Continuous basal sprouting from a lignotuber:Arbutus unedo L. andErica arborea L., as woody Mediterranean examples

Summary The two dominant species of the Corsican mattoral,Arbutus unedo L. andErica arborea L., can produce abundant sprouts from the lignotuber not only immediately after fire but also more or less continuously in the absence of major disturbance. The lignotuber appears to be more important during the early stages of development; the result is an increase in the number of sprouts during the 25 years following the establishment of the individuals. Later the lignotuber seems to lose the ability to ensure the development of new basal sprouts. A hypothesis is that the presence of a lignotuber is related to the growth form.Arbutus unedo andErica arborea show behaviour intermediate between acrotony and basitony, as the shoots show acrotony, and continuous sprouting is characteristic of basitonic species. The fact that sprouting from the lignotuber is not necessarily a result of fire suggests that the relation between fire and vegetation in the Mediterranean region should be reconsidered.     

Root starch storage and allocation patterns in seeder and resprouter seedlings of two Cape Erica (Ericaceae) species

Post-fire sprouting of dormant buds in resprouter plants is facilitated by stored carbohydrate reserves, with starch being the critical reserve. Starch is mainly stored in xylem parenchyma ray tissue of woody underground organs, such as burls, lignotubers, and roots. We carried out a comparative analysis of the pattern of starch storage and the proportion of parenchymatic ray tissue in the upper root or cotyledonary region of seedlings from seeder and resprouter forms within two Cape Erica (Ericaceae) species: E. coccinea L. and E. calycina L., which were raised in the greenhouse under controlled irrigation. We also explored the root-to-shoot allocation patterns of seeder and resprouter seedlings in these two species. Resprouter seedlings of both species showed higher relative amounts of upper-root starch and upper-root storage tissue as well as a higher root-to-shoot allocation than their seeder counterparts. Pronounced swelling of the upper root region suggests ontogenetic development of a lignotuber in the resprouter forms of the two Erica species. The distinct allocation of starch in roots seems to be genetically determined and would account for the apparent differences in the root-to-shoot allocation patterns between both regeneration forms from the early seedling stage.     

No allocation trade-offs between flowering and sproutingin the lignotuberous,Mediterranean shrub Erica australis

Trade-offs between allocation to sexual or vegetative regeneration capacity are well established as a driving force in the life history patterns of plants in fire-prone environments. However, it is not known whether such trade-offs exist in plants which after aboveground removing disturbances, such as fire, may regenerate by sexual (seeding) or asexual (sprouting) mechanisms. We evaluated whether in the fire-recruiting resprouter Erica australis, which after fire can regenerate by seedling establishment or resprouting, a larger investment in flowers and seeds prior to being disturbed by clipping its aboveground parts would decrease subsequent sprouting, that is, its vegetative regeneration capacity. We analysed the relationships between flower and seed production and the ensuing production and growth of sprouts of six plants from thirteen different sites in central-western Spain. We found no significant relationships between measures of sexual reproductive effort and resprout production and growth 6 months after clipping the aboveground parts of the plants. No evidence of trade-offs between sexual and asexual efforts was found. Furthermore, no significant relationship was found between lignotuber total non-structural carbohydrates and sexual reproductive effort. In addition, 2 years after the disturbance, resprout biomass was positively and significantly correlated with sexual reproductive effort prior to the disturbance. This indicates that growth of resprouts was higher at the sites where plants made a greater reproductive effort. The sites that were more favourable to producing flowers and seeds could also be more favourable to resprouting.     

Dynamics of resprouting in the lignotuberous shrub Banksia oblongifolia

The resprouting response of different sized Banksia oblongifolia lignotubers (genets) was followed in two field experiments. In the first, the density and speed of resprouting, and the growth in length of the leading shoot from each lignotuber in response to fire and to the time elapsed since the last fire was monitored for 18 months after fire and clipping treatments. In the second, sizes of bud banks were estimated by repeatedly clipping new shoots from individual lignotubers. Density of resprouting (shoots dm^?2 lignotuber) decreased with increasing lignotuber size, and the length of the leading shoot increased. The direct effect of fire was to reduce shoot density by about 75%. The speed of resprouting (time taken by a cohort of shoots to reach 50% of their peak density) was similar after fire and clipping, but leading shoots grew significantly longer after fire. The elapsed time since lignotubers were last burnt did not influence their density of resprouting, but it did influence the speed of resprouting. Shoots from clipped lignotubers that had burnt 3 years earlier took about 90 days to each 50% of their peak density while shoots on lignotubers last burnt 5 and 17 years earlier took about 40 days. Death of shoots was unrelated to crowding in any stand. More lignotubers from the oldest unburnt stand were grazed by herbivores. The number of buds converted into shoots after successive clippings was surprisingly small; for most lignotubers this reserve was less than three times the size of their standing crop of shoots. In general, the smaller lignotubers carried a higher proportion of dormant buds in relation to their standing crop of shoots. About 30% of buds remained dormant after the first clipping and about 10% after the second and third clippings. Evidence suggests that buds are replaced within 6 months of fire. No lignotubers survived four clippings over 15 months.     

