1BIOL 695PLANT GROWTHand CROP PRODUCTIONCHAPTER 5Mengel et al., 5th Ed GerminationInitiated by H2O &O2&PhytohormonesUtilizes CHO and amino acids fromseed Vegetative StageOlder leaves supply youngerMajor addition of biomass Reproductive StageFlower initiation then pollination MaturityPhotosynthates mostly to storage tissueESSENTIAL GROWTH STAGES2Specificcomponentsmay varyFood production/Food utilizationrelationshipschange as plantages;i.e., source:sinkRelationshipchangesGrowth StagesSink willChangeWithmaturitySOURCE - SINK RELATIONSHIP3(IAA)(GA)PHYTOHORMONESPHYTOHORMONES4 Biological Yield- total production of plant material Economic Yield- plant organs which are harvested Which plant types have:- biological =economic yield Which plant types have:- biological ?economic yieldGROWTH RATE &NUTRIENT SUPPLY Vegetative growth stage:- formation of new leaves, stems, roots- very active protein metabolism- most photosynthates used for synthesisof nucleic acids and proteins- N nutrition largely controls growth rate- carbohydrate accumul. gen later- amount of N must be in balancewith other parameters- nutrient balance very importantGROWTH RATE &NUTRIENT SUPPLY5EFFECT OFAUXINSGROWTH RATE &NUTRIENT SUPPLY Vegetative growth stage:- mineral nutrient requirement primarilydetermined by rate of CO2assimilation- temperature is very important; affectsgrowth rate more than lightGROWTH RATE &NUTRIENT SUPPLY6 Tuber initiation produced by hormones- ABA promotes; GA inhibits- ABA/GA ratio controls tuber setting Continuous supply of N low ABA/GA- regrowth of tubers (text, Plate 5.7) Decline in N supply increases ABA- normal tuber production Tuber filling also related to CHO supply N management:- vegetative stage - high N- tuber stage - declining N; maintain P, KROOT CROP NUTRITION MANAGEMENT Prior to fruit setting, need rich vegetativegrowth to build up food reserves Fruit setting related to phytohormones(ABA/IAA) and probably nutrition Fruit ripening food, nutrition (Ca) Temperature &light effects - less control Alternance - perennial fruit crops that tendto bear fruit only every 2nd season;especially noted in applesFRUIT CROP NUTRITION MANAGEMENT7 Synthetic plant hormones (bioregulators)TIBA - 2, 3, 5-triiodobenzoic acid- inhibits auxinsCCC - chlorocholine chloride- inhibits gibberellins Objectives:decrease stemelongation (why?)increase (extend) reproductive growthdecrease senescence &abscissionGROWTH REGULATORS Net assimilation =(Photosynthetic Prodn - Respiration) Difference between C3 &C4 plants:- no photorespiration in C4 plants- C4 plants show positive NAR at verylow CO2levels around leaf (5x