巴西橡胶树初生乳管黄色体微纤维蛋白质与67kD蛋白质的关系

在古铜期的巴西橡胶（Hevea brasiliensis Mull.Arg)幼茎初生乳管黄色体中存在丰富的微纤维蛋白质。在电子显微镜下,微纤维蛋白质呈两种不同的形态,分别存在于不同的黄色体中,SDS-PAGE分析表明,经等电点纯化的微纤维蛋白质的主要成分是59.5kD和63.5kD蛋白质,使用67kD蛋白质的抗血清的免疫印迹表明,59.5kD和63.5kD蛋白质与积累在贮藏蛋白质细胞中的67kD蛋白质具有一定程度的免疫相关性,且在苗生长发育过程中互为消长,59.5kD和63.5kD蛋白质在古铜期的幼茎中最丰富,当新梢茎停止伸长及叶片刚成熟时,其含量略有降低,但在第二和第三伸长单位中明显消失,同时在黄色体中大量积累3-5种低分子量蛋白质。这种季节变化模式表明,59.5kD和63kD蛋白质的消失与新梢的伸长生长无关,与初生乳管的发育关系密切,67kD蛋白质在古铜期的幼茎中不存在,随着新梢的成熟,该蛋白质不断积累,表现为典型的营养贮藏蛋白质。     

A role for nitrogen reserves in forage regrowth and stress tolerance

Carbohydrate accumulation and utilization during shoot regrowth after defoliation and winter has been studied extensively in most species used as forage. However, recent work suggests that N reserves found in vegetative tissues also are important for defoliation tolerance and winter hardiness. Results suggest that these N reserves constitute an alternative N source used when N₂ fixation and/or mineral N uptake are reduced. ¹⁵N labelling experiments indicate that a large proportion of herbage N is derived from N reserves mobilized from stem bases or roots to developing leaves and shoots. Amino acids and specific proteins (i.e. vegetative storage proteins, VSPs) are deposited in roots and stem bases and, in the case of VSPs, are degraded rapidly after defoliation. Identification and characterization of VSPs will increase our understanding of the role N reserves play in stress tolerance and may lead to innovative approaches for improving forage persistence and productivity.     

Precociously germinating rapeseed embryos retain characteristics of embryogeny

We compared the germination of Brassica napus L. embryos at three stages of development-mid-cotyledon, maturation and mature dry-to determine at which stage they acquired the capacity for normal germination and seedling development. Embryos were removed from the seed and cultured on hormone-free medium, allowing them to germinate. The transition from embryogeny to germination was monitored both morphologically and biochemically, using synthesis of 12 S storage protein as a marker of embryogeny. The mature embryos (dry seeds) set the standard for normal seedling development: radicle emergence, hypocotyl extension and cotyledon expansion occurred within 2 d and true leaves were formed within a week of germination. Rocket immunoelectrophoresis indicated that the storage proteins in seedlings from mature dry embryos were completely degraded within a week. In contrast, the midcotyledon-stage embryos appeared to germinate abnormally, retaining many embryonic characteristics. Although the roots emerged, the hypocotyls did not elongate and secondary cotyledons instead of leaves were formed at the shoot apex. Also, the seedlings continued to synthesize and accumulate storage proteins. The maturation-stage embryos did develop into normal-looking seedlings, but complete degradation of storage proteins required several weeks, presumably reflecting continued synthesis and turnover. We conclude that embryogenic and germination-specific processes can occur concurrently and that the capacity to develop as normal seedlings is acquired gradually during the maturation process.Abbreviations dpa days post anthesis - EDTA ethylenedi-aminetetraacetic acid - FW fresh weight     

Vegetative storage protein in Litchi chinensis, a subtropical evergreen fruit tree, possesses trypsin inhibitor activity

