Wheat. Peter R. Shewry

Wheat

Soil water stored from monsoon. Temperate. 5A Spring High rainfall. Hot (coolest month > 17.5 °C). 5B Spring Irrigated. Hot. 6 Spring Moderate rainfall. Winter would kill wheat. Coolest month < –10 °C. 7 Facultative Irrigated. Cool. 8A Facultative, daylength sensitive High rainfall. Cool. 8B Facultative, daylength insensitive High rainfall. Cool. 9 Facultative Low rainfall (< 500 mm available to crop). Cool. 10A Winter Irrigated. Cold winter. 10B Winter Rainfall + irrigation. Cold winter. 11A Winter, daylength sensitive High rainfall. Cold winter. 11B Winter, daylength insensitive High rainfall. Cold winter. 12 Winter Low rainfall. Cold winter, hot summer.

The growth of wheat can be broadly divided into two phases: the vegetative phase and the reproductive phase. The distinction between the two phases depends on events in the bud tip, or stem apex (i.e. the apical meristem if referring to the main stem) of the plant. The vegetative phase encompasses germination, and then a period during which growth from the stem apex gives rise only to vegetative tissues: leaves, tillers (i.e. the branches or side stems of grass plants), and adventitious roots.

Table 1.4 Growth stage scores of wheat plants.

	Decimal growth stages (DGS) according to Zadoks et al. (1974)	The scale of Feekes (1941)
Major growth phases	Major division	Minor divisions described by n	Score	Description	Equivalent DGS score
Germination	0n	n indicates development before leaf emergence i.e. from dry seed (n = 0) to first leaf at coleoptile tip (n = 9)
Leaf production	1n	n is the number of unfolded leaves on the main stem to a max. n = 9	1	Seedling emergence to three leaf stage	10–13
Tiller production	2n	n is the number of tillers with their own unfolded leaf to a max. n = 9	2	Start of tillering	21–25
Tiller production	2n		3	End of tillering	26–29
Stem extension	3n	n is the number of nodes to a max. of 6, then n = 7 for flag leaf just visible, and n = 9 flag leaf unfolded	4	Leaf sheaths lengthen	30
			5	Leaf sheaths strongly erect	30
			6	One node detectable	31
			7	Two nodes detectable	32
			8	Flag leaf just visible	37
			9	Flag leaf emerged	39
Booting	4n	n indicates degree of swelling of the boot	10	Booting	45
Ear emergence	5n	n indicates proportion of ear or ears emerged	10.5	Full ear emergence	59
Anthesis	6n	n indicates degree of completion	10.51	Start of anthesis	60
Grain expansion	7n	i.e. droplet exuded when caryopsis squeezed changes from watery (n = 1) to milky (n = 7)	10.54	Caryopsis water ripe	71
Grain expansion	7n		11.1	Caryopsis milky ripe	75
Dough development	8n	i.e. no droplet exuded from squeezed caryopsis, thumbnail imprint not retained (n = 3) to thumbnail imprint retained (n = 5+)	11.2	Soft dough	85
Ripening	9n	Grain dry enough to harvest (n = 2) to seed with no primary dormancy (n = 7)	11.4	Harvest ripe	92

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