Plant Organ Size Research Articles

Plant organ size control: AINTEGUMENTA regulates growth and cell numbers during organogenesis.

The control of cell proliferation during organogenesis plays an important role in initiation, growth, and acquisition of the intrinsic size of organs in higher plants. To understand the developmental mechanism that controls intrinsic organ size by regulating the number and extent of cell division during organogenesis, we examined the function of the Arabidopsis regulatory gene AINTEGUMENATA (ANT). Previous observations revealed that ANT regulates cell division in integuments during ovule development and is necessary for floral organ growth. Here we show that ANT controls plant organ cell number and organ size throughout shoot development. Loss of ANT function reduces the size of all lateral shoot organs by decreasing cell number. Conversely, gain of ANT function, via ectopic expression of a 35S::ANT transgene, enlarges embryonic and all shoot organs without altering superficial morphology by increasing cell number in both Arabidopsis and tobacco plants. This hyperplasia results from an extended period of cell proliferation and organ growth. Furthermore, cells ectopically expressing ANT in fully differentiated organs exhibit neoplastic activity by producing calli and adventitious roots and shoots. Based on these results, we propose that ANT regulates cell proliferation and organ growth by maintaining the meristematic competence of cells during organogenesis.

Plant organ size control: Aintegumenta regulates growth and cell numbers during, organogenesis: Mizukami Y, Fischer RL: Proc Natl Acad Sci USA 2000, 97:942–947

Plant organ size control: Aintegumenta regulates growth and cell numbers during, organogenesis: Mizukami Y, Fischer RL: Proc Natl Acad Sci USA 2000, 97:942–947

A morphometric analysis of the Cimicifuga foetida L. complex (Ranunculaceae)

Plants referred to the collective ‘species’Cimicifuga foetida L. occur in four main disjunct areas of Eurasia; (1) Siberia and northern Mongolia; (2) central and western China; (3) Kashmir and western Tibet and (4) middle Europe. Taxonomic limits within this collective group have been very ill-defined, with some authors recognizing only a single variable species comprising variously delimited varieties, and others recognizing a number of separate geographically or morphologically circumscribed species. Our examination of 17 morphometric variables, using Analysis of Variance and Canonical Discriminant Analysis, reveals a number of clear differences in shape and size of plant organs between the four main geographic areas. These morphometric differences, furthermore, correlate well with differences in other, more qualitative, features. We thus recognize four geographically delimited species: C. europaea Schipcz. in Europe, C. foetida L. in Siberia and Mongolia, C. kashmiriana J. Compt. & Hedd. sp. nov. in Kashmir and C. mairei H. Levl, in China. Two varieties, C. foetida var. racemosa Regel and C. mairei var. foliolosa (P.K. Hsiao) J. Compt. & Hedd., are also recognized. Keys and brief descriptions are provided for all the taxa, and the distribution of each species is mapped.

A morphometric analysis of the Cimicifuga foetidaL. complex (Ranunculaceae)

Plants referred to the collective ‘species’ Cimicifuga foetidaL. occur in four main disjunct areas of Eurasia; (1) Siberia and northern Mongolia; (2) central and western China; (3) Kashmir and western Tibet and (4) middle Europe. Taxonomic limits within this collective group have been very ill-defined, with some authors recognizing only a single variable species comprising variously delimited varieties, and others recognizing a number of separate geographically or morphologically circumscribed species. Our examination of 17 morphometric variables, using Analysis of Variance and Canonical Discriminant Analysis, reveals a number of clear differences in shape and size of plant organs between the four main geographic areas. These morphometric differences, furthermore, correlate well with differences in other, more qualitative, features. We thus recognize four geographically delimited species: C. europaeaSchipcz. in Europe, C. foetidaL. in Siberia and Mongolia, C. kashmiriana J. Compt. & Hedd. sp. nov.in Kashmir and C. maireiH. Lévl. in China. Two varieties, C. foetidavar. racemosaRegel and C. maireivar. foliolosa(P.K. Hsiao) J. Compt. & Hedd., are also recognized. Keys and brief descriptions are provided for all the taxa, and the distribution of each species is mapped.

A review of the role of grazing management on the growth and performance of white clover cultivars in lowland New Zealand pastures

The current state of knowledge of white clover clonal growth processes and defoliation management is reviewed, and general recommendations on grazing principals made. Defoliation frequency determines herbage productivity through the manipulation of size/ density compensation between plant organ size (leaves) and numbers of growth units (growing point density). Hence large-leaved cultivars (Pitau, Kopu, Aran) are generally more productive under rotational grazing, whereas small-leaved cultivars are better suited to frequently grazed or set stocked conditions (Tahora, Prestige). The key to persistence is high growing point density, and the development of large-leaved densely branched cultivars should have superior performance over a wider range of grazing managements (Demand, Sustain). Grasses (perennial ryegrass, cocksfoot and tall fescue) grow by similar clonal processes to white clover and react in a similar manner to grazing management. Maintenance of pasture density (growing points/tillers) is crucial to persistence and is best achieved by rapid rotations or set stocking during spring/early summer. This provides protection against drought, and allows better exploitation of the genetic potential of species and cultivars through alternative grazing strategies over the remainder of the year. Keywords: clonal growth, cultivars, grazing management, morphology, populations, rotational grazing, seasonal growth patterns, set stocking, Trifolium repens L., white clover