BACKGROUND AND AIMS: Vegetative storage proteins (VSPs) are commonly bioactive in herbaceous plants but few VSPs with bioactivity have been identified in trees. In addition, information on the characterization of VSPs in evergreen trees is limited. The objective of this study was to characterize the VSPs with bioactivity in evergreen trees. Methods The VSP in lychee (Litchi chinensis), an evergreen fruit tree, was characterized by a combination of cytological, biochemical and molecular biological techniques. KEY RESULTS: The VSP in lychee was a 22-kDa protein. It accumulated in the large central vacuoles of protein-storing cells (PSCs) in two distinguishable forms, granular and floccular. The PSCs were of a novel type. The 22-kDa protein is distributed in mature leaves, bark tissues of branches, trunk and large roots, paralleling the distribution of PSCs. Its homologues were present in mature seed. During young shoot development and fruiting, the 22-kDa protein decreased apparently, suggesting a nitrogen-storage function. The 22-kDa protein had several isoforms encoded by a small multigene family. One gene member, LcVSP1, was cloned. The LcVSP1 had no intron and contained a 675 bp open reading frame encoding a putative protein of 225 amino acids. LcVSP1 was homologous to Kunitz trypsin inhibitors. The 22-kDa protein inhibited trypsin and chymotrypsin, but had no inhibitory effect on subtilisin. CONCLUSIONS: Lychee is rich in a 22-kDa VSP with trypsin inhibitor activity. The VSP plays an important role in nitrogen storage while its possible defensive function remains to be elucidated.     

Allocation of proteolytic activity in the seedling of Cynara cardunculus L. in the initial growth stages

Cynara cardunculus L. seeds were germinated in vitro under environmentally controlled conditions. Seeds showed a 60% germination rate, and three growth stages were established based on the seedling mean relative growth rate (RGR). Root, stem and cotyledons were compared in these stages with respect to the emergence of total proteases and cardosin activity and its allocation in the seedling. In growth stage I (1st-5th post-germinative days), seedlings grew very slowly. Total proteases and cardosins were already active at the onset of seedlings in the stem. Total soluble protein remained constant in cardoon seedlings during stage I, and the content of all free amino acids (aa) but proline (Pro) was equally allocated on the 1st post-germinative day. In growth stage II (5th-10th post-germinative days), seedlings grew intensively and exhibited fully developed cotyledons. A pronounced increase in the content of all free aa up to the middle of growth stage II in both stems and roots was observed. In addition, the allocation of the total proteolytic activity and cardosins followed a gradient from the root to the seedling shoot. However, the whole seedling soluble protein remained constant up to the 7th day in and tended to peak on the 10th post-germinative day, being allocated mainly to the seedling stem. In growth stage III (10th-15th post-germinative days), cardoon seedlings exhibited the lowest mean RGR and the highest R/S growth ratio. An intensive degradation of total soluble protein present in the whole seedling except for cotyledons (ca. 5-fold) was observed. Nevertheless, in growth stage III, both the gradients exhibited by total proteases and cardosins activities between the root and the seedling shoot were enhanced, as were contents of all aa except Pro, exhibiting the highest levels in cotyledons on the 15th post-germinative day.     

盐度对无瓣海桑幼苗的生长和某些生理生态特性的影响

本文研究了盐度(0‰～50‰)对无瓣海桑幼苗生长的影响。盐度对无瓣海桑幼苗长叶数、茎长、植株鲜重、主根长、根系鲜重等方面起抑制作用;随盐度的提高,无瓣海桑幼苗成活率下降;但盐度对无瓣海桑幼苗叶片面积存在一个低盐(0‰～10‰)促进、高盐(15‰～40‰)抑制的过程;盐度对叶绿素含量的影响总趋势是随盐度提高,低盐时叶绿素含量下降,而当盐度超过10‰时上升。因此认为：1)无瓣海桑幼苗在无盐存在下,也可正常生长;2)无瓣海桑具有较高的耐盐能力,在盐度0‰～25‰内可正常生长,超过25‰,其生长受到抑制。     

Ringing induces the accumulation of vegetative storage proteins in poplar bark

Poplar branches were ringed in late spring to determine whether the interruption of the phloem flow could induce the accumulation of vegetative storage proteins (VSPs) in the bark of adult trees. Eight days after ringing, an increased deposition of starch as well as a premature rise in the soluble-protein level occurred in the bark tissues located 1 cm above the ring. Changes in the SDS-PAGE pattern of bark proteins were characterized by the accumulation of three polypeptides (32, 36 and 38 kDa), which exhibited the same molecular weight as VSPs described in poplar bark during winter, cross-reacted to antibodies raised against a poplar VSP, and bound to several lectins in the same way as poplar bark VSPs. These results indicate that during the vegetative period, ringing induces the accumulation of VSPs in the bark of poplar.     

Growth rate,photosynthetic activity,and leaf development of Brazil pine seedlings (Araucaria angustifolia[Bert.] O. Ktze.)