Activities of starch hydrolytic enzymes and starch mobilization in roots of <Emphasis Type="Italic">Caragana korshinskii</Emphasis> following above-ground partial shoot removal

In many resprouting plants, carbohydrates are stored as starch in roots and will be mobilized to support above-ground tissue regrowth after shoot damage. Our objective was to determine how activities of starch hydrolytic enzymes change damage-induced starch mobilization in Caragana korshinskii roots after above-ground tissue loss. Zero percent (control), 30% (30% RSL), 60% (60% RSL) of main shoot length, and 25% (25% RSN), 50% (50% RSN), and 100% (100% RSN) of main shoot number were removed. Compared with control plants, clipping accelerated the reduction of starch in the roots, increased sucrose flux per flower per hour and nectar production per flower per day in 30% RSL, 60% RSL, 25% RSN, and 50% RSN treatments, and improved vegetative growth in 100% RSN treatment. All treatments had similar total nonstructural carbohydrate (TNC) concentrations in leaves, shoots, and stems with the exception of 100% RSN with higher TNC concentration in shoots. Both α-, and β-amylase activities were enhanced by clipping, the former being more strongly correlated with starch degradation in the roots than the latter. The other two possible starch-breaking enzymes, α-glucosidase, and starch phosphorylase showed no significant differences in the activities between treatments. The results suggest that starch degradation in the roots of C. korshinskii was regulated by α-amylase activity and more mobilized starch was used to support vegetative growth in 100% RSN treatment and support sexual reproduction followed by other clipping treatments.     

Resprouting vigour of two mediterranean shrub species after experimental fire treatments

Experimental fire treatments were carried out by applying a propane torch flame to individual stumps ofArbutus unedo andErica arborea, two dominant ericaceous shrubs living in relatively moist maquis of the western Mediterranean Basin. No mortality was observed in either species. Individual plant size, measured as the individual stump area, was the most important factor determining both number and biomass of resprouts for all fire treatments. The number of resprouts at 3 months was less at the higher temperature, but no difference could not be detected at 18 months. Duration of flame application had no effect on resprouting success. This effect was not statistically significant 18 months after treatments were applied. Biomass of resprouts was not clearly affected by different fire treatments either 3 months or 18 months after the start of the resprouting process.     

Phosphorus accumulation by lignotubers of jarrah (Eucalyptus marginata Donn ex Sm.) seedlings grown in a range of soils

Summary Jarrah seedlings were grown in six virgin Western Australian soils for up to 27 months. Lignotubers were produced in all soils and formed 10–16% of plant dry weight. The phosphorus concentration in the lignotuber (250–800 g g^–1) was nearly twice that in the stem and roots. The lignotuber contained 10–30% of total plant phosphorus and like the leaves was a sink for phosphorus. In one lateritic soil the phosphorus concentrations of lignotuber and stem barks were similar. However, in the same plants the concentration of phosphorus in the lignotuber wood was five times the phosphorus concentration in stem wood. Hence both lignotuber bark and sap wood in young jarrah seedlings are storage sites for phosphorus. X-ray probe analysis showed that wood phosphorus was associated with the ray parenchyma. Unlike phosphorus, nitrogen did not accumulate in the lignotuber and the concentrations of nitrogen were similar for roots, lignotubers and stems.     

