 2.5 and 3.5 months, and compared with control seedlings. At the end of the hardening period, water relations, gas exchange and morphological attributes were determined, and survival and growth under mesic and xeric transplanting conditions were assessed. Drought hardening increased drought tolerance primarily by affecting physiological traits, with no effect on shoot/root ratio or specific leaf mass. Drought hardening reduced osmotic potential at saturation and at the turgor loss point, stomatal conductance, residual transpiration (RT) and new root growth capacity (RGC), but enhanced cell membrane stability. Among treated seedlings, the largest response occurred in seedlings subjected to moderate hardening. Severe hardening reduced shoot soluble sugar concentration and increased shoot starch concentration. Increasing the duration of hardening had no effect on water relations but reduced shoot mineral and starch concentrations. Variation in cell membrane stability, RT and RGC were negatively related to osmotic adjustment. Despite differences in drought tolerance, no differences in mortality and relative growth rate were observed between hardening treatments when the seedlings were transplanted under either mesic or xeric conditions.     

云杉幼树根系分泌物对2种草本植物种子萌发和幼苗生长的影响

【目的】探究西南亚高山人工针叶林主要造林树种粗枝云杉根系分泌物输入对林下草本植物种子萌发和幼苗生长的影响,揭示根系分泌物对林下植被更新和群落多样性的潜在生态效应。【方法】通过前期在野外原位收集根系分泌物,后期在实验室人工添加的方式,从种子萌发、幼苗生物量、幼苗形态3个方面来探究根系分泌物对西南亚高山人工云杉林生境内的2种草本植物白车轴草[JP2]和紫花苜蓿的影响。【结果】1)在种子萌发方面,根系分泌物添加降低了2种草本植物的种子发芽率、发芽势和发芽指数,且紫花苜蓿种子在处理间差异显著。2)在幼苗生物量方面,2种草本植物幼苗鲜质量、干质量在根系分泌物处理下均呈下降趋势,而且紫花苜蓿幼苗处理间差异显著。3)在幼苗形态特征方面,根系分泌物添加降低了2种草本植物的总长度、总表面积、总体积,且幼苗总长度处理间存在显著差异。4)根系分泌物处理下,2种草本植物的各项化感效应指数(RI值)均小于0,而且根系分泌物处理造成的2种植物化感效应综合指数(SE值)小于0,表明根系分泌物添加对2种草本植物种子萌发和幼苗生长均具有抑制作用,且对紫花苜蓿种子的抑制作用更强。5)UPLC-MS分析表明,云杉幼树根系分泌物中检测出多种酚酸类物质。【结论】云杉幼树根系分泌物输入对林下草本植物种子萌发及幼苗生长均产生了抑制效应。根系分泌物中的酚酸类物质可能是导致根系分泌物处理下草本植物种子萌发和幼苗生长受到抑制的内在驱动机制。     

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.     

Configuration and development of root systems of cuttings and seedlings of Eucalyptus globulus

Stem cuttings of Eucalyptus globulus are used within tree improvement programs and for mass deployment. To be successful, cuttings must perform as well or better than seedlings. The root systems of cuttings are fundamentally different from those of seedlings. If these differences influence growth, the differences and their consequences must be identified and the propagation system manipulated to improve performance of the propagules.Cuttings are only a viable alternative to seedlings as planting stock if the method of propagation does not affect their growth and development adversely. Full-sibling cuttings and seedlings of Eucalyptus globulus were compared under controlled environmental conditions to minimise extraneous sources of variation, and to establish whether changes in growth or development were induced by propagation. On three occasions over a period of eight weeks root-collar diameter, shoot height, leaf and stem weight, shoot/root ratios and root system morphology were measured on cuttings and seedlings. Seedlings were taller than cuttings throughout the experiment, but both plant types had similar height growth rates. Diameter growth rates were lower in cuttings than seedlings, and there were differences in both height and diameter growth rates between families. Root system configuration differed between the plant types. Seedlings had strongly gravitropic tap-roots, with two types of primary roots from which secondary roots emerged. Cuttings had no tap roots, and the main structural components of their root systems were adventitious roots formed during propagation. Cuttings did not develop further structural roots during the experiment, whereas seedlings continued to develop primary roots. Individual primary roots of cuttings were longer and had larger mid-point diameters than those of seedlings, but the total length of primary roots was greater in seedlings. Seedlings also had a greater number and total length of secondary roots. Shoot/root ratios, calculated from a range of functional measures, were higher in cuttings than seedlings.     