Seedlings of Brazil pine, a large-seeded South American conifer, were grown in a climate chamber to investigate vertical growth pattern and the time course of leaf development. We examined shoot growth, photosynthetic performance and markers of leaf maturation such as contents of soluble sugars and activities of sucrose-phosphate synthase (SPS), neutral invertase (nI) and sucrose synthase (Susy). The daily increment of shoot length showed an optimum curve during the first 70 days after germination. The low growth rate during the first 20 days of development correlated with net CO² emission of the seedling. Analyses of leaf maturation markers in older seedlings revealed low sucrose/hexose ratios and high activities of nI and Susy in the uppermost leaves. Although the SPS/Susy ratio was low in these leaves the extractable SPS activity did not change significantly among leaves of different age. The photosynthetic light compensation points of young leaves were about 2-fold higher than those of mature leaves and their photosynthetic capacity was only 50% as high. Our results indicate that a rapid maturation of leaves of Brazil pine seedlings may reduce the respiratory loss of carbohydrates and that the mobilisation of seed storage compounds supports initial shoot growth under light-limiting conditions which may occur in the forest-grassland succession zone.     

Winners and losers: tropical forest tree seedling survival across a West African forest–savanna transition

Forest encroachment into savanna is occurring at an unprecedented rate across tropical Africa, leading to a loss of valuable savanna habitat. One of the first stages of forest encroachment is the establishment of tree seedlings at the forest–savanna transition. This study examines the demographic bottleneck in the seedlings of five species of tropical forest pioneer trees in a forest–savanna transition zone in West Africa. Five species of tropical pioneer forest tree seedlings were planted in savanna, mixed/transition, and forest vegetation types and grown for 12 months, during which time fire occurred in the area. We examined seedling survival rates, height, and stem diameter before and after fire; and seedling biomass and starch allocation patterns after fire. Seedling survival rates were significantly affected by fire, drought, and vegetation type. Seedlings that preferentially allocated more resources to increasing root and leaf starch (starch storage helps recovery from fire) survived better in savanna environments (frequently burnt), while seedlings that allocated more resources to growth and resource‐capture traits (height, the number of leaves, stem diameter, specific leaf area, specific root length, root‐to‐shoot ratio) survived better in mixed/transition and forest environments. Larger (taller with a greater stem diameter) seedlings survived burning better than smaller seedlings. However, larger seedlings survived better than smaller ones even in the absence of fire. Bombax buonopozense was the forest species that survived best in the savanna environment, likely as a result of increased access to light allowing greater investment in belowground starch storage capacity and therefore a greater ability to cope with fire. Synthesis: Forest pioneer tree species survived best through fire and drought in the savanna compared to the other two vegetation types. This was likely a result of the open‐canopied savanna providing greater access to light, thereby releasing seedlings from light limitation and enabling them to make and store more starch. Fire can be used as a management tool for controlling forest encroachment into savanna as it significantly affects seedling survival. However, if rainfall increases as a result of global change factors, encroachment may be more difficult to control as seedling survival ostensibly increases when the pressure of drought is lifted. We propose B. buonopozense as an indicator species for forest encroachment into savanna in West African forest–savanna transitions.     

Effects of artificial and western spruce budworm (Lepidoptera: Tortricidae) defoliation on growth and biomass allocation of Douglas-fir seedlings

Artificial defoliation has been used commonly to simulate defoliation by insect herbivores in experiments, in spite of the fact that obvious differences exist between clipping foliage and natural defoliation due to insect feeding. We used a greenhouse experiment to compare the effects of artificial and western spruce budworm (Choristoneura occidentalis Freeman) defoliation on the growth and biomass allocation of 3-yr old half-sib seedlings from mature Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco variety glauca] trees that showed phenotypic resistance versus susceptibility to budworm defoliation in the forest. Artificial clipping of buds mimicked the effects of budworm feeding on total seedling biomass when 50% of the terminal buds were damaged. However, artificial defoliation decreased seedling height, relative growth rate of height, and shoot: root ratio more than budworm defoliation, whereas budworm defoliation decreased stem diameter relative growth rate more than artificial defoliation. Half-sib seedling progeny from resistant maternal tree phenotypes had greater height, diameter, biomass, and shoot: root ratio than seedlings from susceptible phenotypes. We concluded that careful artificial defoliation could generally simulate effects of budworm defoliation on total biomass of Douglas-fir seedlings, but that the two defoliation types did not have equal effects on biomass allocation between shoot and root. Further, an inherently higher growth rate and a greater allocation of biomass to shoot versus root are associated with resistance of Douglas-fir trees to western spruce budworm defoliation.     

