Patterns of Growth and Development

It should surprise no one that the growth and development of plants should be influenced by heat and light. It is more interesting, and somewhat more difficult to demonstrate, that alternations of heat and cold, light and dark, may also influence the patterns of growth and development.

Responses to these alternating conditions vary among populations, allowing selection to adapt a population to the most reliable environmental conditions. If a species' bloom-time happens to concide with a period of strongly alternating day/night temperatures, the plants may exploit cell elongation to raise their stalks high enough to display their flowers to passing pollinators. But if the weather at bloom-time is not reliable, selection may favor a reduced response to day/night temperatures, forcing the plants to opt for increased cell division—or for an increase in the number of nodes—to achieve the necessary height.

It is also worth noting that patterns of growth (e.g., response to environmental conditions) may differ among developmental phases. This is clearly seen in the Amaryllis. During the vegetative phase, the stem shows almost no elongation—the apical meristem remains safely within the bulb. But when an axial bud is induced to flower, there is a dramatic elongation of the first internode (the scape), but little in the second (between the two spathe valves).

Vernalization and Photoperiodism, p. 94 (1948)
Anatomical and Histological Changes in Relation to Vernalization and Photoperiodism
R. H. Roberts and B. Esther Struckmeyer
New Evidence:—
Changes in anatomical structure have appeared consistently with or prior to blossom induction when usual conditions are used. They have also been well in advance of blossom primordial. There remains the question of the anatomical history when blossoms are initiated under such unusual environmental treatments as reversed night temperatures (22), "temperature girdles," banding, and grafting (29).
      When plants which come to flower early under relatively warm night temperatures as, Cannabis sativa (hemp), Datura stramonium (Jimpson weed), Euphorbia pulcherrima (poinsettia), Glycine max (soybean, var. Biloxi), Nicotiana tabacum (tobacco var. Maryland Mammoth), Panicum milaceum (millet), Phaseolus vulgaris (kidney bean), Solanum capicastri (ornamental pepper), Xanthium echinatum (cocklebur) and Zea mays (corn) are transferred to an environment with a warm (75°F) dark period of 13 hours and cool light period (55°F) of 11 hours, they soon become nearly etiolated or at least produce new growths with very little green color (23). Such plants are of particular interest from the standpoint of the physiology of sexual reproduction. They differentiate and develop blossoms and may even set fruits at almost the same rates as normally green plants in cool nights and warm days. Long continued development is not usual with such pale plants but the initiation of sexual reproduction is not inhibited and only slightly delayed by a lack of green color.
      Examination of the stems of plants grown with warm nights and cool days discloses that they have an anatomical history parallel to those grown in cool night and warm day temperatures. While they have the thin-walled cells with slight inclusions which are typical of partly etiolated or shade-grown samples, reduced cambial activity preceded the appearance of primordia when the proper photoperiod was used to induce reproduction.

Poinsettia plants in short days, but too warm at night to initiate blossom, can also be brought into blossom by wrapping taut rubber bands about the stems near the tips. When blossoming is induced in this manner, characteristic changes in the anatomical structure were found to occur above the point of banding.

Annals of the Missouri Botanical Garden 31: 241-247 (1944)
A Method for Recording and Analyzing Variations of Internode Pattern
Edgar Anderson and Dorothy Schregardus
This paper is an attempt "to make measurable that which has not yet been measured," the general habit of a plant. Those systematists who are also good field naturalists are often intrigued by the fact that closely related species of plants are commonly recognizable, even at a distance, by their peculiarities of habit, which are often more reliable than any single characteristic. But habit is difficult to convey to others and difficult to phrase concisely for a key or a technical description. It is based upon a number of things: the size, shape, positions, and textures of the leaves and the internode patterns of the vegetative shoot and the inflorescence. This paper provides an objective means for the analysis of variation in the latter.

