Nastic Movements

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Nastic Movements


movements of leaves, petals, and other plant organs in response to stimulation, for example light and temperature. Such movements lack a definite direction. They result from the unequal growth of cells on the upper and lower sides of an organ or from uneven changes in the turgor of the cells. More intensive growth of the upper side of an organ —as in bud-unfolding or blossoming—is known as epinasty. Such accelerated growth on the underside—as in the closing of flower integuments after blossoming—is called hyponasty.

Different stimulants cause various other types of nastic movements. Photonasty, the movement of leaves and petals caused by changes in light intensity, characterizes snowdrops, water lilies, dandelions, and other plants. Thermonasty is caused by variations in temperature and is observed in crocuses and tulips. Nyctinasty, which is associated with diurnal changes, causes leaf and petal movement in many plants. Nyctinastic movements are combinations of photonastic and thermonastic movements. Seismonasty is movement of plant organs is response to mechanical stimuli or vibrations (for example, the movement of the stigmata and the anther stalks in certain insect-pollinated plants and the movement of leaves in insectivorous plants and in such sensitive plants as Mimosa pudica). Chemonasty, which is caused by small amounts of such gas-forming substances as ethylene, acetylene, and CO, effects leaf movement and the movement of other organs in sweet peas, tomatoes, and other plants.

The biological importance of nastic movements varies. In many plants, they are associated with adaptations for cross-pollination by insects and serve to protect the flowers from unfavorable conditions. In insectivorous plants, the movements aid in the trapping of insects. Some nastic movements are dependent on the presence of myosin-type contractile proteins in the cytoplasm.

References in periodicals archive ?
The introductory chapter is an overview of plant nastic responses as models for mechanical structures.
com, and MSN Live Search, find more information by searching for these words or phrases: plant growth and development, photoperiod, phytochrome, plant biological clocks, short-day plants, long-day plants, day neutral plants, plant hormones, auxin, IAA, parthenocarpic fruit, apical, gibberellins, bioassay, cytokinins, abscisic acid, ethylene, postharvest physiology, flowering hormone, tropisms, and nastic movements.
com/research/6xfltm/plants_and_mechani) has announced the addition of the "Plants and Mechanical Motion: A Synthetic Approach to Nastic Materials and Structures" book to their offering.
Stanford has Humphrey and 6-11 senior Stefan Nastic up front and senior all-conference guard Chasson Randle, who is averaging 19.
Nastic 5-7 5-7 15, Randle 5-21 8-11 21, Brown 1-5 1-2 4, Huestis 5-11 2-2 13, Powell 6-9 5-7 17, Rimmer 0, Mal.
nastic movements: Movement of plant parts in response either to certain external stimuli or to internal growth stimuli; generally slow.
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Chapter 23: Tropisms and Nastic Movements: Orienting Plants in Space.
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Dwight Powell added 17 and Stefan Nastic -- who fouled out with more than five minutes left -- had 15.