Non-structural carbohydrate accumulation and use in an understorey rain-forest shrub and relevance for the impact of leaf herbivory

1. Piper arieianum, an evergreen, understorey shrub of lowland moist forests of Central and South America, exhibits marked seasonal variation in reproductive activity even though climatic variation is low at the study site. Despite a lack of climatic seasonality, previous experimental leaf removal suggested that carbohydrate accumulation is seasonal, occurring prior to flowering.
2. We first tested the hypothesis that carbohydrates necessary for reproduction are accumulated prior to flowering, rather than during or after. By measuring non-structural carbohydrate production in the form of glucose and starch we found that the concentration of these reserves is greatest 1–3months before flowering, decreasing by 50% during peak fruit maturation.
3. The hypothesis that reproduction was the cause of this decrease in carbohydrate reserves was then tested by comparing reserves in plants that were prevented from flowering with those that flowered and produced fruit naturally. As predicted, reserves declined more in flowering than in non-flowering plants. A smaller decline in reserves of non-flowering plants was accompanied by greater stem and leaf production, suggesting that stored carbohydrates are also required for growth.
4. Because concentrations of non-structural carbohydrates were similar in roots, stems and leaves, and because the greatest amount of plant biomass is in stems for plants of a range of sizes, stems appear to be the main storage site of carbohydrate reserves in this plant species.
5. These results, together with previous studies, demonstrate that the impact of leaf herbivory on seed production in P. arieianum depends on the timing of that herbivory relative to the accumulation and use of non-structural carbohydrates.     

Resprouting of Erica multiflora after experimental fire treatments

Abstract. The effect of fire intensity - both temperature and duration - on the resprouting pattern of the evergreen Mediterranean shrub Erica multiflora in relation to plant size, was experimentally investigated by subjecting plants to the flame of a propane torch, and observing mortality and resprouting after 5 and 20 months. Pre-treatment plant size was not important in determining post-fire plant survival, but it did influence the resprouting vigour, increasingly so with time. High temperatures induced higher mortality rates within populations, but duration of fire did not effect mortality. Biomass of resprouts was lower following more intense fire treatments, but this effect progressively disappeared over time, except in plants subjected to the most intense fire treatment. This is probably because of the increasing importance of the below-ground organs for the regeneration of the above-ground biomass. Some of the plants which were clipped but not exposed to fire also died 20 months after treatment. The effect of clipping onmortality andresprout-ing response, estimated as biomass of resprouts, was not significantly different from the effect induced by either low or medium temperature treatments, but was significantly different when compared with the effect of high-temperature treatments. Field observations show that the establishment of seedlings of E. multiflora is rare both after fire and between fires. Thus, our data support the idea that both a single fire or clipping can diminish the population size of a resprouting species. We conclude that fire may have a stochastic effect on E. multiflora populations, due to the variation in fire intensity existing within a single burning stand.     

Resistance of three co-occurring resprouter Erica species to highly frequent disturbance

The resistance to experimental, highly frequent disturbance has been analysed in three congeneric, strong-resprouter species (Erica australis, E. scoparia and E. arborea) that co-occur in heath-dominated communities of the northern side of the Strait of Gibraltar, southern Spain. To do so, mature individuals of the three species from a long undisturbed location were clipped at the ground level every sixth month during two years. The relationship between the resprouted biomass dry weight (as indicative of the resprouting vigour) and the upper surface area of the lignotuber along the experiment was established separately for each species at each clipping event by means of linear regressions analysis. The resprouting vigour of the three species was compared by means of independent one-way ANOVAs within each clipping event. Resprouting vigour decreased after recurrent clippings in the three species. Nevertheless, significant differences between species in this loss of resprouting vigour were detected, being E. scoparia the most resistant to the experimental, highly frequent clipping. It is concluded that experimental levels of recurrent disturbance may help to find out differences in resilience within similar (taxonomically, morfologically and/or ecologically), strong-resprouter plant species. Considering the history of forestry management in the nothern side of the Strait of Gibraltar, differences in this regard between the three Erica species may contribute to explain their somewhat segregated ecological distribution in this region.     