Partitioning of Biomass in Well‐Watered and Water‐Stressed Cotton Plants Treated with Mepiquat Chloride

Most of the research investigating the effect of mepiquat chloride (1,1‐dimethylpiperidinium chloride) on the growth of cotton (Gossypium hirsutum L.) has been limited to well‐irrigated plants and has been focused primarily on the growth of aboveground organs. This study was conducted to evaluate the effect of mepiquat chloride (MC) on the partitioning of biomass in whole cotton plants grown in controlled‐environment test chambers under well‐irrigated and water‐deficient conditions. Single plants of ‘Stoneville 825’ were transferred from a nursery room into test chambers when they reached a leaf area of ≈500 cm2 and were then exposed to the following treatments: (i) sprayed at a recommended rate for commercial crops with 12 ± 1 mL plant−1 of a MC solution (27.3 mg L−1 a.i.) and maintained well irrigated, (ii) not sprayed with MC and maintained well irrigated, (iii) sprayed with MC and not irrigated, and (iv) not sprayed with MC and not irrigated. Durations of experiments varied from 11 to 14 d. Tests were replicated four times. Environmental conditions in the test chambers were typical of sunny and humid summer days in central Texas. Leaf area was measured daily during the tests. At the end of each test, the plants were harvested and separated into various categories of plant organs, oven‐dried and weighed. Water deficits inhibited the accumulation of plant biomass through inhibition of leaf lamina, petiole, and branch growth. The MC, on the other hand, did not affect the accumulation of biomass on a whole‐plant basis, but did affect biomass partitioning by inhibiting growth of branches and stem and by promoting growth of fine roots; MC also inhibited expansion of leaves and extension of stem internodes and petioles, which led to the development of a more compact canopy structure. These effects of MC on biomass partitioning and size of plant organs may result in decreased plant photosynthesis rates, but also may induce a water‐conservative behavior.

Shoot responses of young red pine to watering applied over two seasons

Young red pine (Pinus resinosa Ait.) trees were grown under three watering treatments from late summer until early fall and under two watering treatments again the next spring. Size of apical buds, date of bud swell and bud burst in the spring, number of needle fascicles on the new shoots, shoot length, and needle-fascicle spacing were related to the first treatments. Most of these plant responses were correlated with bud size, and the correlations were unaffected by the spring watering treatments. The effect of treatments was on magnitude only, i.e. on mean sizes or mean numbers of the plant organs.In all cases in this experiment watering treatments during elongation had no effect on the results. Therefore in a species such as red pine, with determinate height growth, environment during bud formation played an important role in determining later shoot responses by acting on the bud size.Possibly the relationships reported here are genetically characteristic, unalterable by environment or at least by water alone. In this case the effect of environment on the trees was a proportionate increase or decrease in the size or number of plant organs.

The Relation between Body Size and Organ Size in Plants

1. The problem of the relationship between the size of the plant body and the size of the organs it produces has been studied by various workers, who find that in most cases there is a small but significant correlation between these characters. 2. In a series of bean plants, the coefficients of correlation were determined between plant size, as measured by dry weight of shoot, dry weight of fruit, number of leaves, number of pods and number of seeds; and the average dry weight per plant of leaf, pod and seed. A positive and significant correlation, though usually a small one, was found in each case. 3. An examination of the curve of means for organ size on plant size shows that in each case the curve rises steeply at first and then flattens out. In other words, an increase in the size of the plant is accompanied by an increase in the size of its organs if we consider comparatively small plants only; but after a certain size is reached, any further increase in plant size is not followed by increase in organ size. Separate correlations between plant size and organ size made for small plants (those below the point where the curve flattens) and for large ones (those above it) showed a very decided correlation in the former and practically none at all in the latter. 4. These facts suggested that the size of an organ may not be correlated with body size at all, but rather with the size of the axial growing point from which it develops. In support of this idea attention is called to the fact that during the early stages of a plant's growth there is up to a certain point a progressive and parallel increase in the size of the plant and in the size of the primary meristems of its axes; but that after this point is reached meristem size remains constant and further increase in body size is not accompanied by any increase at all in that of the growing point. 5. Favorable material to test this hypothesis directly was afforded by twigs and leaves of Acer saccharum. The correlation between the blade volume of a given leaf pair and the cross-sectional area of the pith of the internode below (used as an index to the size of the growing point from which the leaves had developed) was found to be high (+ .807 ± .024). 6. It is therefore concluded that the size of a plant organ (leaf, fruit or seed) is dependent not upon the body size of the plant on which it is borne, but rather upon the size of the growing point from which it developed.