Plant Material Maintenance, chapter 2 in the text

Acer saccharumBetula nigraViburnum dentatum

 Crown: the branches, twigs and leaves of a tree or shrub.  Shoot: a young, actively growing stem.  Bud: an unexpanded shoot or flower (a dormant meristem) ◦ Leaf (Vegetative) ◦ Flower ◦ Mixed

 Meristems: Places in plants where cell division is occurring. ◦ Apical meristems are found in shoot tips and root tips. AM cause shoot and root lengthening. ◦ Vascular cambium causes diameter growth in stems and roots.

 Growth: the amount of growth experienced by an individual shoot depends on the rate of and duration of cell division and expansion.  Varies by species.

 Short (3-4 weeks) growth flush in the spring. ◦ Ex: Coniferous Evergreen plants and many deciduous plants.  Several growth flushes over a growing season. ◦ Ex: Monterey Pine and many species of oak.  Growth continues as long as conditions are favorable. ◦ Ex: Sweet Gum, Redwood, and Sugar Maple.

 Photosynthesis: Light Water Carbon Dioxide Chlorophyll (a green pigment found in leaves) Glucose (sugar; carbohydrate) Oxygen

 Holly leaves have a thick, waxy cuticle.

 Anchorage.  Absorption of water and mineral nutrients.  Storage of food reserves.  Synthesis of organic regulatory compounds.

Tree roots extend radially in every direction to a distance equal to at least the height of the tree (assuming no physical barriers) and grow predominantly near the soil surface. Typically 90% of all roots, and virtually all the large structural supporting roots, are in the upper 2-3 feet of the soil. This includes the small, feeder roots.

 Taproots are common on the dicots.  Fibrous root systems are common on the monocots. fibrous root system

 Translocation of water, nutrients, and sugars. ◦ Xylem: transports water and dissolved nutrients. ◦ Phloem: transports sugars ◦ Movement is from “source to sink”; that is from areas of high concentration to areas of low concentration.  Stems support the leaves and fruit.

 Roots that develop from newly organized meristems forming in stems, leaves, and other plant parts.

Adventitious roots developing from the leaf petiole of Peperomia. Adventitious roots developing from the stem of a Coleus cutting.

Adventitious roots forming on an Iris corm.

 Photosynthesis  Respiration  Transpiration

light

 Photosynthesis is occurring primarily in the leaves and green stems.  Respiration is occurring in all of the living cells of a plant; leaves, stems, and roots.

Oxygen Carbohydrates (sugars) Carbon dioxide Water Heat Chemical energy (ATP)

PHOTOSYNTHESIS Light and chlorophyll Water Carbon dioxide Oxygen RESPIRATION Carbon dioxide ATP Sugars Soil Minerals Absorbed with water Lignin Fats Proteins Enzymes Pigments Hormones Vitamins Starch Pectin Cellulose HEAT Water

 Soil pore space is filled with water.  No oxygen in the pore space.  Without oxygen the roots will die.  Without roots the plant can’t absorb water. ◦ Low areas ◦ Soil compaction ◦ Burm up the soil or drain the planting hole.

 On sunny, warm days the sun warms up the leaf surfaces.  The water in the cells of a leaf begins to evaporate.  Water vapor collects in the spongy mesophyll tissue of the leaf.  The water vapor moves out of spongy mesophyll, through the open stomata, and into the drier air surrounding the leaf.  As water evaporates from the spongy mesophyll, new water molecules are delivered to the leaf through the xylem in leaf veins.  Transpiration is a “pulling” force drawing water up the stem xylem and into the leaves.

The rate of transpiration is affected by the following 3 things: Humidity; during dry, less humid days the rate of transpiration increases. Temperature; the rate of transpiration is greater on hot days than on cooler, cloudy days. Wind; the rate of transpiration is greater on windy days than calmer days.

 Phototropism: a shoot will always grow towards a light source.  Geotropism: roots always grow down in response to gravity.