Lignotuber size of Erica australis and its relationship with soil resources

Abstract. It has been proposed that resprouting after a disturbance would be favoured under conditions of low soil resource availability. In lignotuberous plants of Mediterranean‐type areas, successful resprouting after disturbances such as fire depends on the size of the lignotuber, but little is known about the role of soil resources in determining the relative size of this organ. In this work we tested whether the relative size of the lignotuber in the resprouting shrub Erica australis is related to the availability of soil resources. At each of 13 different sites in Spain, 10 plants were chosen and the sizes of their various parts (above‐ and below‐ground) measured. Additionally, at each site we evaluated soil fertility, foliar N and P concentrations and plant water potential in the middle of the summer. The relationships between lignotuber dimensions and the various plant parts were assessed. In all cases, significant differences between sites were found indicating consistent differences in lignotuber size across the range of plant sizes. This was particularly the case when lignotuber dimensions were expressed as a function of foliar biomass. Lignotuber dimensions relative to foliar biomass were positively correlated with soil pH and negatively with plant water potentials in midsummer. There were, however, no clear relationships between lignotuber relative dimensions and soil N and P contents or other measures of site productivity. In summary, lignotubers were not smaller at more productive sites, in fact they were relatively larger at sites where soils were less acidic, but where plant water conditions were less favourable. These findings contradict predictions made based on current theory on the role of soil fertility allocation to resprouting.     

Resprouting in the Mediterranean‐type shrub Erica australis afffected by soil resource availability

Abstract. Soil resource availability may affect plant regeneration by resprouting in disturbed environments directly, by affecting plant growth rates, or indirectly by determining allocation to storage in the resprouting organs. Allocation to storage may be higher in stressful, low resource‐supply soils, but under such conditions plant growth rates may be lower. These factors could act in opposite directions leading to poorly known effects on resprouting. This paper analyses the role played by soil resources in the production and growth of resprouts after removal of above‐ground plant tissues in the Mediterranean shrub Erica australis. At 13 sites, differing in substrate, we cut the base of the stems of six plants of E. australis and allowed them to resprout and grow for two years. Soils were chemically analysed and plant water potential measured during the summer at all sites to characterize soil resource availability. We used stepwise regression analysis to determine the relationships between the resprouting response [mean site values of the number of resprouts (RN), maximum length (RML) and biomass (RB)] and soil nutrient content and plant water potential at each site. During the first two years of resprouting there were statistically significant differences among sites in the variables characterizing the resprouting response. RML was always different among sites and had little relationship with lignotuber area. RN was less different among sites and was always positively correlated with lignotuber area. RB was different among sites after the two years of growth. During the first months of resprouting, RN and RML were highly and positively related to the water status of the plant during summer. At later dates soil fertility variables came into play, explaining significant amounts of variance of the resprouting variables. Soil extractable cations content was the main variable accounting for RML and RB. Our results indicate that resprout growth of E. australis is positively affected by high water availability at the beginning of the resprouting response and negatively so by high soil extractable cation content at later periods. Some of these factors had previously shown to be related, with an opposite sign, to the development of a relatively larger lignotuber. Indeed, RML and RB measured in the second year of resprouting were significantly and negatively correlated with some indices of biomass allocation to the lignotuber at each site. This indicates that sites favouring allocation to the resprouting organ may not favour resprout growth.     

Enhancement of photosynthesis in post-disturbance resprouts of two co-occurring Mediterranean <Emphasis Type="Italic">Erica</Emphasis> species

The higher growth rates of resprouting shoots compared with those of mature plants in resprouter woody species are supported by higher rates of photosynthesis and transpiration. In this contribution we hypothesize that species with higher resprouting vigour will show a larger enhancement of photosynthesis in resprouting shoots. We test this hypothesis by comparing gas exchange and leaf parameters between resprouting and mature plants in Erica scoparia and E. australis. These two Erica species co-occur in Mediterranean heathlands of the Strait of Gibraltar. Erica scoparia has a higher rate of post-disturbance starch recovery than E. australis, which makes it more resistant to recurrent disturbance. We tested the hypothesis that enhancement of photosynthesis and water use characteristics of resprouting shoots compared with mature plants should be more pronounced in E. scoparia. In both species, resprouts had higher efficiency in the use of light and higher maximum net photosynthesis than mature shoots. However, contrary to expectations, differences in the photosynthetic performance between resprouts and mature plant shoots were larger in E. australis. Higher root to shoot ratios in resprouting E. australis plants, determined by their slower above-ground recovery, together with stronger demand from carbon sinks might explain this result.     

Effects of Water and Nutrient Availability on Water Relations, Gas Exchange and Growth Rate of Mature Plants and Resprouts of Arbutus unedo L.

