Main characteristics of vegetative plant growth

Pineapple is grown from a variety of propag-ules (see Hepton, Chapter 6, this volume) but all develop in a similar manner. If conditions for growth are favourable after planting, root initiation begins, followed by the appearance of new leaves. Between planting and inflorescence initiation, growth occurs in the root, stem and leaf meristems. Pineapple varieties that have strong apical dominance, such as 'Smooth Cayenne', generally do not produce shoots from stem axillary buds prior to flower induction, and shoots are typically not produced by 'Smooth Cayenne' in warm tropical environments until after fruit harvest. 'Queen Victoria' (Maerere, 1997) and 'Red Spanish' have weaker apical dominance and may initiate shoots prior to flower induction, even in tropical environments.

Shoots of the same initial mass, whether suckers or crowns, have approximately the same leaf area despite quite large differences in leaf number and size. Crowns have numerous short leaves, while suckers have fewer but longer leaves. In an experiment in Côte d'Ivoire, the leaf appearance rate in the month after planting was 8 for crowns and 3 for suckers (Lacoeuilhe, 1976). Beyond 3 months, leaf emergence rate was similar for crowns and suckers. During the first few months of growth, leaves produced by suckers are longer and heavier than those produced by crowns. For planting material of similar size, leaf emergence rate and leaf size are similar within 3-5 months after planting (Py et al, 1987).

Leaves

Leaves represent approximately 90% of aerial plant fresh weight during vegetative growth (Py, 1959). Leaves grow from the base, the maximum leaf length is reached several months after initiation and leaves of a wide range of sizes and ages are present on the plant at the same time (Fig. 5.5). The time from initiation to full elongation depends on temperature and is approximately 4 months in the nearly equatorial conditions of Côte d'Ivoire, but considerably longer in cooler environments. Sideris and Krauss (1936) separated pineapple leaves into categories based on their similarity in size and age. The 'D' group of leaves were the longest on the plant and had 'succulent-brittle' leaf bases. Over time it became common practice to apply the term 'D' to a single leaf, usually the tallest leaf on the plant. This 'D' leaf represents an easily identified standard leaf (Fig. 5.6) that is commonly used to index growth and evalu

Fig. 5.5. Array of leaves present on a fruiting pineapple plant. The oldest leaves are to the right of the stem and its associated peduncle and fruit. (Photo of E. Malezieux.)

ate plant nutrient status. When growth is rapid, the tallest leaf is almost always nearly but not fully expanded (Py et al, 1987). When growth is unrestricted by stress, the maximum length, width, and weight of individual leaves increase with each successive leaf until a maximum is reached (Fig. 5.5). Maximum leaf length may differ among pineapple varieties, but, for 'Smooth Cayenne', the maximum length can reach 100 cm and the maximum width can reach 7 cm (Py et al., 1987). Total leaf area per plant can reach 2.2 m2 for a plant having a fresh weight of 3.6 kg (Py, 1959). The LAI of a pineapple canopy can reach 12 at floral induction, although values of 6-8 are more common.

Roots

Few data are available on root growth. Though roots of 'Smooth Cayenne' pineapple can theoretically reach a length of 1.8 m and grow to a depth of 85 cm (Sideris and Krauss, 1934), the sensitivity of pineapple roots to soil compaction (Rafaillac et al., 1978; Ikan, 1990) generally confines the root system to the tilled area (Ekern, 1965; Ikan, 1990; J.J. Lacoeuilhe and E. Malezieux, unpublished results). This restricted soil volume prospected by the roots can limit the amount of water available to the plant. After planting, crowns produce more roots than suckers (Py et al., 1987). There is evidence

Leaf Pineapple

Fig. 5.6. The pineapple 'D' leaf is most accurately identified by the more or less parallel margins of the leaf base as contrasted with the flared base of the older 'C' leaf on the left and the tapered base of the young 'E' leaf on the right. For mineral-nutrient analysis, the middle one-third of the basal white tissue is sampled. (Modified from Nightingale, 1949.)

Fig. 5.6. The pineapple 'D' leaf is most accurately identified by the more or less parallel margins of the leaf base as contrasted with the flared base of the older 'C' leaf on the left and the tapered base of the young 'E' leaf on the right. For mineral-nutrient analysis, the middle one-third of the basal white tissue is sampled. (Modified from Nightingale, 1949.)

that root growth decreases after flower induction and that maximum root mass is reached at anthesis.

Stem and axillary buds

Stem mass increases progressively after planting, with no unique morphological changes until reproductive development begins. Plants may accumulate starch reserves in the stem, but such accumulation varies with plant age and size and aerial environment. Soon after floral induction occurs in 'Smooth Cayenne', axillary bud development usually begins, but active growth is highly dependent upon climatic conditions. Axillary shoot growth occurs during fruit development on relatively large but not on small 'Smooth Cayenne' plants in subtropical conditions, but only after fruit harvest in tropical environments having warm night temperatures. This may be related to the higher starch content of the stem in plants growing in subtropical conditions, where the night temperature is cooler and the day/night temperature differential is larger. The growth of one to a few suckers makes possible the production of one or more second fruits on the mother plant (ratoon crop) and these shoots are also used as propagules.

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  • angelico
    What is the characteristic of pineapple roots?
    2 years ago

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