15科温带树木营养贮藏蛋白质的细胞学研究

利用光学显微镜技术和组织化学方法研究１５科２９种２变种 温带树木中的营养贮藏蛋白质（ＶＳＰｓ）的分布和形态。结果表明,ＶＳＰｓ在树木中的分布分为ＶＳＰｓ丰富、贫乏和缺乏３种类型。同时,ＶＳＰｓ有多种形态,大致可分为蛋白体状、颗粒状和絮状３种,这些形态的ＶＳＰｓ存在于不同的树木中或同一树种的不同细胞中。ＶＳＰｓ的有无、多少及其形态在不同科树木之间及同一科不同属树木之间存在在较大差异,但在同一属树种之     

Architectural analysis of 1-year-old apple seedlings according to main shoot growth and sylleptic branching characteristics

Main shoot and sylleptic shoot growth characteristics were measured during and after the first year of growth of 255 Telamon x Braeburn apple seedlings. Although mean main shoot growth characteristics between branched and non-branched trees were significantly different, many non-branched trees expressed similar main shoot growth to branched trees. The variables describing length, number and position of the sylleptic shoots were used to classify branched trees into architecturally different groups. A continuum from trees with few and short shoots to trees with many long shoots is observed. The release of axillary buds from apical dominance is not under complete control by the apical meristem. Genetic seedling difference at the level of roots presumably plays an important role in sylleptic branching. Genetic variation in terms of number, position, and subsequent elongation of sylleptic shoots is clearly observed.     

Seedling vigour and the early growth of transplanted rice (Oryza sativa)

Previous studies suggest that the positive response of transplanted rice (Oryza sativa L.) to nursery fertiliser application was due to increased seedling vigour or possibly to increased nutrient content. This paper presents results of two glasshouse experiments designed to test the hypothesis that seedling vigour was responsible for the response of transplanted seedlings to nursery treatments. The aim of the present study was to explore the concept of seedling vigour of transplanted rice and to determine what plant attributes conferred vigour on the seedlings. Seedling vigour treatments were established by subjecting seedlings to short-term submergence (0, 1 and 2 days/week) in one experiment and to leaf clipping or root pruning and water stress in another to determine their effect on plant growth after transplanting. Submerging seedlings increased plant height but depressed shoot and root dry matter and root:shoot ratio of the seedling at 28 days after sowing. After transplanting these seedlings, prior submergence depressed shoot dry matter at 40 days. Nursery nutrient application increased plant height, increased root and shoot dry matter, but generally decreased root:shoot ratio. Pruning up to 60% of the roots at transplanting decreased shoot and root dry matter, P concentration in leaves at panicle initiation (PI) and straw dry matter and grain yield at maturity. By contrast, pruning 30% of leaves depressed shoot and root dry matter by 30% at PI, and root dry matter and straw and grain yield by 20% at maturity. The combined effects of leaf clipping and root pruning on shoot, root and straw dry matter were largely additive. It is concluded that the response of rice yield to nursery treatments is largely due to increased seedling vigour and can be effected by a range of nutritional as well as non-nutritional treatments of seedlings that increase seedling dry matter, nutrient content, and nutrient concentration. Impairment of leaf growth and to a lesser extent root growth in the nursery depressed seedling vigour after transplanting. However, rather than increasing stress tolerance, seedling vigour was more beneficial when post transplant growth was not limited by nutrient or water stresses.     

Distribution of assimilate during the flush cycle of growth in Theobroma cacao L.

The growth of the shoot and roots of seedling plants of cocoa (Theobroma cacao L.) under constant glasshouse conditions showed a rhythmic cycle, with the maximum growth stages of each alternating in a regular sequence. When the growth cycle of the shoot was upset by removing all new leaves immediately after unfolding, the roots showed a high constant growth rate during this period, suggesting that normally the rapidly expanding leaves exert an inhibitory influence on the roots. Conversely removal of portions of the root delayed the production of new leaves in the shoot. The level of soluble and starch carbohydrate in the mature leaves, roots and stem declined during the period of expansion of the flush leaves, but accumulated again at the end of the leaf expansion stage. It is likely that this reserve carbohydrate was remobilised and translocated to the flush leaves during their period of expansion. A large proportion of newly formed photoassimilate, as shown by the distribution of ¹⁴C radioactivity from different source leaves, was also translocated to the young leaves during expansion. The large sink created by these leaves may cause photoassimilate and reserve carbohydrate to be diverted from the roots, thereby inhibiting root growth during the stage of leaf expansion. It is suggested that the rhythmic leaf production at the apex may control the growth cycle of the roots.     