This study examines the effects of water supply and nutritionon the water status, gas exchange and growth of mature plantsand resprouts of Arbutus unedo, a Mediterranean evergreen shrubadapted to drought and poor nutrition. Mature plants of A. unedorespond to irrigation with increased leaf water potential duringsummer drought, but they show a very conservative use of waterand they do not increase leaf conductance. There is also a verysmall increase in net photosynthesis and growth, which doesnot significantly increase productivity. Resprouts of A. unedo increase water potential, leaf conductance,transpiration rate, net photosynthesis and growth rate in responseto watering, showing a less conservative use of water than matureplants. Increased growth rates, both in mature plants and resprouts,are likely to be due to the higher cell turgor caused by improvedleaf water potential, rather than to increased photosynthesis. The only effect of nutrient addition on mature plants is anincrease in leaf nutrient content, and other aspects of thephysiology and growth of resprouts were unaffected. We thereforeconclude that water is a more limiting factor than nutrientsfor mature plants and resprouts of A. unedo growing in the studyarea. These results support previous data which indicate thathigher growth rates in resprouts than in mature plants of A.unedo are mainly the result of a higher water availability.Copyright1994, 1999 Academic Press Arbutus unedo L., strawberry tree, resprouts, water stress, nutrient availability, water relations, gas exchange, growth rate, regeneration     

Costs of reproduction in circumpolar <Emphasis Type="Italic">Parnassia palustris</Emphasis> L. in light of global warming

In frequently burnt savannas, saplings face the formidable challenge of both recovering from, and eventually growing tall enough to escape from, frequent fire damage. The aim of this study was to explore how saplings allocate carbon to achieve these ends through carbon partitioning, storage and remobilization. Lignotuber total non-structural carbohydrate (TNC) concentrations and δ¹³C values of Acacia karroo (Fabaceae; Mimosoideae) were determined in plants from two different juvenile stages. These were one year after a fire when the plant consisted of numerous leafy shoots or coppices (“coppicing” stage), and three years after a fire when the plant consisted of one pole-like stem (“Gulliver” stage). Gulliver lignotubers were found to have significantly larger TNC pools (150 g vs. 97 g) and larger TNC concentrations (33% vs. 24%, w/w) than coppice lignotubers showing that post-coppice Gullivers recharged TNC in the lignotuber. δ¹³C values from the stems of plants in the Gulliver stage were significantly enriched (>1‰) in ¹³C compared to both coppicing (P < 0.01) and adult (P < 0.05) plants. Changes in both the amount of stored carbon and in the δ¹³C values indicated dependence on stored carbon reserves, and partially heterotrophic growth for initial resprouting. The plants appeared to use both current photosynthate and stored carbon reserves for growth of the Gulliver stem. The use of stored carbon is hypothesized to promote fast stem growth rates to a height where saplings escape fire injury.     

Effect of nutrition on the distribution of potassium and phosphorus inCucurbita pepo L.

In young pumpkin plants, the phosphorus was found not to be affected substantially by potassium deficiency whereas the deficiency of calcium has marked effects. Potassium distribution is not affected substantially by either phosphorus or calcium deficiency. In short-term experiments, the presence of calcium affects markedly the total uptake of potassium but the potassium distribution remains unaltered. The stimulation of potassium uptake is far more pronounced in plants pre-cultivated in a complete nutrient solution than in those pre-cultivated in a calcium-deficient one; this is apparently due to profound metabolic changes taking place in plants grown without calcium. The reserves of phosphorus and potassium stored in the cotyledons are easily mobilized and translocated so that they can be used for growth in early stages of development; the appearance of pathological symptoms of phosphorus or potassium deficiency is thus prevented.     

Cassava Response to Water Deficit in Deep Pots: Root and Shoot Growth, ABA, and Carbohydrate Reserves in Stems, Leaves and Storage Roots

Cassava (Manihot esculenta, Crantz) is an important staple crop for tropical climates worldwide, including drought-prone environments where it is valued for its reliable yield. The extent to which stress tolerance involves regulation of growth and carbon balance aided by remobilization of carbohydrate from various plant parts was investigated. Plants were grown in 1-meter high pots to permit observation of deep rooting while they were subjected to four soil water regimes over a 30-d period. Transpiration declined abruptly in conjunction with leaf ABA accumulation and severe leaf abscission. In water stressed plants, growth of all plant parts decreased substantially; however, a basal rate of leaf growth continued to provide some new leaves, and although growth of fibrous lateral roots was reduced, main root elongation to deeper regions was only modestly decreased by stress. In leaf blades and petioles, sugars were the predominant form of nonstructural carbohydrate and about one third was in starch; these reserves were depleted rapidly during stress. In contrast, stems and storage roots maintained relatively high starch concentrations and contents per organ until final harvest. Stems gradually lost starch and had sufficient reserves to serve as a prolonged source of remobilized carbohydrate during stress. The amount of starch stored in stems represented about 35 % of the reserve carbohydrate in the plant at the onset of water stress (T₀), and 6 % of total plant dry mass. We suggest that this pool of carbohydrate reserves is important in sustaining meristems, growing organs, and respiring organs during a prolonged stress and providing reserves for regrowth upon resumed rainfall.     

