Anatomical Study of the Anthurium Plant (Anthrurium Andreanum L.) and a Color Breakdown Disorder of its Flower

Higaki, Tadashi
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Section I The gross morphology and anatomy study on Anthurium andreanum, L., was by whole plant observation, using dissecting and light microscope, and scanning electron microscopy. Anthurium is a perennial-herbaceous monocotyledon in the family Araceae. It is low growing with chordate leaves and attractive chordate flowers. It has a juvenile phase when each leaf axil has a lateral vegetative bud and a generative phase when each leaf axil has a flower and the lateral vegetative bud is located opposite the leaf attachment. The "commercial flower" consists of conspicious bract (spathe) and a protruding rachis (spadix Minute, botanically perfect flowers are borne spirally on the spadix. The flowers are protogynous as the stigma is receptive one week before shedding of pollen. Anatomically, the spathe has a one cell layered upper and lower epidermis, with 1 or 2 layers of hypodermis cells. Between the upper and lower hypodermis are 10-12 layers of spongy parenchyma cells. Vascular bundles are dispersed uniformly throughout the spathe. Anthocyanin pigments are localized in the hypodermal cells. The leaf blade is similar in structure to the spathe, except there is no hypodermis, but two layers of palisade parenchyma cells form the tissue immediately below the epidermis. Cholorplasts were dispersed throughout the mesophyll, but concentrated in the palisade cells. The pedicel, petiole and vegetative stem are typically monocot. Outer epidermal cells covered the cortex, a layer of sclerified parenchyma cells and the ground tissue. Vascular bundles were dispersed throughout the ground tissue. Roots were cylindrical, fleshy, epiphytic and adventitious. They were characterized by having multiple layers of epidermal cells called the velamen. Raphide and druse crystals were found scattered throughout the entire plant tissue. Above ground parts were covered with a thick waxy layer of cuticle. Section II A color breakdown disorder in the spathe of Anthurium andreanum, L., was investigated. Ca deficiency in the lobe section of the spathe was found to cause the disorder. Elemental analysis of spathe and leaf tissue of color breakdown and normal plants revealed lower Ca in color breakdown plants (color breakdown - spathe: 0.372%, leaves: 0.363%; normal - spathe: 0.830%, leaves: 0.805%). Electron microprobe X-ray analysis revealed lower Ca in lobe than tip section of the spathe and higher Ca in epidermal than mesophyll tissue. Nutrient culture studies produced color breakdown symptoms in the spathe with No Ca treatment. Symptoms were tiny water-soaked lesions the size of pin heads on the upper epidermal surface of the spathe lobe. The dots multiplied, increased in size and eventually coalesced to form large water-soaked lesions. The lesions dehydrated and turned brown. pH levels 3, 4, 5, 6, and 7 of complete nutrient solutions did not produce color breakdown in the spathe, although elemental chemical analysis of spathe and leaf tissues indicated lower Ca uptake of 3 and 4, higher at 6, and highest at pH 7. Lower Ca was found in the lobe than tip sections of both spathe and leaves, regardless of treatment. In a separate study, X-ray analysis produced similar results. In addition pH 9 gave lower uptake of Ca than 7. Microautoradiography study showed that calcium was deposited primarily in the cell wall. A field test with different Ca sources confirmed that the application of Ca significantly reduced the incidence of the disorder. A critical level of Ca within the tissue of the spathe is suggested with respect to the disorder. The critical level may be very narrow, but must be exceeded if tissue does not exhibit color breakdown. The critical level may be mediated by environmental conditions such as humidity and temperature. Like oedema disorder which is correlated with environmental conditions which hinder the normal transpiration processes of the plant, anthurium color breakdown may similarly be related to transpiration. Unlike oedema, however, the critical level of Ca in the lobe of the spathe is the major factor in the anthurium color breakdown disorder. Anatomical studies of color breakdown and normal flowers showed collapsing mesophyll cells in affected spathe. Separation of cells, when present on the permanent slides, suggested breakdown of the middle lamella due to lack of Ca. No sign of hypertrophy or intumescence was found.
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