Survival and growth of konara oak (Quercus serrata Thunb.) seedlings in an abandoned coppice forest

Survival and growth of konara oak (Quercus serrata) seedlings were examined on the forest floor of a konara oak coppice stand in Mitaka, Tokyo, for 5 yr (1976–1980) after exclusion of human management. Attention was mainly focused on a large cohort derived from a bumper acorn crop in 1975. Seedlings began to branch in the second year, although some did not branch during the whole 5-yr period. Branched seedling showed higher survival and greater weight in 1980 than unbranched seedlings. Many of the branched seedlings had lost an orthotropic leader shoot and spread their branches laterally, suggesting a response for efficient light-capture. As for unbranched seedlings, a size relationship between leaf area and stem length developing every year was dependent on the shoot size. A small shoot gave priority to enlargement of leaf area, whereas a large shoot gave priority to stem elongation. Yearly variations in seedling mortality and stem elongation were related to the amount of precipitation. Both the initial height and leaf area of germinated seedlings were positively correlated with their survival and weight after five years. Five-year survival of seedlings showed a positive correlation with light intensity at the growth site but a negative correlation with the extent of leaf predation. Sprouts of shrub species grew vigorously and became much taller than the oak seedlings in the 5-yr observation period. The characteristics of forest-floor seedlings were discussed in relation to the regeneration of konara oak forests in general.     

Seedling development of the miombo woodland tree Julbernardia globiflora

Abstract. The development of seedlings of the miombo tree (Julbernardia globiflora) was studied for 28 months (December 1987 - April 1990) at a Zambian grassland site from which fire has been excluded for many years. Germination occurred 10–25 days after seed planting and germination rates under laboratory and field conditions did not differ significantly. Seed germinability after one year of storage declined to 38 %. Leaf production occurred between December and April with peaks in January each year. Leaf fall occurred steadily throughout the dry season but leafless seedlings were first observed in August of each year. All seedlings had shed all their leaves by the end of November during the first year while 10% of the seedlings remained leafy throughout the second year. Annual seedling mortality was about 60 % during the first year and declined to 3 6 % during the second year. Survivorship appeared to stabilise at 3 8 % when seedlings were 5 5 - 5 9 weeks old. Every seedling experienced shoot die-back during the first hot dry season (September - November) when open-pan evaporation rates averaged 5–10 mm / day. However, shoot mortality did not necessarily result in plant mortality. Because of recurrent shoot die-back there was little increase in shoot biomass and height at the end of the second and third growing seasons. Seedlings that survived shoot die-back sprouted from roots which showed a steady annual accumulation of biomass. Early shoot die-back in seedlings of Julbernardia globiflora as documented in this study was not causedby fire but most probably by drought and / or nutritional stress.     

结果初期黄冠梨对春施15N-尿素的吸收、分配与利用

以3年生黄冠梨为材料,探讨了早春施用¹⁵N尿素后,树体在萌芽期-新梢缓慢生长期和新梢缓慢生长期-果实成熟期对氮素的吸收、分配与利用特性。结果表明: 梨树在萌芽期-新梢缓慢生长期主要以新梢和叶片等营养器官生长为核心;在新梢缓慢生长期-果实成熟期则以根系等贮藏器官生长为主,果实产量品质形成为辅,且树体尤其是贮藏器官的生物量成倍增加。由于各器官尤其是新梢和叶片生长旺盛、新梢缓慢生长期吸收的标记氮量相对较多,各器官吸收的肥料氮(Ndff)值相对较高;果实成熟期除粗根外各器官的Ndff值均低于新梢缓慢生长期。萌芽期到新梢缓慢生长期吸收的标记氮主要分配在新梢和叶片营养器官中,新梢缓慢生长期到果实成熟期吸收的标记氮则主要分配在贮藏器官中;整个生育期间,植株吸收的标记氮在贮藏器官中分配率最高,营养器官次之,生殖器官中分配率最低。3年生梨树从萌芽期-新梢缓慢生长期、新梢缓慢生长期-果实成熟期吸收的肥料氮分别占当年总吸氮量的31.1%和21.0%,而两个时期内吸收的土壤氮占比分别达68.9%和79.0%。     

