Carbon Integration in Plantago aristata (Plantaginaceae): The Reproductive Effects of Defoliation

Horton, Margaret; Lacey, Elizabeth P.

doi:10.2307/2445453

Cited by 5 publications

(7 citation statements)

References 34 publications

(56 reference statements)

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“…Support for the hypothesis that tolerance to defoliation in annuals increases from the vegetative rosette stage to the reproductive stage has previously been obtained in greenhouse experiments with A. thaliana [33] but see [28], Plantago aristata [17], Raphanus sativus [16], Sesbania macrocarpa and S. vesicaria [15], and in a field study of Ipomoea purpurea [13]. In contrast, no evidence of an ontogenetic increase in tolerance to defoliation was observed in a greenhouse experiment with Senecio vulgaris [34], or in a field study of Cucurbita pepo [35].…”

Section: Discussionmentioning

confidence: 69%

“…There is some support for the predictions that leaf damage early in the season is more detrimental than damage late in the season, e.g. [13], [15], [16], and that the components of fitness most affected by herbivory shift along ontogeny in annual plants [17]. However, because responses to herbivory may often be context-dependent [7], [9], [11] and most studies of seasonal changes in tolerance to leaf herbivory have been conducted in the greenhouse rather than in the field, e.g.…”

Section: Introductionmentioning

confidence: 89%

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Magnitude and Timing of Leaf Damage Affect Seed Production in a Natural Population of Arabidopsis thaliana (Brassicaceae)

Akiyama

Ågren

2012

PLoS ONE

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BackgroundThe effect of herbivory on plant fitness varies widely. Understanding the causes of this variation is of considerable interest because of its implications for plant population dynamics and trait evolution. We experimentally defoliated the annual herb Arabidopsis thaliana in a natural population in Sweden to test the hypotheses that (a) plant fitness decreases with increasing damage, (b) tolerance to defoliation is lower before flowering than during flowering, and (c) defoliation before flowering reduces number of seeds more strongly than defoliation during flowering, but the opposite is true for effects on seed size.Methodology/Principal FindingsIn a first experiment, between 0 and 75% of the leaf area was removed in May from plants that flowered or were about to start flowering. In a second experiment, 0, 25%, or 50% of the leaf area was removed from plants on one of two occasions, in mid April when plants were either in the vegetative rosette or bolting stage, or in mid May when plants were flowering. In the first experiment, seed production was negatively related to leaf area removed, and at the highest damage level, also mean seed size was reduced. In the second experiment, removal of 50% of the leaf area reduced seed production by 60% among plants defoliated early in the season at the vegetative rosettes, and by 22% among plants defoliated early in the season at the bolting stage, but did not reduce seed output of plants defoliated one month later. No seasonal shift in the effect of defoliation on seed size was detected.Conclusions/SignificanceThe results show that leaf damage may reduce the fitness of A. thaliana, and suggest that in this population leaf herbivores feeding on plants before flowering should exert stronger selection on defence traits than those feeding on plants during flowering, given similar damage levels.

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Section: Discussionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 89%

Magnitude and Timing of Leaf Damage Affect Seed Production in a Natural Population of Arabidopsis thaliana (Brassicaceae)

Akiyama

Ågren

2012

PLoS ONE

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“…Leaf removal moderately aected the number of seeds produced by early¯owers, but again these decreases in both fruit and seed set could not be ascribed to changes in pollination levels. In general, seed output in A. aurea seems to be well buered against damage to leaves close to the in¯orescence (Aizen and Raaele 1996), which contrasts with ®ndings for other species in which the removal of even small portions of leaves subtending in¯orescences may lead to strong eects on reproduction (Marquis 1988(Marquis , 1992Horton and Lacey 1994; but see Obeso and Grubb 1993). It might well be that rhizomes, specialized starch-storing roots, or even associated vegetative shoots (Bayer 1987) are important sources of carbohydrates and nutrients for reproduction in A. aurea in addition to the resources provided locally by the¯owering shoots themselves.…”

Section: Discussionmentioning

confidence: 85%

Early reproductive failure increases nectar production and pollination success of late flowers in south Andean Alstroemeria aurea