红椆播种苗移栽容器育苗技术研究

为提高红椆苗木质量和造林成活率,对红椆2年生直播苗和2年生撒播苗移栽容器苗苗木质量进行对比试验,同时采用不同规格容器和遮荫处理对1年生撒播苗移栽到容器后苗木的成活率和生长量进行比较试验。结果表明:容器育苗可显著提高红椆苗苗高、地径、主根长、地上部分干重、地下部分干重;容器规格对移栽后苗木成活率影响不显著,但对苗木生长有显著影响;采用80%遮阳网遮荫,容器苗成活率较高,苗木高生长也显著增加,但苗木地径生长与60%遮阳网遮荫处理的苗木差异不显著。     

Effects of a deep container on morpho-functional characteristics and root colonization in Quercus suber L. seedlings for reforestation in Mediterranean climate

In the last decades, reforestation and afforestation programs are being carried out mainly with containerized seedlings. Container design determines the morphological and physiological characteristics of seedlings. However, container characteristics are often the same for plant species with very different growth strategies. The most commonly used nursery containers are relatively shallow and limit tap root growth; consequently, species relying on the early development of a long tap root to escape drought, such as those of the Quercus genus, might need to be cultivated in deep containers. The aim of this paper was to compare the morphological and physiological characteristics of Quercus suber L. seedlings cultivated in shallow containers (CCS-18, depth 18 cm) with seedlings cultivated in deep containers (CCL-30, depth 30 cm). Both container types used were made of high-density polyethylene, cylindrical in shape, open-bottomed, with a diameter of 5 cm, two kinds of vertical ribs on the inside wall showing a cultivation density of 318 seedlings/m². At the end of nursery culture, the seedlings cultivated in the CCL-30 deep container presented a longer tap root, higher shoot and root biomass and higher Dickson Quality Index (DQI). Moreover, the CCL-30 seedlings showed a higher root growth capacity (RGC), they reached deep substrate layers faster and they presented higher root hydraulic conductance. These morpho-functional advantages improved the CCL-30 seedling water status, which was expressed by higher stomatal conductance during an imposed drought period.     

Growth and nutrition of containerized Pinus Resinosa seedlings at varying moisture regimes

Containerized red pine (Pinus resinosa Ait.) seedlings were grown over a 16-week rotation at different irrigation treatments to assess moisture stress on plant growth and nutrition, and to evaluate container capacity as a guide for irrigation. Wet, moist and dry moisture regimes were induced by watering trees to the container capacity weight of the growing medium after declining to respective 92, 73 and 57% of this reference weight. The seedlings received the same amount of fertilizer over the growth period. Maximum shoot and root growth was attained under the wet moisture regime, but biomass was reduced 21 and 43% for the moist and dry regimes. Plant nutrient concentrations were not significantly affected by watering treatment, and vector diagnosis of dry matter production and element composition indicated that macronutrients were non-limiting. Seedling nutrient uptake however, was significantly diminished by moisture stress which was attributed to decreased root growth and lower mass flow and diffusion of nutrients when moisture availability was reduced in the peat rooting media. Container capacity was found to be a sensitive reference for judging the watering requirements of greenhouse-grown containerized seedlings. The method can be relatively easily applied on an operational basis.     