Fig. 3. Effect of low (12 °C) and normal (18 °C) temperature on development of lateral shoots of the infloresence in 'Baccara' (hybrid tea) and 'Fire King' (floribunda). From left: 'Baccara' 12 °C, 'Baccara' 18 °C and 'Fire King' 12 °C.

Twelfth African Symposium on Horticultural Crops: Nairobi, Kenya, 1988
Growth and Flowering in Roses
R. Moe
    The effects of temperature and light quality on apical dominance (bud sprouting) and flowering in some greenhouse rose cultivars were studied.
    Increasing temperature hastened flowering and the number of flowers in each flush was increased. At 18°C, 3-3.5 times more flowers per plant were harvested, compared with a constant temperature of 12°C, due to lower blind shoot formation at high temperature. With fluctuating day and night temperatures, an average temperature of 18°C produced approximately the same yield as a constant temperature of 18°C. Low temperatures released apical dominance and stimulated lateral shoot branching.
    Day extension lighting with incandescent lamps (low R:FR ratio) inhibited lateral bud growth and induced blind shoot formation, while lighting with fluorescent lamps (high R:FR ratio) had the opposite effect. The use of red (R) and far-red (FR) lighting showed that FR inhibition of bud growth and flowering could be overcome by subsequent R lighting. These findings indicate that blind shoot formation is controlled by the phytochrome. The role of temperature and light quality on the assimilate supply to the buds and young shoots for optimum bud sprouting and flowering will be discussed.
    [CybeRose note: Firminger (1874) wrote of the 'Rose Edouard' that, "during the Cold season it produces flower-buds in unbounded profusion, which rot in the centre, and never open." Furthermore, according to "B.S.H." (1885), this variety "has, however, one unfortunate defect, which it too frequently transmits to the plants worked on it, that is, that during the cold season it almost invariably refuses to expand its blooms." This suggests that the action of the phytochrome mentioned above by Moe originates in, or acts through, the rootstock.]

J. Expt. Bot. 45(276):1019-1025.
Day/night temperature environment affects cell elongation but not division in Lilium longiflorum Thunb.
John Erwin, Peter Velguth and Royal Heins
Lilium longiflorum Thunb. cv. 'Nellie White' plants were grown in different day/night temperature (DT/NT) environments to determine the anatomical basis for differential responses of stem elongation to DT and NT. Lilium plants were forced in 1986 and 1987 under 25 and 12 different DT/NT environments, respectively, with temperatures ranging from 14 to 30°C. Parenchyma and epidermal cell length and width were measured in stem tissue (1987) and epidermal cell length and width were measured in leaf tissue (1986). Total cell number per internode and vertical cell number per internode were calculated. Stem parenchyma and stem and leaf epidermal cell length increased linearly as the difference (DIF) between DT and NT increased (DIF = DT - NT), i.e. as DT increased relative to NT. DIF had no effect on stem parenchyma width, stem and leaf epidermal cell width, or cell number per internode. Data suggested that stem elongation responses to DIF are elicited primarily through effects on cell elongation and not division.