广东亚热带森林木本植物幼苗生长特性研究

研究了广东亚热带42种木本植物幼苗的生长及其与物种的生态特性、生活型、种子大小的相互关系.较强光下(H,66.8 μmol m-2s-1)乔木幼苗的茎高和茎生物量显著高于灌木幼苗的相应值,但在较低光下(L,33.7 μmol m-2s-1)两者无显著差异.而阳性植物、耐阴植物和中间型植物之间,茎高和茎生物量无显著差别.乔木幼苗的叶面积和叶生物量比灌木幼苗大,但灌木幼苗的叶片数较乔木幼苗多.大种子种和小种子种幼苗之间,阳性植物、耐阴植物和中间型植物幼苗之间的叶片数和叶面积一般无显著差异.阳性植物幼苗比耐阴植物幼苗侧根数多.乔木幼苗的根生物量和根/茎比显著高于灌木幼苗在较高光下,阳性植物幼苗的根/茎比较耐阴植物幼苗高,但在较低光下无明显差异.45 d幼苗的根生物量与种子重量呈显著的正相关,而90 d幼苗无明显的相关.乔木幼苗个体生物量显著高于灌木幼苗.幼苗相对生长率和叶面积比的大小呈现如下顺序阳性植物＞中间型植物＞耐阴植物,但只有阳性植物和耐阴植物之间有显著差异.阳性植物、中间型植物和耐阴植物幼苗之间的单位叶率无显著差异.     

Effects of large herbivores and fire on the regeneration of Acacia erioloba woodlands in Chobe National Park, Botswana

Acacia erioloba woodlands provide important forage and shade for wildlife in northern Botswana. Mortality of mature trees caused by browsing elephants has been well documented but the lack of regeneration of new trees has received little attention. Annual growth of new shoots and changes in height were measured to determine the influence of elephants and small ungulate browsers, rainfall and fire on the growth and survival of established A. erioloba seedlings from 1995 to 1997 in the Savuti area of Chobe National Park. All above‐ground vegetation was removed from 40% of established seedlings in 1995 and 28% in 1997 by browsing elephants, and the mean height of remaining seedlings decreased from >550 mm to <300 mm. When seedlings browsed by kudu, impala and steenbok but not elephants are considered, mean seedling height increased <50 mm per year, even though mean new shoot growth remaining at the end of the dry season was 100–200 mm. Fires burned portions of the study area in 1993 and 1997, killing above‐ground vegetation, but most established A. erioloba seedlings survived, producing coppice growth from roots. While elephants and fire caused the greatest reduction in established seedling height and number, small browsers suppressed growth, keeping seedlings vulnerable to fire and delaying growth to reproductive maturity.     

Hypocotyl of seedlings of the large-seeded species Araucaria angustifolia: an important underground sink of the seed reserves

Araucaria angustifolia exhibits cryptogeal germination, where the root–hypocotyl axis emerges first and penetrates into the soil. In Araucaria bidwillii, the whole process of transferring reserves from the seed to the seedling takes place before shoot emergence, and there is a major storage of these reserves in the underground hypocotyl, which assumes a tuberous form. In A. angustifolia, the shoot emerges before seed reserves are depleted. Though it does not grow like a tuber, the hypocotyl of A. angustifolia grows thicker than the adjacent taproot during initial growth, and we hypothesize that it may act as a major sink for seed reserves during this stage. The study tests this hypothesis by evaluating changes in the mass of different plant parts during initial growth. Four harvests were conducted during a ~6-month period to compare the dry mass of different fractions (attached seed, seedling, its shoot and root and the hypocotyl) of seedlings growing under darkness and high light. While seed reserves were still being depleted, the hypocotyl mass showed an initial increase and then a reduction. This was more abrupt when light was available. After seed mass had stabilized, the mass of the hypocotyl continued to decrease in the dark-grown seedlings, but showed a second increase in the light-grown ones. Results confirm the hypothesis that the hypocotyl represents a major sink for the seed reserves of A. angustifolia, acting as an underground storage structure for the growing seedling. Its reserves seem to be important for sustaining initial shoot growth and might also act as a storage sink for photosynthates.