Water relations and horticulture HORT 301: Plant Physiology Mike Mickelbart

Lecture outline Who cares about water? Review water movement in plants Examples of water relations in horticulture

Drought U.S.

The Kettleman Hills near the town of Kettleman City, California, along I-5, May Normally, the hills would be green at this time, but less than 1 inch of rain has fallen since January 1, and no annual grasses grew this year.

Barren River Lake, Barren Co, Kentucky, June 16, Reservoir 7.5 feet below summer pool, due to inadequate precipitation throughout the winter and spring seasons. Photo courtesy of Stu Foster.

Franklin, Tennessee, Aug 27, days with temperatures at or above 100°F, Water restrictions currently in effect. Photo courtesy of Jordan Gerth.

Drought

Source: Tucson Weekly

Drought Global Recent articles Scarce water and population boom leads California to 'perfect drought' Jun · No rain forecast in south of state until September · Sprinklers and car washing could be stopped Turkey rations water as cities hit by drought Aug Turkey's two major cities are grappling with water shortages after record low levels of snow and rain in the winter and searing summer temperatures. Darfur conflict heralds era of wars triggered by climate change, UN report warns Jun · Drought and advancing desert blamed for tensions · Chad and southern Africa also at risk from warming Source: Guardian Unlimited

The main question How does water move into and out of plants?

The main question How does water move into and out of plants? –Driving force = water potential

The main question How does water move into and out of plants? –Driving force = water potential

The main question How does water move into and out of plants? –Driving force = water potential –Series of resistances Leaf

The main question How does water move into and out of plants? –Driving force = water potential –Series of resistances Leaf Xylem Root Soil

Examples of water relations in horticulture Irrigation scheduling Fruit production Greenhouse management Stress monitoring in vineyards Evaporative cooling Transplant shock Partial root zone drying Saline irrigation water Water use efficiency

Fruit growth Turgor essential for fruit growth –fruit create water stress in trees –excessive turgor leads to splitting Splitting in fruits –Changes in turgor –Cell wall elasticity Turgor potential drives growth (1/V)(dV/dt) =  (P-Y) V = volume  = cell wall extensibility P = turgor pressure Y = yield threshold ©Ed Hume Enterprises

Greenhouse management Relative humidity Water uptake Plant cooling Nutrient uptake Air flow Boundary layer

Blossom end rot

Identification of stress

Vineyard stress monitoring

Evaporative cooling Average temps for parts of apple tree during 156 h overhead sprinkling Mean temp Irrigationairbarkleaffruit Overtree Undertree Nonirrigated

Transplant shock Soil differences

Water use efficiency (WUE) Definition –Mass/water Mass –Total biomass –Above-ground biomass –Yield Fruit Flowers Grain Others Scales –Ecosystem –Field/Greenhouse –Landscape –Plant –Leaf

Irrigation Irrigation efficiencies –Ea –Eu Irrigation application considerations –ET –Uniformity –Timing –Crop requirements

Partial root zone drying VarietyVariableControlPRD Shiraz Yield (t/ha) Water (Ml/ha) Yield/water Cabernet sauvignon Yield (t/ha) Water (Ml/ha) Yield/water Riesling Yield (t/ha) Water (Ml/ha) Yield/water Riesling Yield (t/ha) Water (Ml/ha) Yield/water Yield and water use of winegrapes McCarthy, 2000

Partial root zone drying

Water use efficiency Plant WUE –Species

Water use efficiency Plant WUE –Within species P. deltoides x P. maximowicziiP. nigra x P. maximowiczii

Examples of water relations in horticulture Irrigation scheduling Fruit production Greenhouse management Stress monitoring in vineyards Evaporative cooling Transplant shock Partial root zone drying Saline irrigation water Water use efficiency