HortTechnology October – December 1998 8(4)
Controlling Height with Temperature
Robert Berghage
SUMMARY. Temperature management has emerged as an important tool for plant height control in greenhouse production systems. This is particularly important in vegetable transplant production where chemical controls for plant height are limited or not legal. Plant height is a function of the number of nodes and the length of each internode, and both are strongly influenced by greenhouse temperatures., Node number, or formation rate, is primarily a function of the average greenhouse temperature, increasing as the average temperature increases. Internode length is strongly influenced by the relationship between the day and night temperature, commonly referred to as DIF (day temperature-night temperature). As DIF increases, so does internode length in most plant species studied. Although the nature and magnitude of temperature effects vary with species, cultivar, and environmental conditions, these two basic responses can be used to modify transplant growth. Although data are limited, controlling transplant height with temperature does not appear to adversely influence plant establishment or subsequent yield.
    In the 1980s, a number of research groups in the United States and Europe began to reexamine the effects of temperature on the growth of plants in the greenhouse. The primary objective of these studies was to provide commercial producers with the information needed to take full advantage of the new control technologies (i.e., Karlsson et al., 1983). During one of these studies, while examining the effects of day and night temperatures between 14 and 30°C on growth of Easter Lily (Lilium longiflorum Thunb.), it was observed that there was an interaction between day and night temperature that affected stem length (Erwin et al., 1989). This response was fit to a series of mathematical models. It was discovered that the interaction could be described with a single term made up of the day temperature minus the night temperature. This approach was then applied to a number of other crops including Went's (1944, 1957) tomato (Lycopersicon esculentum Mill.) data. It quickly became apparent that this relationship, coined DIF (Erwin et al., 1989), could be used to describe much of the stem elongation response to diurnal thermoperiod and photoperiod interactions (Erwin et al., 1989; Karlsson et al., 1989, Berghage and Heins, 1991). Subsequent research has shown near universality of the general response (Erwin and Heins, 1995), but it has also demonstrated that the magnitude, and nature of the thermomorphogenic effects varies between plant species, and among cultivars within a species, as well as with timing and duration of the temperature fluctuations (Erwin and Heins, 1995; Myster and Moe, 1995; Vogelezang et al., 1992).

Greenhouse Product News 9(4) (April 2009)
Controlling Height with Temperature Drops
Erik Runkle
Temperature drop is the practice of lowering the temperature, typically by 5-15° F, before sunrise for a two- to three-hour period. Generally, the greater the magnitude of the temperature drop, the stronger its effect on plant height. For the best and most consistent results, the temperature drop must be achieved before plants perceive the start of the day. Therefore, a common goal is to attain the desired temperature-drop setpoint 30 minutes before sunrise. Temperature drops are generally not effective when delivered at other times of the day or night.

Oecologia 103(2): 148-156 (1995)
Phenotypic plasticity in Cardamine flexuosa: variation among populations in plastic response to chilling treatments and photoperiods
Hiroshi Kudoh, Yoshio Ishiguri and Shoichi Kawano
Abstract: Variability in the plastic responses of seven life history traits to different chilling and photoperiod regimes was studied in four wild populations of Cardamine flexuosa. This species, a winter-green or year-long annual, showed a facultative long-day and chilling requirement for flowering. Considerable variation among populations was noted in plasticity of all traits. Differences in plasticity were greater among three paddy field populations from different climatic areas than between adjacent populations under different disturbance regimes. A paddy field population (OP) and an adjacent orchard population (OG) exhibited similar plasticity, in both amounts and patterns of response. TP, a Japan Sea coast population, was distinct from three other populations, especially in the small amounts of plasticity. Differences in amount of response were much more common than differences in pattern of response. Character expressions of five traits were significantly correlated with the number of days to flowering. Days to flowering and the numbers of inflorescences and siliques showed high negative correlations because the branching ability of meristems decreased with delay of flowering.

The Evolution of Plant Ecophysiological Traits: Recent Advances and Future Directions
Lechowicz and Wang (1998) have conducted one of the few studies evaluating phenotypic plasticity in a phylogenetic context (see also Pigliucci et al. 1999). In a study of 16 species of North American spruce growing in ambient and elevated CO2 and low and high water availability, they found that interspecific variation in many morphological and ecophysiological traits was not associated with the species’ phylogenetic relationships. However, relative growth rate, which is the outcome of interactions among many ecophysiological traits, showed consistent evolutionary trends across species. Perhaps most interesting, relative growth rate was also less plastic across environments than the many ecophysiological traits underlying variation in growth, but the levels of plasticity in growth rate did not themselves show any pattern of phylogenetic constraint. Evolution of function in extant spruces has apparently involved different patterns of diversification in the mean value of traits affecting growth and in the plastic expression of these traits in differing environmental regimes.