Storability measures of Norway spruce and Scots pine seedlings and assessment of post-storage vitality by measuring shoot electrolyte leakage

As indoor frozen storage is increasing in forest tree nurseries it is important to have accurate methods for assessing seedling storability in autumn and methods to determine post-storage vitality. Storability of spruce (Picea abies (L.) Karst.) and pine (Pinus sylvestris L.) seedlings can be based on determination of dry matter content (DMC) of seedling shoots or by freezing shoots at –25°C and thereafter measure electrolyte leakage (SEL_diff–25). To compare these two methods we stored 1-year-old spruce and pine seedlings at different occasions during the autumn. To test if leakage of electrolytes from shoots (SEL) could indicate deteriorated vitality, we measured SEL at the end of storage. After storage seedling viability was determined in a three-week growth test, measuring shoot and root growth capacity (RGC). Determination of freezing tolerance (SEL_diff–25) before storage had a better ability to predict the outcome of storage compared to the DMC test. Measuring SEL at the end of the frozen storage period accurately indicated seedling vitality. Seedlings with SEL of 0–5% had a high survival rate whereas SEL over 10% indicated low survival and growth capacity after storage. The SEL method has a potential to become a screening test for identifying batches of seedlings that have been damaged during storage in the nursery.     

Growth and mineral nutrition of Gmelina arborea Roxb. seedlings fertilized with four sources of nitrogen on a latosolic soil

The growth and mineral nutrition of Gmelina arborea Roxb. seedlings were investigated in response to four nitrogen-based fertilizers applied at 0, 2.5, 5.0 or 7.5 g N per plant. Nitrogen sources included NH(4)-N as ammonium sulfate, NO(3)-N as potassium nitrate, NH(4)NO(3)-N as calcium ammonium nitrate, and urea-N as urea. Seedlings fertilized with NH(4)NO(3)-N or urea-N had greater height, collar diameter, dry weight, net assimilation rate, and relative growth rate than seedlings fertilized with NH(4)-N or NO(3)-N. For all sources of nitrogen, increasing the amount of exogenously supplied N per plant promoted shoot growth more than root development, hence the root to shoot ratios of all fertilized seedlings were smaller than those of the unfertilized controls. Applications of NO(3)-N increased the nitrogen, potassium, and phosphorus concentrations of fertilized seedlings. Regardless of source, a nitrogen application of 2.5 g N per plant was apparently optimal for the growth of Gmelina seedlings on a latosolic soil.     

Covariances between morphological characteristics in bareroot Pinus sylvestris nursery stock

In this study an attempt was made to gather information on the relationships of morphological attributes of bareroot Pinus sylvestris seedlings in order to determine the possible use of these attributes for grading purposes. The covariance structure of different morphological variables was studied in commercially produced crops. From each selected batch of Scots pine seedlings, 300 seedlings were sampled, three successive living seedlings from each of the 100 systematically selected sampling points ("clusters"). Variance in the seedlings crop was described using a linear model: total covariance was divided into variance between batches, between clusters and between individual seedlings (error).

Most of the correlations between different plant parts were large and positive. Only needle length and root length seemed to vary independently of other “length”; variables. Within one batch, at the end of the growing season, height‐diameter was more clearly size‐independent than shoot‐root ratio. Needle biomass increased exponentially with seedling height but the smallest seedlings had relatively less needle biomass than the biggest seedlings. It is not necessary to include dry mass in the requirements for seedling quality since it correlates well and can be described with other variables that can be measured more easily. Of the principal components for morphological characteristics, the “stem”; component explained 69% of the height variation and 77% of the diameter variation, the “needle”; component explaining 79% of the variation in current needle length, and the “root”; component 58% of the variation in root length. Together the three components explain 76% of the total variance in the original crops.     