Ladio¹,

Aizen²

1999

Oecologia

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Fertile ramets of bumblebee-pollinated Alstroemeria aurea, a clonal perennial native to the temperate forests of the southern Andes, produce single terminal inflorescences that may bear two or more temporally non-overlapping whorls of flowers. While fruit set is commonly high (>80%) among early-opening flowers, it is usually low (<20%) among late-opening flowers within ramets. Using flowering ramets with two whorls of flowers, we examined experimentally the following related hypotheses. First, late flowers act as a reserve of ovaries, increasing their likelihood of setting seed when early fruits abort due to either pollen or resource limitation. Second, where early fruit abortion has occurred, plants may actively ensure pollination of late flowers by increasing their attractants and rewards. In a natural population, we simulated (1) lack of pollen deposition in early flowers, by excising their stigmas just before receptivity, and (2) resource limitation, by removing all the leaves from an experimental flowering ramet. Treatments were applied to individual ramets according to a 2 × 2 factorial design. We found that when early flowers failed to set fruit due to stigma excision, nectar secretion and particularly pollen receipt strongly increased in late flowers. Higher pollen deposition contributed significantly to the observed five-fold increase in seed output of late flowers. Fruit and seed set from early flowers were more negatively affected by defoliation than that from late flowers. Defoliation did not interfere with a ramet's capacity to increase late reproductive output when early reproduction failed. These results support the assertion that late flowers act as a reserve of ovaries helping a plant to cope with an unpredictable environment. These results also suggest that plants may actively increase pollinator visitation by opportunistically increasing flower rewards.

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“…In one (Plantago virginica), the reproductive metamers are integrated by ~4C-assimilate transport, whereas in the other (P. aristata), the reproductive metamers appear to be quite independent with respect to carbon assimilated by neighbouring metamers, and so can be regarded as IPUs (Lacey & Marshall 1992). The latter conclusion is further supported by the response of individual metamers of P. aristata to defoliation, following which their reproductive performance is significantly reduced, thereby indicating the inability of the spike to be supplied with a significant amount of assimilate from adjacent metamers to buffer the local shortfall (Horton & Lacey 1994). It would therefore appear that adjacent reproductive metamers of this species are not connected by functional phloem, but this needs to be verified by anatomical investigation.…”

Section: Shoots and Branchesmentioning

confidence: 90%

Sectoriality and physiological organisation in herbaceous plants: an overview

Marshall

1996

Vegetatio

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The physiological organisation of plants is considered in relation to the carbon economy of plant parts. Although assimilate is partitioned according to the relative strength of sinks, in many species there is also a very close relationship between partitioning and shoot phyllotaxy, giving rise to sectorial patterns of allocation whereby only certain sinks are supported by any source leaf. Essentially these sinks are in the same orthostichy as the source leaf. This constraint of the vascular architecture on assimilate distribution to developing sinks such as leaves, flowers and fruits is not always absolute, as following the loss of their principal source leaves these sinks can in many cases be supplied with assimilate by other leaves via new inter-orthostichy pathways. The supply of assimilate to major sinks such as developing fruits becomes more and more localised with time so that a fruit in an axillary position becomes largely supported by its subtending leaf; the reproductive node -a metamer -can thus be regarded as a relatively autonomous unit of the plant (an IPU). Similarly, once established after a developmental phase of assimilate import, tiller ramets and branches in unitary plants tend to become physiologically autonomous modules. However, the functional autonomy of tillers is reversed following defoliation or shading as they are then sustained by the import of assimilate, subject to its availability, from unaffected tillers. Consequently the plant becomes physiologically integrated by the flow of assimilate from one part to another. The mainly autonomous ramets of many stoloniferous and rhizomatous species display a similar pattern of physiological integration in response to source manipulation, but in some species the ramets appear to maintain their independent functioning as a normal feature of the carbon allocation within the clone. In other clonal species, as the clone develops and becomes more structurally complex, vascular constraints start to restrict the movement of resources, and the clone becomes composed of a number of semi-autonomous IPUs. In unitary plants branches appear to remain very physiologically isolated in terms of their carbon economy once they become established, irrespective of a range of source-sink manipulations.These different patterns of physiological integration and organisation are discussed in relation to different strategies of assimilate utilisation and conservation.

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Carbon Integration in Plantago aristata (Plantaginaceae): The Reproductive Effects of Defoliation

Cited by 5 publications

References 34 publications

Magnitude and Timing of Leaf Damage Affect Seed Production in a Natural Population of Arabidopsis thaliana (Brassicaceae)

Magnitude and Timing of Leaf Damage Affect Seed Production in a Natural Population of Arabidopsis thaliana (Brassicaceae)

Early reproductive failure increases nectar production and pollination success of late flowers in south Andean Alstroemeria aurea

Sectoriality and physiological organisation in herbaceous plants: an overview

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