Lechowicz M, Wang ZM. 1998. Comparative ecology of seedling spruces: A phylogenetic perspective on adaptation. Page 16. Ecological Society of America, 83rd Annual Meeting, Abstracts
There are some 35 species of spruce (Pinaceae: Picea) worldwide, mostly in north temperate and boreal habitats. Some are widespread and commercially important, others are local endemics. The species vary substantially in their edaphic and climatic distributions. Given the ecological diversity represented and the reasonably well-defined phylogenetic relationships in Picea, the genus lends itself to comparative analyses of adaptation. We will present the results of an analysis of the responses of 16 spruce species grown under factorial combinations of (1) ambient and elevated CO2 and (2) low and high water availability. The species studied represent all the main lines of evolution within the genus. We consider the degree to which the characteristics of the different species represent shared ancesral traits versus possible adaptation to their different contemporary environments.

Published in Crop Sci 26:668-671 (1986)
Effect of Temperature and Photoperiod on Resistance to Purple Leaf Spot in Orchardgrass
C. C. Berg, K. E. Zeiders and R. T. Sherwood
Experiments were conducted to determine whether resistance of orchardgrass (Dactylis glomerata L.) to purple leaf spot (caused by Stagonospora arenaria Sacc.) is environmentally stable. Regrowth leaves of 60 greenhouse-grown genotypes were produced at four environmentally different dates (March, June, October, December) and were artificially inoculated. Spot size and spot frequency were scored on scales of 1 (no disease) to 8 (very severe disease). Plants scored <3.5 for either criterion were classified resistant. Only two of the 60 genotypes were resistant at all dates. Five genotypes were resistant at one or more dates, but moderately susceptible on at least one date. A significant genotype x environment variance indicated resistance of these five genotypes was unstable. Three genotypes that were classified unstable and one genotype each that was classified resistant, intermediate, or susceptible, were then grown in combinations of temperature and photoperiods as follows: i) warm, short day; ii) warm, long day; iii) cool, short day; and iv) cool, long day. They were inoculated and incubated 48 h in the dark at 22°C and returned to their respective greenhouse or growth chamber environments in three trials. All genotypes formed moderately-large to large spots in warm, short days, and all but the susceptible genotype formed small spots in cool, long days. The genotypes showed significant interactions with temperature or photoperiod for spot size and frequency. Repetitive artificial inoculations of genotypes during greenhouse screening programs may contribute to germplasm improvement by detecting and eliminating environmentally unstable genotypes.

Annals of Botany 51: 481-489, 1983
Photoperiod and Temperature Regulation of Floral Initiation and Anthesis in Soya Bean
Judith F. Thomas and C. D. Raper, Jr.
Floral development includes initiation of floral primordia and subsequent anthesis as discrete events, even though in many investigations only anthesis is considered. For 'Ransom' soya bean [Glycine max (L.) Merrill] grown at day/night temperatures of 18/14, 22/18, 26/22, 30/26, and 34/30 °C and exposed to photoperiods of 10, 12, 14, 15, and 16 h, time of anthesis ranged from less than 21 days after exposure at the shorter photoperiods and warmer temperatures to more than 60 days at longer photoperiods and cooler temperatures. For all temperature regimes, however, floral primordia were initiated under shorter photoperiods within 3 to 5 days after exposure and after not more than 7 to 10 days exposure to longer photoperiods. Once initiation had begun, time required for differentiation of individual floral primordia and the duration of leaf initiation at shoot apices increased with increasing length of photoperiod. While production of nodes ceased abruptly under photoperiods of 10 and 12 h, new nodes continued to be formed concurrently with initiation of axillary floral primordia under photoperiods of 14, 15 and 16 h. The vegetative condition at the main stem shoot apex was prolonged under the three longer photoperiods and is suggestive of the existence of an intermediate apex under these conditions. The results indicate that initiation and anthesis are controlled independently rather than collectively by photoperiod, and that floral initiation consists of two independent steps—one for the first-initiated flower in an axil of a main stem leaf and a second for transformation of the terminal shoot apex from the vegetative to reproductive condition.