The importance of nitrogen and carbohydrate storage for plant growth of the alpine herb Veratrum album

We examined whether nitrogen (N) and carbohydrates reserves allow Veratrum album, an alpine forb, to start spring growth earlier than the neighbouring vegetation and to survive unpredictable disturbances resulting in loss of above-ground biomass. * Seasonal dynamics of plant reserves, soil N availability and vegetation growth were monitored. Veratrum album shoots were experimentally removed when carbohydrate reserves were at a seasonal minimum and the subsequent changes in biomass and reserves were compared with those in control plants. Reserves did not give V. album a competitive advantage in spring; however, they did function as a buffer against the impact of calamities. Shoot removal resulted in significantly lower root dry weight, higher N concentration in rhizome and roots and lower starch concentrations in rhizome and roots but no plant mortality was observed. Veratrum album used stored N reserves to supplement N uptake and establish high leaf N concentrations, which facilitated a rapid refilling of depleted carbohydrate reserves. The primary function of N reserves appears to be to allow V. album to complete the growing cycle in as short a period as possible, thus minimizing exposure to above-ground risks.     

Comparative genet survival after fire in woody Mediterranean species

Summary Using data from three fires in northeastern Spain, we tested a condition necessary to support the idea that fire has been a factor in the evolution of the resprouting habit: populations of all resprouting species within a community should show high levels of genet survival after fires and show a low coefficient of variation. Species with high mean survival values were:Quercus ilex L.,Phillyrea latifolia L., andViburnum tinus L., with 88, 86 and 83% survival respectively; these groups had resprouts emerging from rootcrowns. Then followedArbutus unedo L. (75%),Pistacia lentiscus L. (73%),Erica arborea L. (77%),Erica multiflora L. (57%) andJuniperus oxycedrus L. (55%). This last group had resprouts from lignotubers or burls. These two groups also differed in the variability around the mean: the first showed a lower coefficient of variation, 6–12, and the second ranged from 19 to 26. Slope exposure had no significant influence on the process of resprouting, but soil depth did, with precipitation as a covariate. In the shallow soil category, the difference in genet survival between southern and northern exposures was 14% (71% vs. 57%); while the difference in the deep soil category was low, 5% (87% vs. 82%). There was no significant interaction. The component of variance for soils was larger than that for species-specific effects; substantial overlap of the within-species variance indicated that species responded as if they were a single hypothetical population, in which most of the variation in chances of survival was due to the soil conditions. The possession of the resprouting habit did not ensure a high performance. Hence, we find weak support for fire as a factor in the evolution of the resprouting habit.     

Accumulation of non-utilizable starch in laticifers of Euphorbia heterophylla and E. myrsinites

Starch biosynthesis and degradation was studied in seedlings and mature plants of Euphorbia heterophylla L. and E. myrsinites L. Mature embryos, which lack starch grains in the non-articulated laticifers, develop into seedlings that accumulate starch rapidly when grown either in the light or the dark. Starch accumulation in laticifers of dark-grown seedlings was ca. 47 and 43% of total starch in light-grown controls in E. heterophylla and E. myrsinites, respectively. In light-grown seedlings, starch was present in laticifers as well as parenchyma of stems and leaves, whereas in dark-grown seedlings starch synthesis was almost exclusively limited to laticifers. In 7-month-old plants placed into total darkness, the starch in chyma was depleted within 6 d, whereas starch in laticifers was not mobilized. The starch content of latex in plants during development of floral primordia, flowering, and subsequent fruit formation remained rather constant. The results indicate that laticifers in seedlings divert embryonal storage reserves to synthesize starch even under stress conditions (darkness) in contrast to other cells, and that starch accumulated in laticifers does not serve as a metabolic reserve. The laticifer in Euphorbia functions in the accumulation and storage of secondary metabolites yet retains the capacity to produce, but not utilize starch, a primary metabolite.