Physiological and field growth responses of oak seedlings to warm storage

The effect of warm storage (15°C) for 0, 15 or 31 days, applied after cold storage until April, and date of lifting to cold storage on the physiological condition and field performance of two-year-old oak seedlings (Quercus robur L.) was investigated. Assessments before planting included plant moisture status, root and shoot dry weight, root growth potential (RGP), while after planting root growth, shoot growth phenology, shoot and root dry matter accumulation and stem quality were assessed. Warm storage effects were large, but lift date effects were small. Warm storage for 31 days reduced height and diameter growth, stem quality, total biomass, root growth, and reduced stem quality in the field, but 15 days storage had a smaller effect. Warm storage delayed bud break and shoot growth cessation but survival was unaffected. The depletion of food reserves during storage and low moisture availability might have caused shoot dieback leading to the development of poor quality stems. There was evidence that dry weight fraction of both the shoot tip and the taproot provided good information on the quality of the stock before planting. RGP was also a good indicator of quality. Electrolyte leakage readings from fine and taproots were not reliable indicators of plant quality.     

接种幼套球囊霉对干旱生境中构树幼苗根系形态的影响

利用WinRhizo根系分析系统,在石灰土基质上对不同土壤水分条件下接种丛枝菌根真菌幼套球囊霉对构树幼苗根系形态特征的影响进行了研究.结果表明:土壤水分状况和接种丛枝菌根真菌对构树幼苗生物量积累产生了显著的影响;构树幼苗根系干质量、总长度、表面积、体积、根节数目、根系平均直径均随着土壤含水量的降低而降低,幼套球囊霉则降低了同等水分条件下构树幼苗的比根长;土壤水分和接种幼套球囊霉同样也对根节平均长度产生了影响.     

Indole-3-butyric acid accelerates adventitious root formation and impedes shoot growth of Pinus elliottii var. elliottii?×?P. caribaea var. hondurensis cuttings

Many plantation tree species are cloned to achieve the growth, disease resistance and wood quality characteristics required for a successful economic venture. However, clonal propagation is limited by declines in adventitious root formation with increasing stock plant age. We examined the effects of immediate or delayed IBA application on adventitious root formation and subsequent root and shoot development of cuttings harvested from 8-year-old clonal hedge plants of Pinus elliottii var. elliottii × P. caribaea var. hondurensis. IBA applied at the time of setting accelerated root formation, elevating the percentage of cuttings with roots at 13 weeks post-setting from 45 to 78% and from 83 to 93% for a low- and a high-rooting clone, respectively. Final rooting percentages for the same treatments and clones (78 and 85%, and 88 and 100%, respectively, at 20 weeks post-setting) were not significantly affected by IBA application. IBA increased the root:shoot ratio of rooted cuttings by decreasing shoot weight compared with untreated cuttings, without affecting root weight, root length, root surface area or root volume. IBA was only effective when applied at the time of setting. A simple IBA treatment for cuttings from 8-year-old clonal hedges, by accelerating root production, has potential for reducing nursery costs and increasing the root system quality of containerised pine cuttings.     

工业和住宅污泥对大叶相思种子萌发以及幼苗生长参数的影响

在孟加拉国吉大港大学林业与环境科学院苗圃内,评价了污泥对大叶相思种子萌发以及幼苗生长的作用。播种前,将污泥与营养匮乏的自然林土壤按不同比率混合,分别在播种后的第1,2和3个月时,记录种子萌发情况和幼苗生长参数（枝条和根系的长度、直径、枝条的鲜重和干重、根和总的干物质量）。在播种前和幼苗采收后,分别测定各个处理的污泥-土壤混合物的理化参数（pH值、有机碳、氮、磷、钾）,以及重金属含量（铬、镍、锰、镉、锌）。结果表明,与对照相比,污泥-森林土壤混合物中播种的种子萌发率和幼苗生长参数发生显著变化。土壤-污泥按2：1混合时,种子萌发率最高（90%）,幼苗生长速率和生物量最大,有机碳和氮磷钾含量也最高。混有工业污泥的土壤中重金属含量要高于混有住宅污泥的土壤。在工业污泥土壤中,污泥-土壤按1：1混合时,重金属含量最高。据此推荐,在退化森林土壤中,土壤-污泥以2：1混合较适合大叶相思种子萌发和幼苗生长。